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1. 12 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 2 2 5 Annotations In order to provide extra information for the programming environment Self supports annotations on either whole ob jects or individual slots Although any object can be an annotation the Self syntax only supports the textual definition of string annotations In order to annotate an object use this syntax this object has one slot snort 17 In order to annotate a group of slots surround them with braces and insert the annotation after the opening brace Category accessing getOne getAnother anUnannotatedSlot Annotations may nest if so the Virtual Machine concatenates the annotations strings and inserts a separator character 16r7f 7 2 3 Expressions Expressions in Self are messages sent to some object the receiver Self message syntax is similar to Smalltalk s Self provides three basic kinds of messages unary messages binary messages and keyword messages Each has its own syntax associativity and precedence Each type of message can be sent either to an explicit or implicit receiver Productions expression constant unary message binary message keyword message expression y constant self number string object unary message receiver unary send resend unary send unary send identifier binary me
2. Lee88 Elgin Lee Object Storage and Inheritance for SELF Engineer s thesis Stanford University 1988 Ung84 David Ungar Generation Scavenging A Non Disruptive High Performance Storage Reclamation Algo rithm In Proceedings of the ACM SIGSOFT SIGPLAN Software Engineering Symposium on Practical Soft ware Development Environments Pittsburgh PA April 1984 Published as SIGPLAN Notices 19 5 May 1984 and Software Engineering Notes 9 3 May 1984 Ung86 David Ungar The Design and Evaluation of a High Performance Smalltalk System MIT Press Cambridge MA 1987 UCC91 David Ungar Craig Chambers Bay Wei Chang and Urs H lzle Organizing Programs without Classes In Lisp and Symbolic Computation 4 3 June 1991 US87 David Ungar and Randall B Smith SELF The Power of Simplicity In OOPSLA 87 Conference Proceed ings Orlando FL 1987 Published as SIGPLAN Notices 22 12 December 1987 Also published in Lisp and Symbolic Computation 4 3 June 1991 and as Sun Microsystems Labs TR SMLI 94 0320 134 Chapter 9 References CHAPTER TEN APPENDICES 10 1 Glossary e A slot is a name value pair The value of a slot is often called its contents e An object is composed of a possibly empty set of slots and optionally a series of expressions called code The Self implementation provides objects with indexable slots vectors via a set of primitives e A data object is an object without code e A data slo
3. The absolute minimum width and height of a morph even when it has no submorphs is specified by its baseMin Width and baseMinHeight For some kinds of morph these values are stored in assignable slots in the morph For others these values are defined by inherited constant slots to save space One can use these attributes to give a space filling morph a minimum size 98 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 7 7 5 Resize Attribute Summary The resizing behavior of a morph in one dimension is completely independent of its behavior in the other dimension that is a morph actually has two independent resizing attributes one for the horizontal dimension and one for the vertical dimension To summarize the resizing behavior of a morph along a given dimension is controlled by its resizing attribute which has one of three values rigid The morph is not resized space filling In a row or column the size of the morph adapts to fill the available space Extra space is shared evenly with any other space filling morphs in that row or column shrink wrap The morph is shrunk to just fit around its submorphs or to its minimum size whichever is smaller Enclosed space filling morphs are shrunk if necessary A morph s minimum size in a given dimension determines the smallest amount of space that should be allocated to it during layout The core sampler and or properties
4. aCategorizedMethod user Query report Hello there El aCategorizedVa able a 17 31 4 a subcategory who Ami F os environmentAt LOGNAME IfFail The Phantom IfFail The Phantom resize triangle 5 2 Browsing Concepts 49 Self Handbook Documentation Release 2 for Self 4 4 aCategorzedVar able YF 4a subcategory whoAmI mI green os environmentAt LOGNAME IfFail The Phantom red change the method AVE QUIZEUIVIE NODO USET AUETY Tepori MEHO ere d aCategonzed Vanable 17 3 4a subcategory who Ami mT os environmentAt LOGNAME fFail The Phantom Self text editors will honor the cursor arrow keys the copy paste and cut Sun keys and many emacs style control characters Table 1 Partial list of control characters in Self text editors Character Effect control a move to start of line control b back one character control d delete next character control e go to end of line control f forward one character control k kill to end of line control 1 expand the text editor to show the whole text control n go to next line control o open a new line after the cursor control p go to previous line control t transpose characters control w erase previous word control y yank text from past buffer to editor delete backspace or control h erase last character meta return command return on Mac accept escape also command period on Mac cancel meta s
5. 0 ee 39 4 2 Objects Have Many Roles 2 5 sae ra Reo 4 Be eee Oe ea a 40 4 3 Naming and Printme s s doh ett ne aie ae Oe i Bie A A e Bee ee 41 44 How to Return Multiple Values lt lt Gob eke eb ee eR A eee 42 45 Substituting Values tor Blocks 2 20642 284 46454 234644564554 404 2S 04 43 46 nid Considered Naughty 25 064 IEA A Eee Rg amp Ale es 43 47 Wash and oeno meni 556A see bie a seein eee ea etek bee seal E 44 4 8 Equality Identity and Indistinguishability o e e a e 44 How to Program in Self 45 Sil troduction enses s aaea e ER RE A AR A EA 45 a2 Browsme Concepts settee ea A AAA y AA A eee Ss 45 9 9 Hacking ODJEC S macia ao ae a ow a ks He A AA es Sd a4 The LIaMsporte ces mps an ee da A e e e ed a A Glossary of Useful Selectors Morphic The Self User Interface Framework DA OVERVIEW rr A Se ee eee ee a S 17 2 Composite Morphs i sio ee A Ae a ee ae we a oe a 7 3 Morph Traits and Prototypes so 45 44 ee a a E a a Bw al ew SG Y TA Savine a Composite Morph eiii e sors aa e ea a a BS BD an ws Bog Bow a 1 3 Handling User Input voor ar o Sb Oe bade Phe wee EA Ped ee ea A 76 Drag and DrOp ied eee eh Pet bs BA A ERE ee BAS TI Automatic layout ox ari E yA ee eK EA SR Ee a ge E ee So AAMIMANON vied e ERA GL ee ee A Ae amp RENO Oe a A Sade a RS 19 Other Issues c5 4 Se aoe ye Gu sob ee eed ed a ee ee be ad 710 Morph Responsibilities 4 4 05 244642
6. Hello there S aCategonzedVarable 173 4 a subcategory whoAml Sg os environmentAt LOGNAME IfFail The Phantom Getit Doi Close 5 2 Browsing Concepts 53 Self Handbook Documentation Release 2 for Self 4 4 4 anExampleObject AJE X Module programming Examples parent traits clonable anUncategonzed Constant 3 14159 anUncategorizedMethod user Query report Hello there El anUncategorized Variable a 173 4a category of slots aCategorizedConstant 3 14159 aCategorizedMethod user Query report Hello there El aCategorizedVar able EA 2 4 a subcategory whoAml amp os environmentAt LOGNAME IfFail The Phantom whoAmt 54 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4 anExampleO bject A El x Module programming Examples parent Traits clonable anUncategorizec Constant 3 14159 anUncategorized Method userQuery report Hello there 8 anUnc gable 47 gi aca AddSlot aCa Add Category Stant 3 14159 aCa Copy od user Query report Hello there E aCa _ Move ble i 3 4a s Set module whoAml o os environmentAt LOGNAME IfFail The Phantom whoAmI Gei Doit Close 5 2 Browsing Concepts 55 Self Handbook Documentation Release 2 for Self 4 4 4 anExampleO bject Aj Ejx Module programmingBbamples traits cl
7. Removed Slots Restore Window State Save snapshot Save snapshot as Save Window State Send Senders Senders of Senders in family Senders of in family Set Module Shell Show All Frame Show Annotation Show Comment Show Morph Subclass Me The box at the top Toggle Spy Traits Family Write Snapshot Open a new window containing handy morphs such as a radar view you can tear off and drag to other Self windows Summons an object for obtaining morphs for building Pastes text from the buffer Leave job and ride boxcars Summons an object for moving the current viewport around in space On a module morph rereads the source file Enumerate references to an object On a module morph lists removed slot paths Restores the saved state of the screen Saves an image of all objects in a snapshot file Overwrites the snapshot file that was opened originally Saves the previous version with a old suffix Lets you set the file name and other parameters of the saved snapshot For example if you have a lot of memory you can increase the code cache size Saves the state of the screen For a method in a concrete object send the message to the object Searches for methods sending a given message For an assignable slot x show all senders of x i e methods that might assign to X Searches for methods sending a given message in the selected object its ancestors and it descendants For an assi
8. 2 3 8 The lookup algorithm The lookup algorithm recursively traverses the inheritance graph which can be an arbitrary graph including cyclic graphs No object is searched twice along any single path The search begins in the object itself and then continues to search every parent Parent slots are not evaluated during the lookup That is if a parent slot contains an object with code the code will not be executed the object will merely be searched for matching slots The function lookup obj sel V is defined as follows Input obj the object being searched for matching slots sel the message selector V the set of objects already visited along this path Output M the set of matching slots Algorithm if obj e V then M Y cycle detection else M s e obj s name sel try local slots if M then M parent_lookup obj sel V end try parent slots end return M Where parent_lookup obj sel V is defined as follows P amp s e obj s isParent all parents M v lookup s contents sel V v obj recursively search parents seP return M 2 3 Expressions 17 Self Handbook Documentation Release 2 for Self 4 4 2 3 9 Undirected Resend An undirected resend ignores the sending method holder the object containing the currently running method and continues with its parents The function undirected_resend rec smh sel args is defined as follows Input rec the rece
9. 89 Conference on Programming Language Design and Implementation Portland OR June 1989 Published as SIGPLAN Notices 24 7 July 1989 CU90 Craig Chambers and David Ungar Iterative Type Analysis and Extended Message Splitting Optimizing Dynamically Typed Object Oriented Programs In Proceedings of the SIGPLAN 90 Conference on Program ming Language Design and Implementation White Plains NY June 1990 Published as SIGPLAN Notices 25 6 June 1990 Also published in Lisp and Symbolic Computation 4 3 June 1991 CU91 Craig Chambers and David Ungar Making Pure Object Oriented Languages Practical In OOPSLA 91 Conference Proceedings Phoenix AZ October 1991 Published as SIGPLAN Notices 26 11 November 1991 CUC91 Craig Chambers David Ungar Bay Wei Chang and Urs H lzle Parents are Shared Parts of Objects Inheritance and Encapsulation in SELF In Lisp and Symbolic Computation 4 3 June 1991 CUL89 Craig Chambers David Ungar and Elgin Lee An Efficient Implementation of SELF a Dynamically Typed Object Oriented Language Based on Prototypes In OOPSLA 89 Conference Proceedings New Orleans LA October 1989 Published as SIGPLAN Notices 24 10 October 1989 Also published in Lisp and Symbolic Computation 4 3 June 1991 Cha92 Craig Chambers The Design and Implementation of the SELF Compiler an Optimizing Compiler for Object Oriented Programming Languages Ph D dissertation Computer Science Departme
10. The Self system The VM executes Self programs specified by objects in the Self world and provides a set of primitives which are methods written in C that can be invoked by Self methods to carry out basic operations like integer arithmetic 1 UNIX is a trademark of AT amp T Bell Laboratories Self Handbook Documentation Release 2 for Self 4 4 object copying and I O The Self world distributed with the VM is a collection of Self objects implementing various traits and prototypes like cloning traits and dictionaries These objects can be used or changed to implement your own programs transporter a ie ee SELF Source Code Na ig RunScript primitive gt S disk file parser a SELF Objects N cecilia C SELF Source Code gt SELF heap read eval print loop or ul keyboard gt fo Y G SELF Methods N a Compiled Method N objects with bytecodes F a er ne Y machine code E SELF heap not in the code cache Compiled code cache is called Figure 1 2 Figure 2 How Self programs are compiled Self programs are translated to machine code in a two stage process see Figure 2 Code typed in at the prompt through the user interface or read in from a file is parsed into Self objects Some of these objects are data objects others are methods Methods have their own behavior which they represent with bytecodes The bytecodes are the instructions for a very simple virtual pro
11. They consist of an identifier or a capitalized identifier followed by a colon Productions small keyword identifier cap keyword cap letter letter digit _ tas Examples at Put _IntAdd 2 4 4 Arguments A colon followed by an identifier denotes an argument slot name Productions arg name identifier 2 4 Lexical elements 19 Self Handbook Documentation Release 2 for Self 4 4 Example name 2 4 5 Operators An operator consists of a sequence of one or more of the following characters 1 RA amp 4 72 lt gt 51 Two sequences are reserved and are not operators A Productions op char gt PLE IPS 1D 118 1812112121917 EXI ISTRIA operator gt op char op char Examples amp amp I lt gt 2 4 6 Numbers Integer literals are written as a sequence of digits optionally prefixed with a minus sign and or a base No whitespace is allowed between a minus sign and the digit sequence Real constants may be either written in fixed point or exponential form Integers may be written using bases from 2 to 36 For bases greater than ten the characters a through z case insensitive represent digit values 10 through 35 The default base is decimal A non decimal number is prefixed by its base value specified as a decimal number followed by either r or
12. While this property not having special kinds of objects gives Self great flexibility and expressive power it leads to an interesting problem the inability to distinguish behavior that is ready for immediate use from that which is defined only for the benefit of descendant objects Put another way Self cannot distinguish those objects playing the role of classes from those playing the role of instances The most prominent manifestation of this problem crops up in object printing Suppose one wishes to provide the following printString method for all point objects 4 3 Naming and Printing 41 Self Handbook Documentation Release 2 for Self 4 4 printString x printString y printString Like other behavior that applies to all points the method should be put in point traits But what happens if printString is sent to the object traits point The printString method is found but it fails when it attempts to send x and y to itself because these slots are only defined in point objects not the traits point ob ject Of course there are many other messages defined in traits point that would also fail if they were sent to traits point rather than to a point object The reason printing is a bigger problem is that it is useful to have a general object printing facility to be used during debugging and system exploration To be as robust as possible this printing facility should not send printString when it will fail Unfortunately it
13. as for failure passed to the IfFail block at the call site in Self Warning After calling failure or unix_failure anormal return must be done The value returned in the example NULL is ignored 8 13 7 Reading and assigning global variables Reading the value of a global variable is done using the C_get_var macro Assigning a value to a global variable is done using C_set_var Both macros expand into a C function that converts between Self and C representation and reads or assigns the variable Here is the general syntax C_get_var cnvt_res aux_res expr gfname C_set_var var expr_c0 expr_a0 gfname A concrete example is reading the value of the variable errno which can be done using C_get_var int errno get_errno_glue The meaning of the each argument is e cnvt_res aux_res how to convert the value of the global variable that is being read to a Self object In the errno example cnvt_res is int and aux_res is empty since the type of errno is int The cnvt_res aux_res can be any one of the result conversions found in Table 3 e expr is the variable whose value is being read In the errno example it is simply errno but in general it may actually be any expression that is valid in a global context even an expression involving function calls e gfname the name of the C function that C_get_var or C_set_ var expands into e var is the name of a global variable that a value is assigne
14. command s on Mac save a snapshot meta x command x on Mac cut meta c command c on Mac copy meta v command v on Mac paste meta d command d on Mac dismiss morph containing typing focus 50 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 Dismissing Objects There are four separate ways of dismissing an outliner or for that matter anything from the Self desktop e Object outliners Push the X button at the top right hand corner e Drag it to the trash left drag on the outliner till the mouse is over the trash can then release the mouse button e Dismiss it via the right button menu hold down the right button over the outliner move to the Dismiss button then release e The Carpet Morph start above or below and to the left or to the right of the outliner over the background Hold down the left button and sweep out an area that completely contains the outliner then release the left button The outliner should now be surrounded by a rectangle Use the middle mouse button inside the rectangle to select Dismiss The last two methods dismissing from the right button menu and marquee selection with the carpet morph come in especially handy with things like buttons and menus because such morphs cannot be grabbed with the left button 5 2 2 Menus in the Outliner Many other operations are available on the outliner by using the middle button menu on the part of t
15. ovyalMorph type morph Add it anyway Omit from mpying dym 4ovalMorph type morph Creator slot ovallorph Complete Yes Ho Copydora parent morph Copydown selector copyRemoveAllMorphs lots to omit Modules morph morphoaving parent ars ovabier ph otherColor a pame t bios Mor ph State AUN oie prototype ovalifar ph a ovalHorkh Figure 7 10 Figure 10 Setting the copydown parent for the new prototype 4 globals 4 traits 117 Modules 108 Modules bapplications slots wats slots beollections bapplications bgraphics boollections Amy mor phs graphis ovalMorph ovalMor ph tupe ovalifor ph Amy mor phs Module ovalModule ovalMorph wats ovalMor ph Follow Initialize to Module ovalModule Psystem Follow Initialize to pui Ps wiem pui Figure 7 11 Figure 11 Setting the modules for the namespace slots The module will be created if it doesn t already exist the system asks the user several questions about where the new module should live and whether it is a submodule of some existing module 92 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 Add Slot Add Category Show C omnnment 4ovalMorphitype ovalMiorph Atraits Show Annotation Modules morph morphsaving Modu set module parent wats ovalMor ph parer Copied Down cha mn othercolor a pone 5 gt leaf t basel Show Traits Family a b Basic Mor ph State isRec Children le bing
16. the message selector is the concatenation 14 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 of the keywords forming the message Message selectors beginning with an underscore are reserved for primitives 2 3 7 Example 5 min 4 Max 7 is the single message min Max sent to 5 with arguments 4 and 7 whereas 5 min 4 max 7 involves two messages first the message max sent to 4 and taking 7 as its argument and then the message min sent to 5 taking the result of 4 max 7 as its argument Associativity Keyword messages associate from right to left so 5 min 6 min 7 Max 8 Max 9 min 10 Max 11 is interpreted as 5 min 6 min 7 Max 8 Max 9 min 10 Max 11 The association order and capitalization requirements are intended to reduce the number of parentheses necessary in Self code For example taking the minimum of two slots mand nand storing the result into a data slot i may be written as i m omin n Precedence Keyword messages have the lowest precedence For example i 5 factorial pi sine is interpreted as i 5 factorial pi sine 2 3 4 Implicit receiver messages Unary binary and keyword messages are frequently written without an explicit receiver Such messages use the current receiver self as the implied receiver The method lookup however begins at the current activation object rather than the current receiver see 2 1 4 for details on a
17. E m 0 LC tou 2 30 2 indicators and VM memory display des detu object memory code cache The indicators in the left part of the display correspond to various internal activities and events On the very left are the CPU bars which show how much CPU is used in various parts of the system The following table lists the individual indicators Table 5 The system monitor display indicators CPU Bar What It Means VM CPU time spent executing in the VM i e for primitives garbage col lection etc Lkup CPU time used by compile time and run time lookups Comp CPU time spent by the Self compilers The black part stands for time consumed by the non inling compiler NIC the gray part for the simple inlining compiler SIC Self CPU time spent executing compiled Self code The black part stands for time consumed by unoptimized NIC code the gray part for optimized SIC code CPU This bar displays the percentage of the CPU that the Self process is getting a completely filled bar equals 100 CPU utilization by Self Black stands for user time gray for system time Dot Below the CPU bar is a small dot which moves whenever a process switch takes place Indicator What It Means X compiling Y scavenge GC flushing compacting reclaiming sec reclaim ic flush LRU sweep page N N read write disk in out UNIX idle The X compiler where X is either nic or sic is compiling the method
18. R Real numbers may be written in decimal only The exponent of a floating point format number indicates multiplication of the mantissa by 10 raised to the exponent power i e nnnnEddd nnnn x 10 44 A number with a digit that is not appropriate for the base will cause a lexical error as will an integer constant that is too large to be represented If the absolute value of a real constant is too large or too small to be represented the value of the constant will be infinity or zero respectively Productions number gt Gnteger real integer gt base general digit general digit real fixed point float fixed point decimal decimal float gt decimal decimal e E 1 decimal general digit digit letter decimal gt digit digit base decimal r R Examples 123 16r27fe 1272 34e 15 1e10 10 Unlike Smalltalk integer literals are limited in range to smallInts 1 Tn situations where parsing the minus sign as part of the number would cause a parse error for example in the expression a 1 the minus is interpreted as a binary message a 1 20 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 2 4 7 Strings String constants are enclosed in single quotes With the exception of single quotes and escape sequences in troduced by a backslash VW all char
19. Scheme s let and let rec forms and more generally that a slot initializer may not refer to any textually enclosing object literal 2 2 Slot descriptors An object can have any number of slots Slots can contain data data slots or methods Some slots have special roles argument slots are filled in with the actual arguments during a message send 2 3 3 and parent slots specify inheritance relationships 2 3 8 A slot descriptor consists of an optional privacy specification followed by the slot name and an optional initializer 2 2 1 Read only slots A slot name followed by an equals sign and an expression represents a read only slot initialized to the result of evaluating the expression in the root context For example a constant point might be defined as parent traits point x 3 4 y 5 The resulting point contains three initialized read only slots 2 2 2 Read write slots There is no separate assignment operation in Self Instead assignments to data slots are message sends that invoke the assignment primitive For example a data slot x is assignable if and only if there is a slot in the same object with the same name appended with a colon in this case x containing the assignment primitive Therefore assigning 17 to slot x consists of sending the message x 17 Since this is indistinguishable from a message send that invokes a method clients do not need to know if x and x comprise data slo
20. Self There are three main parts of C glue e Calling functions e Reading assigning global variables e Reading assigning a component in a struct that is represented by a proxy object in Self In addition C glue for creating objects can be used to create C structs see section 5 13 9 The following sections describe each of these parts of C glue 8 13 6 Calling C functions The macro C_func_N where N is 0 1 2 is used to glue in a C function The number N denotes the number of arguments that should be given at the Self level when calling the function This number may be different from the number of arguments that the C function takes since e g some argument conversions see below produce two C arguments from one Self object Here is the general syntax for C_func_N C_func_N res_cnv res_aux fexp gfname fail_opt c0 a0 cN aN Compare this with the glue that was used in the encrypt example in section 5 13 4 C_func_2 string encrypt encrypt_glue string int The meaning of each argument to C_func_N is as follows e res_cnv res_aux these two arguments form a conversion pair that specifies how the result that the function returns is converted to a Self object In the encrypt example where the function returns a null terminated string res_cnv has the value string and res_aux is empty Table 3 lists all the possible values for the res_cnv res_aux pair e fexp is a C expression which evaluates to the
21. Self Handbook Documentation Release 2 for Self 4 4 isRectangular false an object lt 8 4type morph Modules morph morphoavine parent wags morph haseDrawOn alanvas El aCanvas FillArclithin baseBounds From Spanning 360 Color color self isRectangular le middlehouseDown evt tmp tmp color color otherColor otherColor tmp self otheriolor a pamieci rojen bari Mor ph State bling ow Figure 7 4 Figure 4 A new kind of morph has been created by modifying a copy of the standard morph The slots baseDrawOn isRectangular middleMouseDown and otherColor have been added to the morph to obtain the new behavior The morph itself appears on the left an outliner showing its slots appears on the right The new morph s input behavior can be customized by adding the method middleMouseDown vt tmp tmp color color otherColor otherColor tmp The morph now draws itself as a filled oval Clicking the middle mouse button on it causes its color to toggle between its original color and leaf green This new morph can used as a prototype any copies will get the state and behavior of the prototype at the time of copying However later changes to the prototype will not be reflected in the copies For example even if the prototype s middle mouse behavior were changed to cycle through three colors copies made before this change would still only toggle between two colors To allow the beh
22. a foreignFct object that represents the routine in the Self world Each of these steps is described in detail in the following sections 8 13 1 Proxy and fctProxy objects A foreign object is represented by a proxy object in the Self world A proxy object is an object that encapsulates a pointer to the foreign object it represents In addition to the pointer to the foreign object the proxy object contains a type seal A type seal is an immutable value that is assigned to the proxy object when it is created The type seal is intended to capture type information about the pointer encapsulated in the proxy For example proxies representing window objects should have a different type seal than proxies representing event objects By checking the type seal against an expected value whenever a proxy is opened many type errors can be caught The last property of proxy objects is that they can be dead or live If an attempt is made to use the pointer in a dead proxy object an error results deadProxyError Proxy objects may be explicitly killed by sending the primitive message _Ki11 to them Furthermore they are automatically killed after reading in a snapshot This way problems with dangling references to foreign objects that were not included in the snapshot are avoided FctProxy objects are similar to proxy objects they have a type seal and are either live or dead However they represent a foreign routine rather than a foreign object A fo
23. a parent argument slot named self For example a point addition method can be written as arg clone x x arg x y y arg y Il 4 In the user interface a read write slot is depicted as a single slot with a colon labelling the button used to access the value of the slot the assignment slot is not shown to save screen space In contrast a read only slot has an equals sign on the button 5 Nil is a predefined object provided by the implementation It is intended to indicate not a useful object 6 Although a block may be assigned to a slot at any time it is often not useful to do so evaluating the slot may result in an error because the activation record for the block s lexically enclosing scope will have returned see 2 1 7 10 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 point traits 2 2 Slot descriptors 11 Self Handbook Documentation Release 2 for Self 4 4 producing clone x x arg x y y arg y A slot name beginning with a colon indicates an argument slot The prefixed colon is not part of the slot name and is ignored when matching the name against a message Argument slots are always read only and no initializer may be specified for them As a syntactic convenience the argument name may also be written immediately after the slot name without the prefixed colon thereby implicitly declaring the argument slot Thus the follow
24. absent includesKey test if collection contains a given key Iterating do iterate passing each element to argument block doFirst Middle Last IfEmpty doFirst MiddleLast IfEmpty doFirstLast Middle IfEmpty doFirstMiddle Last IfEmpty reverseDo iterate with special behavior for first and last iterate with special behavior for first iterate with special behavior for ends iterate with special behavior for last iterate backwards through list with Do co iterate passing corresponding elements to block Reducing max return maximum element mean return mean of elements min return minimum element sum return sum of elements product return product of elements reduce With evaluate reduction block with elements reduceWith IfEmpty evaluate reduction block with elements evaluating block if empty Transforming 76 Chapter 6 Useful Selectors Self Handbook Documentation Release 2 for Self 4 4 asByteVector return a byte vector with same elements asString return a string with same elements asVector return a vector with same elements asList return a list with the same elements filterBy Into add elements that satisfy filter block to a collection mapBy add result of evaluating map block with each element to this collection mapBy Into add result of evaluating map block with each element to a collection Sorting sort sort receiver in place copySorted copy sorted in ascending order copyR
25. an icon consisting of two concentric circles The diagram on the right shows its submorph structure 82 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 A morph can be made a submorph of some other morph using the addMorph operation This operation updates both the owner slot of the submorph and the submorphs list of the owner to reflect the desired configuration For example adding morph B to morph A adds B to A submorph list removes B from its old owner if any and sets B s owner to A The addMorph operation also updates the layout of both B s old and new owners The global position of a morph is held invariant by addMorph although some morphs may perform an automatic layout as a side effect of addMorph immediately changing the position of the newly added morph A Y E lateliorph oa mi Button He i colocan Morph HH t rowlflorph soe worldS crollerMorph bd Figure 7 3 Figure 3 Using the core sampler to probe the submorphs at the point below its cross hairs The programming environment includes a tool called the core sampler available via the right button menu of any morph that can be used to explore the submorph structure of a composite morph The core sampler shows the set of submorphs below a given point the way a core sample of rock allows geologists to study the strata of rock at a given point The core sampler allows one to use the middle button me
26. and should be avoided l not identical Ordered lt less than gt greater than lt less than or equal gt greater than or equal three way comparison three way comparison with failure Numeric operations 1 absolute Value inverse negate ceil floor truncate round asFloat asInteger double quadruple half quarter min max mean pred predecessor succ successor power log square add subtract multiply divide divide exactly returns float divide and round to integer tends to round up divide and round up to integer divide and round down to integer modulus absolute value multiplicative inverse additive inverse round towards positive infinity round towards negative infinity truncate towards zero round coerce to float coerce to integer multiply by two multiply by four divide by two divide by four minimum of receiver and argument maximum of receiver and argument mean of receiver and argument predecessor predecessor successor successor raise receiver to integer power logarithm of argument base receiver rounded down to integer square Continued on next page 10 5 Useful Selectors 139 Self Handbook Documentation Release 2 for Self 4 4 Table 10 1 continued from previous page squareRoot factorial fibonacci sign even odd Bitwise operations integers square root factorial fibonacci signum 1 0 1 true if receiver
27. and trace if an error is encountered while trying to handle an error 8 5 An example Here is an expression that produces an error in the current system 110 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 Self 7 100000 factorial The stack has grown too big Self limits stack sizes and cannot resume processes with stack overflows To debug type attach or to show stack type zombies first printError The error arose because the recursive method factorial exceeded the size allocated for the process stack which resulted in a stack overflow The virtual machine currently allocates a fixed size stack to each process and does not extend the stack on demand 8 6 Lookup errors Lookup errors occur when an object does not understand a message that is sent to it How the actual message lookup 1s done is described in the Language Reference Manual No foo slot found in shell lt 0 gt The lookup found no slot matching the selector foo More than one system slot was found in shell lt 0 gt The matching slots are oddballs lt 6 gt and prototypes lt 7 gt The lookup found two matching system slots which means the message is ambiguous The error message also says where the matching slots were found Ambiguities can often be re solved by changing parent priorities No fish delegatee slot was found in lt a child of lobby gt lt 12 gt The lookup f
28. another editor will select that one as the typing focus and to indicate that it is no longer the focus this editor s background will change to match the outliner The white triangle in the lower right corner of the editor which can barely be seen in the printout of this document can be dragged to resize the editor Someone has done a poor job of indenting this method so fix it by clicking to the left of the capital I and deleting two spaces The red and green buttons that just appeared indicate the text has been changed it no longer reflects the source code of the real method Hitting the red button will cancel the changes while hitting the green button will accept them and 48 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4 anExampleO bject Aj El x Module programming amples parent traits clonable anUncategorized Constant 3 14159 anUncategonzed Method user Query report Hello there El anUncategonzed Vanable 17 34 4 a category of slots aCategorizedConstant 3 14159 aCategonzedMethod user Query report Hello there El aCategonzed Variable 17 3 4a subcategory whoAml w E os environmentAt LOGNAME 4 anExampleO bject Aj Ej x Module programmingBbamples parent traits clonable anUncategonzed Constant 3 14159 anUncategonzed Method user Query report Hello there El anUncategonzed Vanable 17 3 4a category of slots aCategonzedConstant 3 14159
29. as which the module in which to record information about the object as a whole such as the object comment In a few seconds if outliner updating is on the outliner titles of the ovalMorph prototype and its traits object will be updated to show the new names for these objects To allow a composite morph containing ovalMorphs to be saved in a file the prototype method in the prototype not the traits must return the prototype ovalMorph The ovalMorph prototype already has a prototype method that was copied from the original morph prototype Change the body of the prototype method in the filing out category to ovalMorph Many Smalltalk programming environments allow an instance variable to be added to a class at runtime The new instance variable is propagated down to all subclasses and added to all existing instances of the class and its subclasses with an initial value of nil The Morphic programming environment can provide a similar service for the copied down slots of prototypes with two significant differences 1 changes to the values of a copied down slots are propagated as well as slot additions and removals and 2 changes are propagated only to objects registered in the global namespace 88 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 4 globals 4 traits 117 Modules 106 Modules bapylications slots wags slows boollectsons bapplications beraphis bco
30. button and that method called evnironmentAt IfFail because we just sabotaged it Of course there is no such method but Self creates one dynamically to handle the error The little boxes represent the receiver and arguments of the methods on the stack Get the receiver of the evnironment message Click on the box to the left of the word evnironmentVariable the one labelled bal os if you are running on the Macintosh 5 If you examine the slot s annotation available via the slot menu it will show that the system has guessed that the new slot named me should be saved in the programmingExamples module and that instead of saving its actual contents the slot should just be initialized to the string Gumby 6 Since the Self compiler inlines calls automatically Self code tends to be written in a highly factored deeply nested style Thus the debugger filters out stack frames that seem to be unimportant If it ever filters out the frame you need to see there is a Don t filter frames entry in the stack s middle button menu 52 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4anExampleObject Ay Y Module programming amples parent traits clonable anUncategorized Constant 3 14159 anUncategorizedMethod user Query report Hello there 8 anUncategonzed Variable 17 3 4 2 category of slots 3 14159 aCategorizedMethod user Query report
31. contains a unixFile like object 8 13 Interfacing with other languages 129 Self Handbook Documentation Release 2 for Self 4 4 capitalize stdio Figure 8 4 Figure 6 A Self process and how it fits into a pipe line that represents the socket connection When the forked process terminates the socket connection is shut down The tosel f UNIX process then terminates The Self expression that forms the Self process is specified on the command line when toself is started For example 1f the server has been started the following can be typed at the UNIX prompt proto toself stdio writeLine 5 factorial printString 120 proto echo something toself capitalize stdio SOMETHING proto toself capitalize stdio Write some text that goes to stdin of the toself program WRITE SOME TEXT THAT GOES TO STDIN OF THE TOSelf PROGRAM More text MORE TEXT D proto If you want to try out these examples locate the files server self socks so and toself The path name of the file so cks so is hardwired in the file server sel1f so please make sure that it has been set correctly for your system Then file in the world and type server start fork at the Self prompt Now you can go back to the UNIX prompt and try out the examples shown above 8 13 17 Outline of toself toself is a small C program found in the file toself c It operates in the three phases outlined above 1 Try to con
32. does not discuss the objects used to implement system facilities for example there is no discussion of the objects used to implement the graphical user interface nor does 1t discuss how to use programming support objects such as the command history object such tools are described in The Self User s Manual The reader is assumed to be acquainted with the Self language the use of multiple inheritance the use of traits objects and prototype objects and the organizing principles of the Self world as discussed in UCC91 3 1 World Organization 3 1 1 The Lobby The lobby object is thus named because it is where objects enter the Self world For example when a script that creates a new object is read into the system all expressions in that script are evaluated in the context of the lobby That is the lobby is the receiver of all messages sent to self by expressions in the script To refer to some existing object in a script the object must be accessible by sending a message to the lobby For example the expression _AddSlots newObject ntries lt list copy requires that the message 1 ist be understood by the lobby the implicit receiver of the message so that the ent ries slot of the new object can be initialized The lobby slots traits globals and mixins are the roots of the object namespaces accessible from the lobby The organization of these namespaces is described in the next section The slot lobby a
33. function that is being glued in In the simplest case such as in the encrypt example the expression is the name of a function but in general it may be any C expression involving function pointers etc which in a global context evaluates to a function e gfname the name of the function which the C_func_N macro expands into In the encrypt example the convention of appending _glue to the C function s name was used When accessing a glued in function from Self the value of gfname is the name that must be used e fail_opt there are two possible values for this argument It can be empty as in the example or it can be fail In the latter case the C function being called is passed an additional argument that will be the last argument and have type void x Using this argument the C function may abort its execution and raise an exception The result is that the IfFail block in Self will be invoked e ci ai each of these pairs describes how to convert a Self level argument to one or more C level arguments For example in the glue for encrypt c0 a0 specifies that the first argument to encrypt is a string Likewise c1 al specifies that the second argument is an integer Note that in both these cases the a part of the conversion is empty Table 3 lists all the possible values for the ci ai pair Handling failures Here is a slight modification of the encryption example to illustrate how the C function ca
34. gt Al EI x Copydown parent morph beers aS Copydown selector copyRemoveAlMorphs Complete Yes No Slots to omit parent prototype rawBox rawColor Copydown parent Modules morphLib morphsa ving Copydown selector parent traits circleMorph Slots to omit center apomi0e 0 Modules morph morphSaving radius 50 3 parent traits morph rawColor a paintileaf 4 Basic Morph State 4 Basic Morph State hResizing 0 hResizing 0 vResizing 0 vResizing 0 velcroF lag rue 3 velcroFlag vue 3 cachedMinHeight nil 3 cachedMinHeight ml 3 cachedMinWidth nil 3 cachedMin Width nil 3 layoutOkay false 3 layoutOkay false noStickOuts false 3 noStickOuts false 3 TawBox a rectangle 0 0 100080 rawMorphs vector 3 rawColor a paintithala rawOwner mil i rawMorphs vector 3 4 filing out rawOwner nil 3 prototype circleMorph E A filing out prototype morph 8 5 4 The Transporter 71 Self Handbook Documentation Release 2 for Self 4 4 The Basic Morph State category of slots has been copied from those in morph by first copying the morph and removing all its submorphs i e by sending it copyRemoveAllMorphs and then copying the resultant slots omitting parent prototype rawBox and rawColor The first three of these slots were omitted because their contents had to be different copied down slots are copied they cannot be specially initialized in Self 4 1 The omitted slot rawBox is more interesting circle morphs
35. if receiver is true ifFalse evaluate argument if receiver is false ifTrue False ifFalse True evaluate first arg if true second arg if false evaluate first arg if false second arg if true Local exiting exit exitValue exit block and return nil if block s argument is evaluated exit block and return a value if block s argument is evaluated Basic looping loop loopExit loopExitValue repeat the block forever repeat the block until argument is evaluated then exit and return nil repeat the block until argument is evaluated then exit and return a value Pre test looping whileTrue whileFalse whileTrue whileFalse repeat the receiver until it evaluates to true repeat the receiver until it evaluates to false repeat the receiver and argument until receiver evaluates to true repeat the receiver and argument until receiver evaluates to false Post test looping until True repeat the receiver and argument until argument evaluates to true untilFalse repeat the receiver and argument until argument evaluates to false Iterators do iterate passing each element to the argument block to By Do iterate with stepping to Do iterate forward upTo By Do iterate forward without last element with stepping upTo Do iterate forward without last element downTo By Do reverse iterate with stepping downTo Do reverse iterate Collections Sizing isEmpty test size if collecti
36. language is actually not a single language but one for each supported foreign language Presently C and C are supported Section 5 13 5 describes C glue and section 5 13 9 describes C glue 8 13 3 Compiling and linking glue code Since glue code is a special form of C code a C compiler is needed to translate it The way this is done may de pend on the computer system and the available C compiler The following description applies to Sun SPARCstations using the GNU g compiler A specific example of how to compile glue code can be found in the directory containing the toself demo see section 5 13 16 for further details The makefile in that directory describes how to translate a c file containing glue into something that can be invoked from Self This is a two stage process first the c file is compiled into a o file which is then linked perhaps with other o files and libraries that the glue code depends on f into a so file a so called dynamic library While the compilation is straightforward several issues concerning the linking must be explained Linking Before a foreign routine can be called it must be linked to the Self virtual machine The linking can be done either statically i e before Self is started or dynamically i e while Self is running The Self system employs both dynamic and static linking but users should only use dynamic linking as static linking requires more understanding of the structure of the Virt
37. named Y into machine code The Self object memory is being scavenged A scavenge is a fast partial garbage collection see Ung84 Ung86 Lee88 The Self object memory is being fully garbage collected Self is flushing the code cache Self is compacting the code cache Self is reclalming space in the code cache to make room for a new method Self is flushing some methods in the code cache because there is not enough room in one of the secondary caches the caches holding the debugging and dependency information Self is flushing all inline caches Self is examining methods in the code cache to determine whether they have been used recently page faults occurred during the last time interval N is not displayed if N 1 The time interval currently is 1 25 of a second Self is blocked reading from a slow device e g the keyboard or mouse Self is blocked writing to a slow device e g the screen Self is doing disk I O Self is blocked in some UNIX system call other than read or write Self has nothing to do shows up only when using processes 10 7 The system monitor 147 Self Handbook Documentation Release 2 for Self 4 4 The middle part of the display contains some information on VM memory usage displayed in textual form as described below Table 6 VM memory status information Name Description RSRC Size and utilization of the resource area an area of memory used for temporar
38. ow ao erences Find slot moral D Expand All Collapse All Evaluator 4ovalMorph type ovalMorph traits ovalMorp Of which slots Modules morph morphSaving Modules ovall e parent ars ovaio ph parent otherColor a painte35 gt lea baseDrawOn at ovalModule basic Mor ph State isRectanqular jose ing aw middleMouseDown ewt E morgphTypeMame ovale ph 4ovalMorph type ovalMorph traits ovalMoiTo which module Modules morph morphSaving Modules ovi a parent waits ovalkMor ph parent ovalliodule otherColor a paim lt 35 ieaf baseDrawOn other K basic Mor ph State isRectangular false bingo middleMouseDown ewt a morphTypeName ovalior ph Figure 7 12 Figure 12 Assigning all the slots of the new traits object to the new module 7 3 Morph Traits and Prototypes 93 Self Handbook Documentation Release 2 for Self 4 4 4 Changed Modules Y morph W morph3aving W ovalModule 4ovalMorphi type ovalMorph 4traits oval Morph Module ovalbModule Module ov altiodule parent was orior ph parent aes morph otherColor a painte35 gt fleaf baseDrawOn aCanvas F basi Morph State ishectangular jae bing or middleMouseDown evt g morphTypeName oraikior ph 4 Changed Modules w moarnh W m Filing out module oval Module ar k 4ovalMorph type ovalMorph traits oval Morph Module ovaltvic dule Module ovalo dule parent ass ovalkor ph parent Wags mor pa otherColor a
39. pomrc35 gt leaf baseDrawOn alanvas E basic Mor ph State isRectangqular AS bling ow middlehiouseDown evt I morphTypeName ovaikior ph Figure 7 13 Figure 13 Saving the code for the new morph in a module file 94 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 6 Assign all slots of the new traits and prototype objects to ovalModule 7 Start programming the new behavior This procedure does all the housekeeping chores up front so the module can be filed out at any time As the program mer works the system will deduce that any slots added to ovalMorph s traits or prototype should be placed in the same module as the other slots in that object ovalModule In a future release of the system the initial housekeeping may be automated This would make creating a new kind of morph a one step operation 7 4 Saving a Composite Morph The system includes an experimental facility for store the structure of a composite morph to a file This allows a morph constructed by direct manipulation to be saved into a file that can be read later to reconstruct the morph This is how the factory was created The morph saving facility requires that every morph and submorph to be saved supply implementations of the messages slotsToNotFileOut appendOtherSlotsOnto storeStringNeeds and prototype Unfortunately because morph saving was added later as an experiment not all mor
40. slot through which resend was delegated was not found first argument to the _Perform primitive was not a canonical string number of args supplied to _Perform primitive does not match selector the named primitive failed with given error string Other system triggered messages postRead slot to evaluate after reading a snapshot 79 Self Handbook Documentation Release 2 for Self 4 4 80 Chapter 6 Useful Selectors CHAPTER SEVEN MORPHIC THE SELF USER INTERFACE FRAMEWORK 7 1 Overview Morphic is a user interface framework that supports composable graphical objects along with the machinery required to display and animate these objects handle user inputs and manage underlying system resources such as X displays fonts and color maps A primary goal of morphic is to make it easy to construct and edit interactive graphical objects both by direct manipulation and from within programs A Morphic window shows just one portion of a large two dimensional world The window can be panned around in this world allowing different areas to be used for different activities Multiple users can be active in this world simultaneously working either in the same area for collaborative work or in disjoint areas for independent work Every user can see the screen boundaries cursors and actions of the other users The sharing is implemented via the X protocol so the other users can be physically remote as long as there is s
41. smallInt overflowError unsigned_int unsigned int smallInt overflowError long long smallInt overflowError signed_long signed long smallInt overflowError unsigned_long unsigned long smallInt overflowError smi smi smallInt overflowError int_or_errno n int int a UNIX error 1 float float float 2 double double float 2 long_double long double float 2 string char byte vector nullPointerError 3 proxy ptr_type ptr_type proxy nullPointerError 3 4 8 type_seal proxy_null ptr_type ptr_type proxy 4 8 type_seal proxy_or_ermo ptr_type ptr_type proxy a UNIX error 4 5 8 type_seal n fct_proxy ptr_type ptr_type fctProxy nullPointerError 3 6 8 type_seal arg_count fct_proxy_null ptr_type ptr_type fctProxy 6 8 type_seal arg_count oop oop corresponding 7 8 object 1 This conversion returns an integer value unless the integer has the value n the second part of the conversion often 1 If the integer is n the conversion interprets the return value as a UNIX error indicator It then constructs a string describing the error by looking at errno and invokes the IfFail block with this string Precision may be lost This conversion fails with nul1PointerError if attempting to convert a NULL pointer The pt r_type is the C C type of the pointer The type_seal is an expression of type intor char The conversion constructs a new proxy object stores the C C pointer in it and sets its type seal to be the value of typ
42. the C C value corresponding to the given Self object 124 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 Table 3 Argument conversions from Self to C C Conversion Second part Self type C C type Errors Notes bool boolean int 0 or 1 badTypeError char smallInt char badTypeError over 1 flowError signed_char smallInt signed char badTypeError over flowError unsigned_char smallInt unsigned char badSignError bad TypeError overflow Error short smallInt short badTypeError over flowError signed_short smallInt signed short badTypeError over flowError unsigned_short smallInt unsigned badSignError bad short TypeError overflow Error int smallInt int badTypeError signed_int smallInt signed int badTypeError unsigned_int smallInt unsigned int badSignError bad TypeError long smallInt long badTypeError signed_long smallInt signed long badTypeError unsigned_long smallInt unsigned long badSignError smi smallInt smi badTypeError 2 unsigned_smi smallInt smi badSignError bad 2 TypeError 8 13 Interfacing with other languages 125 Self Handbook Documentation Release 2 for Self 4 4 Conversion Second part Self type C C type Errors Notes float float float badTypeError 3 double float double badTypeError 3 long_double float long double badTypeError 3 bv ptr_type byte vector ptr_type badTypeError 4 bv_len ptr_type byte vector ptr_type int badSi
43. traits clonable anUncategonzed Constant 3 14159 anUncategonzed Method user Query report Hello there El anUncategonzed Vanable 17 4a category of slots aCategonzedConstant 3 14159 aCategorizedMethod user Query report Hello there B aCategorzed Variable 17 3 me Gumby 4a subcategory whoAml A os environmentAt LOGNAME IfFail The Phantom whoAmI Getit Doit Close 4a subcategory who Am a os evnironmentAt LOGNAME IfFail The Phantom whoAmI Getit Doit Close 58 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4a subcategory whoAml B os evrilironmentAt LOGNAME IfFail The Phantom whoAmI 4 Process whoAml a Lookup enor evnironmentAtlfFail not found o Ge Continue Step Step lexical Next Finish Frame Abort pStack 4 Process whoAm Lookup enor evnironmentAtlfFal not found Continue Step Step lexical Next Finish Frame Abort 4Stack balsgs evmironmentAt arg LOGNAME IfFail arg tom B eCbjiect whoAml B 2Object whoAm 8 Less stack gt macOSGlobals os E x 5 2 Browsing Concepts 59 Self Handbook Documentation Release 2 for Self 4 4 This object represents the interface to the Macintosh operating system The little button with the apostrophe in the top left hand corner indicates that this object has a comment Push the button to show or hide the comment gt macOSGlob
44. underscore _ and calls the corresponding primitive operation Primitives are predefined functions provided by the implementation A normal send does a lookup to obtain the target slot if the lookup was successful the slot is subsequently evaluated If the slot contains a data object then the data object is simply returned If the slot contains the assignment primitive the argument of the message is stored in the corresponding data slot Finally if the slot contains a method an activation is created and run as described in 2 1 6 If the lookup fails the lookup error is handled in an implementation defined manner typically a message indicating the type of error is sent to the object which could not handle the message The function send rec sel args is defined as follows 2 General delegation for explicit receiver messages is supported through primitives in the implementation see Appendix 9 8 16 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 Input rec the receiver of the message sel the message selector args the actual arguments Output res the result object Algorithm if begins_with_underscore sel then invoke_primitive rec sel args primitive call else M lookup rec sel do the lookup case M 0 error message not understood M 1 res eval rec M args see 2 1 M gt 1 error ambiguous message send end end return res
45. unique it is only necessary to have one of them in the system It may even be important that the system contain exactly one of some kind of object Objects playing the role of unique objects are called oddballs Because there is no need to share the behavior of an oddball among many instances there is no need for an oddball to have separate traits and prototype objects Many oddballs inherit a copy method from traits oddbal11 that returns the object itself rather than a new copy and most oddballs inherit the global namespace and default behavior from the lobby 4 2 3 Inline Objects An inline object is an object that is nested in the code of a method object The inline object is usually intended for localized use within a program For example in a finite state machine implementation the state of the machine might be encoded in a selector that would be sent to an inline object to select the behavior for the next state transition state sendTo inComment c c ifTrue state inCode self inCode c c jifTrue state inComment False 40 Chapter 4 A Guide to Programming Style Self Handbook Documentation Release 2 for Self 4 4 1 With nextChar In this case the inline object is playing the role of a case statement Another use of inline objects is to return multiple values from a method as discussed in section 4 4 Yet another use of inline objects is to parameterize the behavio
46. world To do this ask Self to read expressions from a file VM all2 self _RunScript Various configurations are possible al 12 is the released system sma11UI2 is the same but without the various example applications and all contains the old release 3 0 experimental user interface Unless you have asked Self not to print script names you should see something like reading all2 self reading init self 4 After all the files have been read in Self will start the process scheduler initialize its module cache and print 3 13 How to build the world 35 Self Handbook Documentation Release 2 for Self 4 4 self 0 That last line is the Self prompt indicating that the system is ready to read and evaluate expressions 3 14 How to use the low level interrupt facilities There are two low level ways to interrupt a running Self program Control C and Control The second way works even if the Self process scheduler is not running In response to the interrupt you will see one of two things If the Self scheduler is not running you will be returned directly to the VM prompt If the scheduler is running you will be presented with a list of Self processes the process menu Self 9 gt 100000 100000 do AG Interrupt Ready lt 25 gt scheduling process 100000 100000 do Select a process or q to quit scheduler 25 Select lt return gt for no action p to print the stack k to kill the pro
47. ypt_g pp e An empty argument signifying that encrypt is not to be passed a failure handle explained later e string specifies that the first argument to encrypt is a string es e int specifies that the second argument to encrypt is an int Having written this file we now prepare a makefile to compile and link it To do this we can extend the makefile in objects glue sun4 svr4 depending on OS in use and then run make This results in the shared library file encrypt so Finally to try it out we can type these commands at the Self prompt or in the UI gt _AddSlotsIfAbsent encrypt lobby gt encrypt foreignFct copyName encrypt_glue lobby gt encrypt lt C function encrypt_glue gt gt encrypt value Hello Self With 3 Khoor Vhoi gt encrypt value Khoor Vhoi With 3 Hello Self Path encrypt so Comparing the signature for the function encrypt with the arguments to the C_func_2 macro it is clear that there is a straightforward mapping between the two One day we hope to find the time to write a Self program that can parse a C or C header file and generate glue code corresponding to the definitions in it In the meantime glue code must be handwritten 8 13 Interfacing with other languages 119 Self Handbook Documentation Release 2 for Self 4 4 8 13 5 C glue C glue supports accessing C functions and data from
48. 14 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 0 integers 0 integer parent 0 0 floats 0 0 float parent E CI strings string parent SS jo so blocks block parent lobby value With block method Figure 8 2 Figure 4 The initial Self world part 2 8 11 The initial Self world 115 Self Handbook Documentation Release 2 for Self 4 4 All of the prototypical mirrors consist of one slot a parent slot named parent Each of these parent slots points to an empty object denoted in Figure 5 by smiMirror Prototypical mirror on a small integer the reflectee is 0 floatMirror Prototypical mirror on a float the reflectee is 0 0 string Mirror Prototypical mirror on a canonical string the reflectee is the empty canonical string processMirror Prototypical mirror on a process the reflectee is the initial process byte VectorMirror Prototypical mirror on a byte vector the reflectee is the prototypical byte vector objVectorMirror Prototypical mirror on object vectors the reflectee is the prototypical object vector assignmentMirror Mirror on the assignment primitive the actual reflectee is an empty object mirrorMirror Prototypical mirror on a mirror the reflectee is slotsMirror slotsMirror Prototypical mirror on a plain object without code the reflectee is an empty object blockMirror Prototypical mirror
49. 60 Width 3 Color color self The oval is drawn with a pen three pixels wide To accommodate the extra width the rectangle passed to the canvas is indented by three pixels Note A morph should never draw outside its baseBounds When this method is accepted all copies of the prototype reflect the change However Morphic doesn t automatically redraw instances when the draw method is changed To see the change drag some large object over the ovals to make them redraw At this point the prototype for a new kind of morph has been created and the behavior common to all its instances has been factored into a separate traits object to facilitate later changes The next step is to install the prototype and its traits in the global and traits namespace objects Doing this allows the morph prototype and its traits to be referred to by name 7 3 Morph Traits and Prototypes 87 Self Handbook Documentation Release 2 for Self 4 4 4an object lt 8 type morph 4an object lt 370 gt Modules morph morphSaving Module parent anobpct lt 370 gt parent wats mor ph otherColor a pami lt 357 gt leaf baseDrawOn aCanvas Ne b Basic Mor ph State aCanvas arcWithin baseBounds indent 3 b fling Re From 0 Spanning 360 Color color self isRectangular false middleMouseDown evt a Figure 7 7 Figure 7 Changing the shared traits object changes the behavior of copies of the prototype instances In this case the draw metho
50. 854 24556 245624494 ebb bS5 4 BAS HS 7 11 Some Useful Morphs iso ia eA A eS ad OS a Soe 712 The Graphical Environment e s e na ee ee a a Oa e a ea ee a ee a E Virtual Machine Reference Sl Startup Options acp e 24a Seward GRAN SG EYE SERS SOA Ae RO ee 8 2 System trigpered Messages some 5H Ges See ee eR RY Skee BEEP Ree ee es 8 3 Run timemessage lookup Errors 22 see en Se ae AA BS BAS Gyles OE w Bees 8 4 Low level error messages sac ts EG RRR na RE Ee RE 8 9 Ame xample o 2 be 4 86 849 6445 bo eH hd e EOS Ee Ee Ee Rew 6 Lookupemors 2 5 564 4 224445 4 6 Be ES Reh Bb eS OS a amp ae E 8 7 Programmer defined errors lt coo oo ks ee a AREER A ee eG 8 8 UPQIMIVE SHOTS as Ge RR AS DAS RAD A SLES Sees dk Ges 8 9 Nonrecoverable process errors 2 04 5 o ee a A ee ee bee a SO Fatal errors e ee se aos E uaia a eS A a a SE ae Gee Dw dy SO 8 11 The initial Self World 0 04 443 a ee ee ala Seba See Be eee lt Soa Y 312 Ophion Primitives e bae ot ded tee Bh Sed dite e daa 8 13 Interfacing with other languages s s poe s 48 as we ERS ee PER E SRO References 10 Appendices TO CAOS tes EE GA EEE OER EEE EEA COE HS OO eee Se he we 4 10 2 LEXICANOVSIVIEW 2 Ss Bide eb eee eb Bhi eet ede Shee EPS 10 3 SVMLAXOVERVIEW u e e Ree e ACA sets ein ae BB ee ee e ee a ee a 104 Bulteitypes poso x dite ged e Ae GoGo al dine et Ad a Bice cg 10 5 Glossary of Usetul Sel ctors oie oros peca ee eee ee Re 10 6 Every Menu
51. Color a pant lt 357 gt leafl b Basic Mor ph State p fling ov parent traits morph Evaluate Dismiss Figure 7 5 Figure 5 A new traits object has been created to hold behavior to be shared by all instances of the morph Arrow dragging is being used to make the parent slot of the new morph point to the new traits object Now the behavior to be shared can be moved from the prototype into the new traits object Invoke the Move command on the middle button menu for the isRectangular slot This causes the slot to be plucked out of the object Drop the slot onto the shared traits object This causes it to be added to the that object Repeat this process for the baseDrawOn and middleMouseDown slots 86 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 The Self language uses slot inheritance to share both data isRectangular and behavior baseDrawOn and mid dleMouseDown The programming environment supports a similar kind of uniformity by allowing any slot to be moved or copied by via drag and drop A entire category can also be copied or moved by dragging Note that when moving a slot between an object and its parent there is an interval during which the slot is not in either object If a message matching the slot name is sent to the object during this interval the object s response is be determined by a slot inherited from a parent higher in the inheritance chain
52. Item in the Programming Environment e 10 7 Thesystem Monitor ssis ga eh ra ee e Be HS a eee i 10 8 Primitives eese ER eR A A oe eRe PERE baa AA 101 102 104 105 109 109 109 109 110 110 111 111 111 112 112 112 116 117 133 Self Handbook Documentation Release 2 for Self 4 4 Release 2 for Self 4 4 Date August 02 2011 Edited by Russell Allen Authors in alphabetical order Ole Agesen Lars Bak Craig Chambers Bay Wei Chang Urs H lzle John Maloney Randall B Smith David Ungar and Mario Wolczko Thanks to Ganesh R for his transcription services CONTENTS 1 Self Handbook Documentation Release 2 for Self 4 4 2 CONTENTS CHAPTER ONE INTRODUCTION Self is a prototype based dynamic object oriented programming language environment and virtual machine centered around the principles of simplicity uniformity concreteness and liveness Self includes a programming language a collection of objects defined in the Self language and a programming environment built in Self for writing Self programs The language and environment attempt to present objects to the programmer and user in as direct and physical a way as possible The system uses the prototype based style of object construction The first version of the Self language was designed in 1986 by David Ungar and Randall B Smith at Xerox PARC A series of Self implementations and a graphical programming environment were b
53. Self Handbook Documentation Release 2 for Self 4 4 Russell Allen Ed August 02 2011 CONTENTS Introduction 3 LE System Overview Los e rc A A eS e a 3 Language Reference 5 21 Objects o ocro oponer rs a A ee we Ea 5 22 Slot dESCTIP OTS e sa s rd A RR amp Gee Sw ad a S 9 23 EXPLOSION A A A A a 13 ZA Lexical elements cata a RA A a Boe A a E 19 The Self World 23 3 1 World Organization lt 6 25 cee eee OE ew ES Ae eG See ee Ap 23 32 The Roots of Behavior amp 44 4 6 S24 oo eRe Gee oh oe die oh Bt Oe ee ee ee ae A ees 24 3 3 Blocks Booleans and Control Structures 5 2 44 5554 0 bea Rebbe bad eee ee ee eS 25 34 Numbers and Time rs escusa ee A eee ea ELA ead 27 3 3 Collections gt sas e eh ri e a A ey ak o aa ce I ay a a 28 36 Pals criar Oe ae a Be eR ae Bee a GS ee Se al Go ea 31 Soh MIOR oee a e hols kG a hd eee A BR oh a Ba GB RE ae ate R 32 338 Messag a oi cba oe BAe ee eee heed a we AO ed ha ed 32 3 9 Processes and the Prompt sx sobo eA A eo eR a a a a i 33 S10 Force mODbJEC S ua eA Ae ee EA ee a Ree Se EW eo ee a Ree 33 SALE OO UNE he DAS A he A Sree wos Gre Behe 34 312 OMe r OBEC c 6 5 42 dor ta a a a o add a de ds 34 34 35 How to build the world s s s s moe i p ke e iE o ido babe o N 35 3 14 How to use the low level interrupt facilities o oo e 36 3 15 Using the textual debupper oce e nack e ee a ee a Ge ee a a ee 37 A Guide to Programming Style 39 4 1 Behaviorism versus Reflection 2
54. This slot initially contains nil This object contains slots containing the general system objects includ ing nil true false and the prototypical vectors and mirrors Objects in systemObjects nil true false vector byte Vector proxy fctProxy vector parent byte Vector parent slotAnnotation objectAnnotation profiler mirrors The initializer for slots that are not explicitly initialized Indicates not a useful object Boolean true Argument to and returned by some primitives Boolean false Argument to and returned by some primitives The prototype for normal vectors The prototype for byte vectors The prototype for proxy objects The prototype for fctProxy objects The object that vector inherits from Since all object vectors will inherit from this object because they are cloned from vector this object will be the repository for shared behavior a traits object for vectors Similar to vector parent the byteVector traits object The default slot annotation object The default object annotation object The prototype for profilers See below Literals and their parents integers O parent floats 0 0 parent canonical strings parent blocks parent Integers have one slot a parent slot called parent All integers have the same parent see 0 parent below All integers share this parent the integer traits object Floats have one slot a parent slot called parent Al
55. a value when the method is invoked Message lookup is the process by which objects determine how to respond to a message which slot to evaluate by searching objects for slots matching the message Inheritance is the mechanism by which message lookup searches objects for slots when the receiver s slots are exhausted An object s parent slots contain objects that it inherits from Dynamic inheritance is the modification of object behavior by setting an assignable parent slot A resend allows a method to invoke the method that the first method the one that invokes the resend is over riding A directed resend constrains the lookup to search a single parent slot Cloning is the primitive operation returning an exact shallow copy a clone of an object i e a new object containing exactly the same slots and code as the original object A prototype is an object that is used as a template from which new objects are cloned A traits object is a parent object containing shared behavior playing a role somewhat similar to a class in a class based system Any Self implementation is required to provide traits objects for integers floats strings and blocks i e one object which is the parent of all integers another object for floats etc The root context is the object that provides the context i e set of bindings in which slot initializers are evalu ated This object is known as the lobby During slot initialization self is bound to t
56. acters including formatting characters like newline and carriage return lying between the delimiting single quotes are included in the string To allow single quotes to appear in a string and to allow non printing control characters in a string to be indicated more visibly Self provides C like escape sequences t tab b backspace n newline f form feed r carriage return v vertical tab a alert bell YO null character backslash single quote Y double quote question mark A backslash followed by an x d or o specifies the character with the corresponding numeric encoding in the ASCII character set xnn hexadecimal escape dnnn decimal escape onnn octal escape There must be exactly two hexadecimal digits for hexadecimal character escapes and exactly three digits for decimal and octal character escapes legal hexadecimal decimal and octal numbers as well as character escapes specifying ASCII values greater than 255 will cause a lexical error For example the following characters all denote the carriage return character ASCII code 13 r xOd d013 10015 A long string may be broken into multiple lines by preceding each newline with a backslash Such escaped newlines are ignored during formation of the string constant A backslash followed by any other character than those listed above will c
57. allow us to merge changes to the same program we decided to represent its pieces as Unix source files amenable to RCS The Self Transporter was built to save programs as source files 5 4 4 Objects vs Slots But what is a program Although a new program frequently involves creating new objects it also can mean added slots to existing objects For example a program to find palindromes might add a slot to traits string called 68 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 isPalindrome So we decided to refine the granularity of the Transporter to the slot level each slot has an anno tation its module which gives the name of the source file containing that slot This hair or rather object splitting implies that one object may be built incrementally as the result of reading several files and so the transporter endeavors to keep the order that the files are read in as independent as possible Since each object can possess slots in different modules the outliner shows a summary of the modules of an object sorted by frequency Turned around a module can be viewed as a collection of slots plus some other information each module also includes a directory a list of submodules to be read in whenever it is read and post FilelIn method to be run whenever the module is read These data allow modules to be organized hierarchically by subsystem for example the allUI2 module includes all the modules
58. als os Aj amp x his object provides low level access to selected Mac cal Many Mac calls are provided through the indirect system c files sockets are opened closed using specific direct pr that the virtual machine can keep track of open files ne the select call A little philosophy at the unix os level every operat takes a failure block to give the user the ability to har failures The block gets one argument a string with the To automatically resize the outliner to show all the text press control L To see one of Self s scroll bars grab the comment s resize triangle with the left button and move it up a bit gt macOSGlobals os AJE xf This object provides low level access to selected Mac c Many Mac calls are provided through the indirect syster files sockets are opened closed using specific direct that the virtual machine can keep track of open files the select call A little philosophy at the unix os level every oper takes a failure block to qive the user the ability to 1 The affordance that appears on the right of the text is the scroll bar and you can either drag on the little black line or just click in the bar to scroll the text up or down Push the little apostrophe button again to hide the comment Now you could expand this object to find the correct spelling of the evnironment message But instead pretend that all you remember is that it has the word Variable in 1t somewhe
59. also used as an argument to new process creation you can create a new process to execute the message by sending it fork Modules sending message selector interceptor 3 9 Processes and the Prompt Self processes are managed by a simple preemptive round robin scheduler Processes can be stepped suspended resumed terminated or put to sleep for a specified amount of time Also the stack of a suspended process can be examined and the CPU use of a process can be determined A process can be created by sending fork to a message The prompt object takes input from stdin and spawns a process to evaluate the message Input to the prompt is kept in a history list so that past input can be replayed similar to the history mechanism in many Unix shells Modules process scheduler semaphore prompt history 3 10 Foreign Objects clonable proxy fctProxy foreignFct foreignCode The low level aspects of interfacing with code written in other languages via C or C glue code are described in the VM Reference Manual A number of objects in the Self world are used to interface to foreign data objects and functions These objects are found in the name spaces traits foreign and globals foreign One difficulty in interfacing between Self and external data and functions is that references to foreign data and func tions from within Self can become obsolete when the Self world is saved as a snapshot and then read in later possibly on some other wor
60. animation behaviors that can be applied to any morph including motion scaling and color change animations Although autonomous behavior and external animations are implemented using the same underlying mechanism they have different purposes and are specified in different ways The autonomous behavior of a morph is an intrinsic property of that morph For example updating the time is central to being a clock morph Autonomous behavior is 7 8 Animation 99 Self Handbook Documentation Release 2 for Self 4 4 defined in the morph itself External animation behaviors on the other hand are typically transient and imposed from outside For example the Self programming environment gives feedback for certain actions by wiggling the relevant morph An external animation is specified by creating a separate animation activity object and applying it to the morph to be animated Animation is orthogonal to autonomous behavior for example a clock morph would continue to run even while a motion animation whisked it across the screen 7 8 1 Stepping The autonomous behavior of a morph is defined by its step method For example to make a simple digital clock one could add the following slot to a copy of labelMorph step label time current timeString The clock is activated by asking the system to send the step message to it either continuously every display update cycle or at periodic intervals e g once per second Mak
61. any object that inherits defaultBehavior The object x is called the mirror s reflectee A mirror behaves like a keyed collection whose keys are slot names and whose values are mirrors on the contents of slots of the reflectee A mirror can be queried to discover the number and names of the slots in its reflectee and which slots are parent slots A mirror can be used to add and remove slots of its reflectee Iterating through a mirror enumerates objects representing slots of the reflected object such facets are called fake slots For example a method mirror includes fake slots for the method s byte code and literal vectors and elements of vectors and byte Vectors There is one kind of mirror for each kind of object known to the virtual machine small integers floats canonical strings object and byte vectors mirrors blocks ordinary and block methods ordinary and block method activations processes profilers the assignment primitive and ordinary objects called slots because an ordinary object is just a set of slots The prototypes for these mirrors are part of the initial Self world that exists before reading in any script files The file init self moves these prototypes to the mirrors subcategory of the prototypes category of the Lobby namespace Because mirrors is nota parent slot the names of the mirror prototypes always include the mirrors prefix Modules mirror slot init 3 8 Messages Self allows messages to
62. ar any character but oo 6999 10 2 Lexical overview 137 Self Handbook Documentation Release 2 for Self 4 4 10 3 Syntax overview expression constant unary message binary message keyword message expression constant gt self number string object unary message gt receiver unary send resend unary send unary send identifier binary receiver binary send resend binary send message binary send operator expression keyword receiver keyword send resend keyword send message keyword send small keyword expression cap keyword expression receiver expression resend resend identifier object regular object block regular object gt CL LG Y string slot list P code Y block gt T T slot list code Y slot list unannotated slot list annotated slot list annotated slot string slot list list unannotated gt slot slot slot list code expression expression gt slot gt arg slot data slot binary slot keyword slot arg slot argument name data slot slot name slot name lt expression slot name expression unary slot slot name regular object binary slot operator regular object operator identi
63. ar nul1CharError results 9 The type_seal is an int or char expression that is tested against the type seal value in the proxy If the two are different badTypeSealError results The special value ANY_SEAL will match the type seal in any proxy Note that the proxy conversion will fail with null1PointerError if the proxy object it is given encapsulates a NULL pointer 10 The any_oop conversion is an escape it passes the Self object unchanged to the foreign routine 11 The oop conversion is mainly intended for internal use The second argument is the name of an oop subtype After checking that the incoming argument points to an instance of the subtype the pointer is cast to the subtype 12 The any conversion is different from all other conversions in that it expects two incoming Self objects The actions of the conversion depends on the type of the first object in the following way If the first object is an integer the second argument must also be an integer the two integers are converted to C int s the second is shifted 16 bits to the left and they are or ed together to produce the result If the first object is a float it is converted to a C float and the second object is ignored If the first object is a proxy the result is the pointer represented by the proxy and the second argument is ignored If the first object is a byte vector the second object must be an integer which is interpreted as an index into the byte vecto
64. arent noSenderSlot This activation has no sender slot Continued on next page 10 8 Primitives 149 Self Handbook Documentation Release 2 for Self 4 4 Table 10 3 continued from previous page deadProxyError This proxy is dead and can not be used liveProxyError This proxy is live and can not be used to hold a proxy result wrongNoOfArgsError Wrong number of arguments was supplied with call of foreign function nullPointerError Foreign function returned null pointer nullCharError Can not pass byte vector containing null char to foreign function ex pecting a string prematureEndOfInputError Premature end of input during parsing noDynamicLinkerError Primitive depends on dynamic linker which is not available in this sys tem EPERM ENOENT These errors are returned by a UNIX primitive if a UNIX system call executed by the primitive fails The UNIX error codes are defined in usr include sys errno h see this file for details on the roughly 90 dif ferent UNIX error codes The _ErrorMessage primitive sent to an error string returned by any primitive returns a more descriptive version of the error message this is especially useful for UNIX errors 10 8 2 Available primitives A complete list of primitives can be obtained by sending primitiveList to primitives Documentation for a primitive such as _C1one can be obtained using at thus primitives at _Clone A list of primitive names
65. as next button Retry Cut back the stack to this frame then continue the process Revert Cut back the stack to this frame Finish Finish this frame 5 2 4 Enumerators In addition to the Find Slot enumerator Self has other ways to find things Table 4 Enumerators 64 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 Name Function Implementors Finds all the slots with a given name Implementors of Finds all the slots with the given name that take an argument for read write slots only Senders Finds all the methods that send a message with a given name Senders of Finds all the methods that send the corresponding assignment message read write slots only Senders in family Finds all the methods in this object its ancestors and descendants that send a message Senders of in with a given name or the corresponding assignment message family Find Slot Starting from a designated object finds all slots in that object and its ancestors whose name matches a given pattern Case is ignored matches any character matches any series of zero or more characters Also comes in of and in family flavors Methods Containing Finds methods containing the specified string Similar to grep without wildcards Copied down Finds objects copied down see below from this one Children References Finds slots that contain references to the selected
66. ause a lexical error Productions 699 699 normal char escape char any character except V and Ae AD An EAP TA Av Ag 1301 AV 1819 132 numeric escape Ax general digit general digit Ad Ao digit digit digit string normal char escape char numeric escape Al le le ale 2 4 8 Comments Comments are delimited by double quotes Double quotes may not themselves be embedded in the body of a comment All characters including formatting characters like newline and carriage return are part of the body of a comment Productions 6999 6999 comment gt comment char comment char any character except 6999 Example this is a comment 12 When typing strings in the graphical user interface accepts multi line strings but the character based read evalprint loop does not 2 4 Lexical elements 21 Self Handbook Documentation Release 2 for Self 4 4 22 Chapter 2 Language Reference CHAPTER THREE THE SELF WORLD The default Self world is a set of useful objects including objects that can be used in application programs e g integers strings and collections objects that support the programming environment e g the debugger and objects that simply are used to organize the other objects This document describes how this world is organized focusing primarily on those objects meant for use in Self programs It
67. ave like immutable strings of length one There are 256 well known character objects in the Self universe They are stored in a 256 element vector named ascii with each character stored at the location corresponding to its ASCII value Characters respond to the message asByte by returning their ASCII value that is their index in ascii The inverse of asByte asCharacter can be sent to an integer between 0 and 255 to obtain the corresponding character object Module string 3 5 3 Unordered Sets and Dictionaries collection setOrDictionary set sharedSet dictionary sharedDictionary There are two implementations of sets and dictionaries in the system The one described in this section is based on hash tables The one discussed in the following section is based on sorted binary trees The hash table implementation has better performance over a wide range of conditions An unfortunate ordering of element addtions can cause the unbalanced trees used in the tree version to degenerate into an ordered lists resulting in linear access times A set behaves like a mathematical set It contains elements without duplication in no particular order A dictionary implements a mapping from keys to values where both keys and values are arbitrary objects Dictionaries implement the usual collection behavior plus keyed access using at and at Put and the dictionary specific operations includesKey and removeKey In order to store an object in a set or use i
68. avior of all copies to be changed at once one can move shared behavior and state into a shared traits object Self s object literal syntax can be used to create a new object to be used as the shared traits As a shortcut rather than creating an empty traits object and then adding a parent slot to it an object containing an initialized parent slot can be created in a single operation Evaluate the expression in an evaluator on the outliner use the middle button 7 3 Morph Traits and Prototypes 85 Self Handbook Documentation Release 2 for Self 4 4 menu command Evaluator to open an evaluator on the outliner if necessary parent traits morph This creates a new object whose parent is traits morph To make the new morph inherit through the new traits object invoke the Grab pointer command by pressing the middle button menu on the button on the right side of the parent slot of the morph Drop the end of the pointer onto the new traits object to make the parent slot of the morph point to the new morph This technique is called arrow dragging 4an object lt 370 gt E _ Module Werent traits morph 4an object lt 8 type morph Modules morph morphSaving parent wats mor ph baseDrawOn aCanvas TA alanvas fillArchlithint baseBounds From 0 Spanning 360 Color color self isRectangular false middleMouseDown evt ma tmp tmp color color otherColor otherColor tmp self other
69. bably has the least research ambition in it We simply needed to concentrate the innovation in other areas language design compiler technology user interface The Self programming environment strives to meet the high standard set by Smalltalk s but with a more concrete feels The transporter on the other hand is somewhere in between completely innovative research and dull development It attempts to pull off a novel feat programming live objects instead of text and partially succeeds Its novelty lies in its view of programs as collections of slots not objects or classes and its extraction of the programmer s intentions from a web of live objects Since Self 4 0 the environment has evolved a little mostly in the form of new affordances On the Macintosh Self 4 1 uses option click for a middle mouse click and uses command the apple key click for the right button click So wherever the text says left button click just click with the mouse where it says middle button click hold down the option key and click with the mouse and where it says right button click hold down the command key and click with the mouse I use a Kensington Turbo Mouse with the buttons mapped appropriately These mappings are defined in Self so you can change them by editing the whichButton method in the initialization category in traits ui2MacEvent 5 2 Browsing Concepts 5 2 1 Introducing the Outliner Objects in the Self 4 1 environmen
70. background menu to get the changed modules morph Then press the little button marked w to the right of ovalModule The system will save the code for the module in a file named ovalModule in the applications subdirectory of the current working directory If this directory doesn t exist the system will complain Create the directory and try the fileout operation again The oval morphs module can later be loaded into a snapshot by evaluating the expression bootstrap read ovalModule From applications 7 3 3 Morph Creation The Top down Approach The top down approach to creating a new morph is similar to the approach just described except that one plans to make a first class citizen from the beginning Thus the order of steps is slightly different Here is a brief outline of the procedure 1 Add a slot to the traits namespace object using Add Slot ovalMorph parentx traits morph 2 Add a slot to the globals namespace object ovalMorph parent traits ovalMorph 3 Make each new slot be the creator of its contents using Make creator 4 Set the copy down parent of the prototype to morph via Show annotation on its outliner 5 Set the module of the two namespace slots to ovalModule creating the new module in the process 7 3 Morph Traits and Prototypes 91 Self Handbook Documentation Release 2 for Self 4 4 Slot prototype is already present in
71. be accomplished by inserting space filling morphs between the buttons lt buttonl gt lt spacer gt lt button2 gt lt spacer gt lt button3 gt When the row is stretched the extra space is divided evenly between the two spacers button2 stays in the center and button3 stays at the far right By making the color of the spacers match that of the underlying row they become effectively invisible This is a common technique Figure 7 14 Figure 14 Using flexible spacer morphs to space buttons evenly within a row Normally these spacers would be made the same color as the row making them effectively invisible 7 7 3 Shrink Wrapping It is sometimes desirable for the size of a morph to depend on the sizes of its submorphs For example the size of a button should depend on the size of its label It would be annoying if it didn t the programmer would have to manually resize the button after changing the label A morph designated as shrink wrap shrinks or grows to the smallest size that accommodates the size requirements of its submorphs 7 7 4 Minimum Sizes Morphs have a minimum size in each dimension minWidth and minHeight These sizes determine the minimum amount of space that will be allocated to a morph during layout The minimum size of a morph takes into account the minimum sizes of its submorphs For example the minimum width of a row is the sum of the minimum widths of its submorphs plus a little bit for a border if it has one
72. be manipulated as objects when convenient For example if an object fails to understand a message the object is notified of the problem via a message whose arguments include the selector of the message that was not understood While most objects inherit default behavior for handling this situation by halting with an error it is Sometimes convenient for an object to handle the situation itself perhaps by resending the message to some other object Objects that do this are called transparent forwarders An example is given in interceptor A string has the basic ability to use itself as a message selector using the messages sendTo normal message sends resendTo resends or sendTo DelegatingTo delegated sends Each of these messages has a number of variations based on the number of arguments the message has For example one would used sendTo With With to send a message with at Put as the selector and two arguments 32 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 at Put sendTo aDict With k With v Note Primitives such as _Print cannot be sent in the current system A selector receiver delegatee methodHolder and arguments can be bundled together in a message object The message gets sent when the message object receives the send message Message objects are used to describe delayed actions such as the actions that should occur just before or after a snapshot is read They are
73. ca Style bold Size 14 FontSpec s encapsulate some attributes of a font and in the future should perhaps encapsulate the color as well 1 The rest of this section has been written in 1999 under time pressure to get Self 4 1 out so I can get back to other things John bears no responsibility for its shortcomings You can send questions about this to me David Ungar at david ungar sun com 7 12 The Graphical Environment 107 Self Handbook Documentation Release 2 for Self 4 4 108 Chapter 7 Morphic The Self User Interface Framework CHAPTER EIGHT VIRTUAL MACHINE REFERENCE 8 1 Startup options The following command line options are recognised by the Virtual Machine f filename Reads filename which should contain Self source immediately after startup after reading the snapshot and evaluates the contents Useful for setting options installing personal shortcuts etc h Prints a message describing the options p Suppresses execution of the expression snapshotAction postRead after reading a snapshot Useful 1f something in the startup sequence causes the system to break s snapshot Reads initial world from snapshot A snapshot begins with the line exec Self s 0 which causes the Virtual Machine to begin execution with the snapshot Don t print warnings about object code w These options are provided for use by Self VM implementors F Discards any machine code saved
74. cast to this pointer type is passed to the foreign routine It is the responsibility of the foreign routine not to go past the end of the byte vector The foreign routine should not retain pointers into the byte vector after the call has terminated Note canonical strings can not be passed through a bv conversion badTypeError will result This is to ensure that they are not accidentally modified by a foreign function 5 This conversion passes two values to the foreign routine a pointer to the first byte in the byte vector and an integer which is the length of the byte vector divided by sizeof ptr_type If the size of the byte vector is not a multiple of sizeof ptr_type badSizeError results 6 In addition to accepting a byte vector this conversion accepts the integer 0 in which case a NULL pointer is passed to the foreign routine 126 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 7 The cbv conversions are like the bv conversions except that canonical strings are allowed as actual arguments A cbv conversion should only be used if it is guaranteed that the foreign routine does not modify the bytes it gets a pointer to 8 All the string conversions take an incoming byte vector copy the bytes part add a trailing null char and pass a pointer to this copy to the foreign routine After the call has terminated the copy is discarded If the byte vector contains a null ch
75. cess b to resume execution of the process in the background s to suspend execution of the process for process 25 k Process 25 killed Self 10 gt In this example the loop was interrupted by typing Control C and the process menu was used to abort the process If the user had typed q to quit the scheduler all current processes would have been aborted along with the scheduler itself Select a process or q to quit scheduler q Scheduler shut down prompt VM The scheduler has been stopped returning the user to the VM prompt The command prompt start restarts the scheduler VM prompt start Self 11 gt Although the VM prompt can be used to evaluate expressions directly the scheduler supports much nicer error messages and debugging so it is usually best to run the scheduler The scheduler is started automatically when the default world is created Certain virtual machine operations like garbage collection reading a snapshot and compilation cannot be interrupted interrupts during these operations will be deferred until the operation is complete As a last resort e g if the system appears to be hung you can force an abort by pressing Control five times in a row 1 Normally you would use debugging facilities provided in the programming environment 36 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 3 15 Using the textual debugger If you are modifying th
76. cessor that understands instructions like push receiver or send the x message In fact Self bytecodes correspond much more closely to source code than say Smalltalk 80 bytecodes See CUL89 for a list of the Self byte codes The raison d tre of the virtual machine is to pretend that these bytecodes are directly executed by the computer the programmer can explore the Self world down to the bytecode level but no further This pretense ensures that the behavior of a Self program can be understood by looking only at the Self source code The second stage of translation is the actual compilation of the bytecodes to machine code This is how the execution of bytecodes is implemented it is totally invisible on the Self level except for side effects like execution speed and memory usage The compilation takes place the first time a message is actually sent thus the first execution of a program will be slower than subsequent executions Actually this explanation is not entirely accurate the compiled method is specialized on the type of the receiver If the same message is later sent to a receiver of different type e g a float instead of an integer a new compilation takes place This technique is called customization see CU89 for details Also the compiled methods are placed into a cache from which they can be flushed for various reasons therefore they might be recompiled from time to time Furthermore the current
77. clared Methods Containing Move New Shell On a module morph enumerates its slots Summons a list of changed modules Enumerate an object s children Clean up the screen collapse outliners and stack them on the left of the window Manually initiate a garbage collection Can help when you know you have just freed up a bunch of space Self also does this automatically Collapses all outliners or all categories within an outliner or category Enumerate an object s copy down children Show an object s copy down parent Copies slots categories or text Summons an object for manipulating morphs For a slot create a button to send the message to the object The receiver may be set by carrying the button on top of the receiver and using the middle button on the button The button is grabbed with either the car pet morph or with the grab right menu item Bug buttons do not mani fest their results Copies text to the text buffer Evaluate the selected text do not show the result Evaluate the text in the editor do not show the result On a slot open an editor to change its name slot type or contents Adds an evaluator window to an object outliner Expand all subcategories On the changed module morph shows a list of slots not included in any module On a debugger stack enable or disable filtering Searches an object and its ancestors for slot names matching a pattern For an assignable slot x show all slots named
78. corative or information content for user interfaces labelMorph displays a single line string in a single font style size and color circleMorph displays a filled circle pixmapMorph displays an image currently at most 8 bits deep movieMorph cycles through a sequence of images as it is stepped 104 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 The library includes two kinds of text editors editorMorph a general editor that allows arbitrary morphs to be embedding in the text uglyTextEditor a simple text only editor that is a bit faster for editing larger amounts of text Many applications implement specialized content morphs For example the Self programming environment defines morphs that represent Self objects slots and categories 7 12 The Graphical Environment Morphic hides many details of the underlying graphics system This both simplifies programming and provides porta bility the layer of abstraction between the programmer and the underlying graphics system allows the implementation of the low level graphics to be changed without affecting programs written by clients While the current version of the system is built on the X window system 1t could be ported to other window systems fairly easily although the target window system should support color or grayscale for good results One might even create a Postscript implementation of the morphic graphics inter
79. ct delegated send with arg vector indirect resend indirect resend with arguments in a vector Message object protocol 77 Self Handbook Documentation Release 2 for Self 4 4 send fork receiver selector methodHolder delegatee arguments receiver Selector receiver Selector Arguments receiver Selector Type Delega tee MethodHolder Arguments perform the send described by a message object start a new process the new process performs the message set receiver set selector set method holder set delegatee of the message object set arguments packaged in a vector set receiver and selector set receiver selector and arguments set all components Reflection mirrors reflect reflectee contentsAt isAssignableAt isParentAt isArgumentAt parentPriorityAt slotAt contentsAt visibility At returns a mirror on the argument returns the object the mirror receiver reflects returns a mirror on the contents of slot n tests if slot n is an assignable slot tests if slot n is a parent slot tests if slot n is an argument slot returns the parent priority of slot n returns a slot object representing slot n returns the contents of the slot named n returns a visibility object representing visibility of slot n System wide Enumerations messages sent to the oddball object browse all Limit referencesOf Limit referencesOfReflectee Limit childrenOf Lim
80. ctions This section gives a description of a complete application which uses foreign functions The aim is to present a realistic and complete example of how foreign functions may be used The complete source for the example is found in the directory objects applications serverDemo in the Self distribution The example used is an application that allows Self expressions to be easily evaluated by non Self processes Having this it then becomes possible to start Self processes from a UNIX prompt shell or to specify pipe lines in which some of the processes are Self processes For example in proto cat someFile tokenize sort r capitalize tee lst it may be the case that the filters tokenize and capitalize perform most of their work in Self Likewise the command proto mail may invoke some fancy mail reader written in Self rather than the standard UNIX mail reader To see how the above can be accomplished please refer to Figure 5 below The left side of the figure shows the external view of a typical UNIX process It has two files stdin and stdout for simplicity we ignore stderr Stdin is often connected to the keyboard so that characters typed here can be read from the file stdin Likewise stdout is typically connected to the console so that the process can display output by writing it to the file stdout Stdin and stdout can also be connected to regular files if the process was started with redirection The right side of Fig
81. ctivation objects Thus a message sent explicitly to self is not equivalent to an implicit receiver send because the former won t search local slots before searching the receiver Explicitly sending messages to se1f is considered bad style Examples factorial implicit receiver unary message 3 implicit receiver binary message max 5 implicit receiver keyword message 1 power 3 parsed as 1 power 3 Accesses to slots of the receiver local or inherited are also achieved by implicit message sends to self For an assignable data slot named t the message t returns the contents and t 17 puts 17 into the slot 2 3 5 Resending messages A resend allows an overridding method to invoke the overridden method Directed resends allow ambiguities among overridden methods to be resolved by constraining the lookup to search a single parent slot Both resends and directed resends may change the name of the message being sent from the name of the current method and may pass different 2 3 Expressions 15 Self Handbook Documentation Release 2 for Self 4 4 arguments than the arguments passed to the current method The receiver of a resend or a directed resend must be the implicit receiver Intuitively resend is similar to Smalltalk s supersend and CLOS call next method A resend is written as an implicit receiver message with the reserved word resend a period and the message name No whitespace may separate resend t
82. cuted it performs the following steps 1 Check that the arguments supplied have the correct types 2 Convert the arguments from Self representation to the representation that the foreign routine needs 3 Invoke the foreign routine on the converted arguments 4 Convert the return value of the foreign routine to a Self object and return this as the Self level result 8 13 Interfacing with other languages 117 Self Handbook Documentation Release 2 for Self 4 4 To make it easier to write glue code a special purpose language has been designed for this The result is that glue for a foreign routine will often consist of only a single line The glue language is implemented as a set of C preprocessor macros Therefore glue code is just a rather peculiar kind of C Glue code can be in a file of its own or if it is glue for calling C routines it can be in the same file as the foreign routines and compiled with them To make the definition of the glue language available the file containing glue code must contain include _glueDefs c incl The file _glueDefs c incl includes a bunch of C header files that contain all the definitions necessary for the glue Of the included files glueDefs h is probably the most interesting in this context It defines the glue language and also contains some comments explaining it Since different foreign languages have different type systems and calling conventions the glue
83. d and new size or position Typically the implementor of a morph writes code to send the changed message automatically after updating any slot that affects the morph s appearance For example the color message defined in traits morph sends changed automatically Likewise external animation activities report appropriate changes Thus the client of a morph usually need not send changed explicitly 7 9 Other Issues 101 Self Handbook Documentation Release 2 for Self 4 4 7 9 4 Layout Updating Morphic also maintains morph layout incrementally When a morph is changed in a way that could influence layout e g when a new submorph is added to it the message layoutChanged is sent to the morph This triggers a chain of activity First the layout of the changed morph is updated This may change the amount of space apportioned to some of its submorphs causing their layouts to be updated Then if the space requirements of the changed morph have changed e g if it needs more space to accommodate the newly added submorph the layout of its owner is updated and possibly its owner s owner and so on In some cases the layout of every submorph in a deeply nested composite morph may need to be updated Fortunately there are many cases where the layout updates can be localized Morphic detects these cases thus saving a great deal of unnecessary work As with changed messages morph clients usually need not send layoutChanged explicitly si
84. d has been changed to draw unfilled ovals First summon outliners for the globals and traits namespace objects by evaluating the expressions globals and traits in any text editor That is type the expression select it and invoke the Get Expression command in the middle button menu of the editor Then open an appropriate category for the new morph or create a new category Within the chosen category of globals create a slot to hold the new morph s prototype by invoking the Add Slot command and accepting the following expression ovalMorph nil Next invoke the Grab pointer command by pressing the middle button menu on the button on the right side of the new ovalMorph slot Drop the end of the pointer over the new morph prototype and release the mouse This makes the new slot point to the new morph prototype Repeat the procedure just described to create an ovalMorph slot in the traits namespace and point it to the traits object for the new morph Finally invoke the Make creator middle button menu command on each new ovalMorph slot to designate it as that morph s creator This informs the system that the given slot is the given object s home in the global namespace An object may be reachable via several global slots setting its creator path distinguishes one of these slots as the object s official home address This information is used to determine the object s name as well
85. d of the row then the next submorph will be placed to the right of the first and so on The last submorph will be placed at right most end of the row Notice that the order of the submorphs is not affected by the packing process Also notice that the packing is done only in one primary dimension the horizontal dimension in this case The other dimension is also considered during packing and is controlled by the justification parameter of the row Depending on this parameter the tops bottoms or centers of the submorphs can be aligned with the top bottom or center of the row 7 6 Drag and Drop 97 Self Handbook Documentation Release 2 for Self 4 4 7 7 2 Space filling For simplicity the packing strategy was described as if the submorphs to be packed were all rigid In order to support stretchy layouts morphs can be designated as space filling Note The source code uses the older term flexible When there is extra space a space filling morph expands to fill this space If there is no extra space a space filling morph shrinks to its minimum size When there are several space filling morphs in a single row or column any extra space is divided evenly among them Space filling morphs can be used to control the placement of submorphs within the primary dimension when a row or column is stretched For example suppose one wanted a row with three buttons one at the left end one at the right end and one in the middle This can
86. d to In general var may be any expression that in a global context evaluates to an 1 value 8 13 Interfacing with other languages 121 Self Handbook Documentation Release 2 for Self 4 4 e expr_c0 expr_a0 when assigning to a variable the value it is assigned is obtained by converting a Self object to a C value The expr_c0 expr_a0 pair which can be any one of the argument conversions listed in Table 3 specifies how to do this conversion 8 13 8 Reading and assigning struct components Reading the value of a struct component or assigning a value to it is similar to doing the same operations on a global variable The difference is that the struct must somehow be specified This is taken care of by the macros C_get_comp and C_set_comp The general syntax is C_get_comp cnvt_res aux_res cnvt_strc aux_strc comp gfname C_set_comp cnvt_strc aux_strc comp expr_c0 expr_a0 gfname Here is an example assigning to the sin_port field of a struct sockaddr_in this struct is defined in usr include netinet in h struct sockaddr_in short sin_family u_short sin_port struct in_addr sin_addr char sin_zero 8 y The struct is represented by a proxy object char socks type seal for sockaddr_in proxies C_set_comp proxy sockaddr_in socks sin_port short set_sin _port_glue The sockaddr_in example defines a function set_sin_port_glue which can be called from Self The function takes tw
87. dAt pt Diameter d Color c outline or fill a wedge cut by the given angles from an ellipse bounded by the given rectangle 7 12 The Graphical Environment 105 Self Handbook Documentation Release 2 for Self 4 4 arcWithin r From startAngle Spanning spanAngle Color c arcWithin r From startAngle Spanning spanAngle Width w Color c fillArcWithin r From startAngle Spanning spanAngle Color c draw a simple or compound curve bezier pti Control cl Control c2 To pt2 Width w Color c bSpline controlPoints Width w Color c catmullRomSpline controlPoints Width w Color c draw text in the given font and size text s At pt Font fName Size fSize Color c display a portable pixel based image a ui2Image image i At pt Canvases maintain an offset allowing graphic operations to be automatically translated Canvases also maintain a scale factor but scaling is not currently used and is probably buggy Furthermore image scaling is not implemented In morphic unlike many graphics packages the graphics context is hidden from the programmer all the common parameters that control the behavior of a given drawing command such as color and line width are passed as explicit parameters A few infrequently changed parameters such as the fill pattern and the clipping rectangle can be changed temporarily via messages such as withPattern Do and withClip Do The canvas handles these messages by changing the state of t
88. do not need this slot at all and so omit it Most other object oriented programming systems would not allow a subclass to avoid inheriting an instance variable The Self 4 1 programming environment uses the copy down information to allow the programmer to use a class based style when appropriate For example if the programmer adds a slot to morph the environment will offer to add it to circleMorph too If the programmer should use a text editor to edit the definition of morph the circleMorph object will be changed after rereading both object s text files The least convenient aspect of using copy downs is that to do the moral equivalent of creating a subclass the programmer has to create two objects a new traits object and a new prototype and then set the object annotation of the new prototype Perhaps someday there will be a button to do this or perhaps other styles of programming will emerge This concludes a brief tour of the Self 4 1 programming environment Although we strove for simplicity in the design of Self its programming environment includes a fair amount of functionality which may take a while to learn We hope that you find the investment worth the reward Footnotes 72 Chapter 5 How to Program in Self CHAPTER SIX USEFUL SELECTORS This is a list of selectors which Selfers should find useful as a starting point Copying clone shallow copy for use within an object clients should use copy copy copy
89. drawn icons directly into a program and it is hard to write applications whose data domain is really programs 5 4 2 Data Program For Self we have gone a different way following in the footsteps of Smalltalk and Lisp A Self program consists of live objects Self has no edit run mode To change an object you do not retreat to a source file or even to a class you just change the object itself This immediacy and concreteness lessens the cognitive burden on the programmer smooths the learning curve and hastens gratification However this stance creates a big problem the moment you need to move a program from one world of objects to another it is very hard to pin down what to do For example suppose an object contains a slot with 1024 in it Should that value be copied literally Perhaps it is the result of some computation such as the width of the current screen and should be recomputed instead There simply is not enough information in a Self object to extract programs from Snapshots 5 4 3 Changes vs Pieces Earlier in the project we considered constructing a calculus of changes that could be used to represent programs and then moving programs by reapplying the changes to the new snapshot But we had enough on our plate and rejected this approach as too ambitious to tackle without a dedicated graduate student Instead we decided to represent programs as pieces that could be filed out of a snapshot and filed in to another To
90. e Save as above To have the transporter record the current contents of a slot choose Follow Slot To have it ignore the current value and just record a given expression for the slot s initial value use the Initial Contents option 5 3 Hacking Objects 67 Self Handbook Documentation Release 2 for Self 4 4 5 4 The Transporter The transporter has been built in order to move programs from one world of objects to another so you can ignore it as long as you work with just one snapshot However if you want to give your program to someone else or save it as source or read it in to a newer snapshot you will need to learn about the transporter 5 4 1 The Traditional Schism between Program and Data What is a program In most systems it is a piece of text although in more advanced environments it may have structure It is a description that can be used to create an activity a running program that can then operate on data In the conventional view Table 6 The Schism between Program and Data Program Data Who can change it The programmer The user When can it change At programming time At execution time How is it changed With a text editor By running a program This model grew up in an era where computers were too small to host both compilers and applications at the same time Although it has some virtues it makes other operations very hard it is hard to include data such as hand
91. e accept function is more general than what is needed for this application so a wrapper function simple_accept has been written The result is that the server needs to call only three foreign functions socket_bind_listen simple_accept and shutdown Glue for these three functions and the source for the first two is found in the file socks c This file is compiled and linked using the Makefile The result is a shared object file socks so 8 13 20 Use of foreign functions in server self The server program is implemented using foreignFct objects There is only a few lines of code directly involved in setting this up First the foreignFct prototype is cloned to obtain a local prototype called socksFct which contains the path for the socks so file socksFct is then cloned each time a foreignFct object for a function defined in socks so is needed For example in traits socket the following method is found copyPort portNumber Create a socket do bind then listen sbl socksFct copyName socket_bind_listen_glue sbl value portNumber With deadCopy Y This method copies a socket object and returns the copy The local slot sb1 is initialized to a foreignFct object The body of the method simply sends value With to the foreignFct object The first argument is the port number to request for the socket the second argument is a deadCopy of self socket objects are proxies and socket_bind_listen returns a proxy so it mus
92. e core of the programming environment or working without the environment you may need to use the textual debugger After attaching the aborted process to the debugger using the shell command attach these commands are available Command Description attach n attach the process with object reference number n detach detach the debugged process step n execute n non trivial bytecodes stepi n execute n bytecodes next n execute n non trivial bytecodes in the current activation nexti n execute n bytecodes in the current activation finish finish executing the current activation cont continue execution trace print out a stack trace of the process show display the current activation show n go to and display the nth activation on the stack status display the status of the debugged process up n go up n activation s upLex go up to the lexical enclosing scope of this activation down n go down n activation s lookup lt name gt lookup the given name in the context of the current activation A bytecode is trivial if it is a push of a literal or a send to a slot residing in the lexical scope of the current activation 3 15 Using the textual debugger 37 Self Handbook Documentation Release 2 for Self 4 4 38 Chapter 3 The Self World CHAPTER FOUR A GUIDE TO PROGRAMMING STYLE This section discusses some programming idioms and stylistic conventions that have evolved in the Self gr
93. e other hand a list object is not unique There may be many lists in the system each containing different elements A unique object responds to the message copy by returning itself and uses identity to test for equality The general rule is e unique objects usually inherit from traits oddball non unique objects usually inherit from traits clonable Module rootTraits 3 2 3 Mixins Like traits objects mixin objects encapsulate a bundle of shared behavior Unlike traits objects however mixin objects are generally parentless to allow their behavior to be added to an object without necessarily also adding unwanted behavior such as access to the lobby namespace Mixins are generally used in objects that also have other parents An example ismixins identity 3 2 4 The Identity Mixin Two objects are usually tested for equality based on whether they have the same value within a common domain For example 3 0 3 within the domain of numbers even though they are not the same object or even the same kind of object In some domains however two objects are equal if and only if they are the exact same object For example even two process objects with the same state are not considered equal unless they are identical In such cases identity comparison is used to implement equality tests and mixins identity can be mixed in to get the desired behavior Module rootTraits 3 3 Blocks Booleans and Control Structures A block is a specia
94. e sure the labelMorph is visible in the world use the Show Morph menu command if necessary then in an evaluator on its outliner evaluate getSteppedEveryMSecs 1000 This will cause the step message to be sent to the morph once per second i e every 1000 milliseconds causing it to display a formatted string representing the current time Step messages are sent synchronously during the display update cycle This has the advantage of simplifying synchronization but requires that step methods complete quickly to avoid delaying user interactions The message stopGettingStepped can be sent to the morph to turn off stepping for that morph Morphic automatically stops stepping when the target morph is removed from the world To make the clock morph reactivate itself when dropped back into the world add the following slot justDroppedInto m Event evt isInWorld ifTrue getSteppedEveryMSecs 1000 7 8 2 External Animation External animation of a morph is achieved by scheduling an animation activity with that morph as its target An animation activity changes some property of its target gradually over the course of a number of display cycles frames For example a positionAnimator animates a change in its target morph s location The programmer specifies the initial and final values of the property to be changed e g the starting and ending position and the duration over which the change should occur The durat
95. e_seal If the pointer is n often n is NULL the conversion fails with a UNIX error similar to the way int_or_errno may fail The fct_proxy fct_proxy_null and fct_proxy_or_errno conversions are similar to the corre sponding proxy conversions The difference is that they produce a fct Proxy object rather than a proxy object Also their second part is a triple rather than a pair The extra component specifies how many arguments the function takes if called The special keyword unknownNoOfArgs or any nonnegative integer expression can be used here 128 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 7 This conversion is an escape it passes the C value unchanged to Self It is an error to use it if the C value is not an oop 8 The proxy fctProxy object that is returned by these conversions is not being created by the glue code Rather a proxy fctProxy must be passed down from the Self level This proxy fctProxy a result proxy will then be side effected by the glue the value that the foreign function returns will be stored in the result proxy together with the requested type seal It is required that the result proxy is dead when passed down else a liveProxyError results After being side effected and returned the result proxy is live The result proxy is the last argument of the function that the glue macro expands to 8 13 16 A complete application using foreign fun
96. ed Two objects are equal 1f they mean the same thing For example 3 3 0 even though they are different objects and have different repre sentations Two objects are identical if and only if they are the same object Or more precisely two references are identical if they refer to the same object The primitive _Eq tests if two objects are identical Finally two objects are indistinguishable if they have exactly the same behavior for every possible sequence of non reflective messages The binary operator tests for indistinguishability Identity implies indistinguishability which implies equality It is actually not possible to guarantee that two different objects are indistinguishable since reflection could be used to modify one of the objects to behave differently after the indistinguisability test was made Thus is defined to mean identity by default Mirrors however override this default behavior m1 m2 if m1 reflectee _Eq m2 reflectee This makes it appear that there is at most one mirror object for each object in the system This illusion would break down however if one added mutable state to mirror objects 44 Chapter 4 A Guide to Programming Style CHAPTER FIVE HOW TO PROGRAM IN SELF 5 1 Introduction The Self programming environment provides facilities for writing programs and the transporter provides a way to save them as source files Of all the parts of Self the programming environment pro
97. ed things up When checked only wellknown i e filed out see below objects are searched which is much faster 5 3 Hacking Objects Hacking the discipline of making fine furniture from trees using an axe In going through this document you have already added a slot and edited methods in both object outliners and debug gers In addition Self 4 1 has many other ways to change an object Table 5 Ways to change an object Removing Moving Copying Categories 5 3 Hacking Objects 65 Self Handbook Documentation Release 2 for Self 4 4 Ways to change an object How Why Removing a category Add slot or category to object or category Moving a category Copying a category Removing Moving Copying Cat egories Move in category middle menu then drag the category to the back ground or the trash can Add Category in object or cate gory middle menu then type in the new category name then hit green button to accept Move in category middle menu then drag to another object Copy in category or category middle menu then drag the cate gory to another object Removing a category Adding a new category Copying a category Copying a category Removing a slot Add slot to object or category Moving a slot Removing Copying Slots Move in slot middle menu then drag the slot to the background or the trash can Add Slot in object or catego
98. ement Thus the t reeSet object now behaves as a treeSetNode object 30 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 with right and left subtrees initially copies of the empty subtree treeSet Dynamic inheritance allows one object to behave modally without using clumsy if tests throughout every method One caveat since these trees are not balanced they can degenerate into lists 1f their elements are added in sorted order However a more complex tree data structure might obscure the main point of this implementation to provide a canonical example of the use of dynamic inheritance Modules tree 3 5 5 Lists and PriorityQueues collection list priorityQueue A list is an unkeyed circular doubly linked list of objects Additions and removals at either end are efficient but removing an object in the middle is less so as a linear search is involved A priorityQueue is an unkeyed unordered collection with the property that the element with the highest priority is always at the front of the queue Priority queues are useful for sorting heapsort and scheduling The default comparison uses lt but this can be changed Modules list priorityQueue 3 5 6 Constructing and Concatenating Collections clonable collector Two kinds of objects play supporting roles for collections A collector object is created using the amp operator inherited from defaultBehavior and represents a collectio
99. enough because some of the morphs within a composite morph may refer to other morphs within the composite For example the buttons of a radarView refer to the radarDisplay morph When a radarView morph is copied the buttons of the copy must be updated to point to the radarDisplay morph in the copy not that in the original radarView A simplified diagram of this process is shown in Figure 16 Sometimes a morph may need to do something special when it is copied In this case the message baseCopy should be overridden rather than copy See traits ui2Button for an example of how this is done 7 10 Morph Responsibilities There are two messages that each type of morph is expected to implement morphTypeName and prototype The first returns a string used to show the type of a morph in the user interface e g in the core sampler while the second which should return the prototype for the morph is used by the morph filing out code Two other messages may need to be overridden These are isRectangular This message is used to optimize the drawing of shadows for morphs whose display com pletely fills their bounding rectangle The default implementation returns true so non rectangular morphs such as circleMorphs must provide an implementation that returns false Hint If a non rectangular morph casts a rectangular shadow someone probably forgot to override this message mapReferencesUsing This message is sent during copying to update any reference
100. epeatedly tried simpler schemes However all of the capabilities in the current scheme seem to be essential in some case This issue remains as a question for future work 5 4 6 Copy Down Because Self eschews classes and because the current compiler cannot optimize dynamic inheritance it is necessary to copy down slots when refining an object For example the prototypical morph object contains many slots that every morph should have and some mechanism is needed to ensure that their presence is propagated down to more specialized morphs like the circleMorph In a class based language this need is met by a rule ensuring that subclasses include any instance variables defined in their superclasses In Self this inheritance of structure is separated from the inheritance of information performed by the normal hierarchy of parent slots Instead of including a facility for inheriting structure in the language Self 4 1 implements a facility in the environment called copy down An object s annotation can contain a copy down parent copy down selector and set of slots to omit The copy down parent is sent the message given by the copy down selector and except for the slots to omit the slots in the result are added to the object Copied down slots are shown in pink in the outliner For example here are the prototypical morph and the prototypical circleMorph 4circleMorph type circleMorph E Creator slot citcleMorph Complete Yes No
101. er Selector receiver Selector Arguments receiver Selector Type Delega tee MethodHolder Arguments perform the send described by a message object start a new process the new process performs the message set receiver set selector set method holder set delegatee of the message object set arguments packaged in a vector set receiver and selector set receiver selector and arguments set all components Reflection mirrors reflect reflectee contentsAt isAssignableAt isParentAt isArgumentAt parentPriorityAt slotAt contentsAt visibility At returns a mirror on the argument returns the object the mirror receiver reflects returns a mirror on the contents of slot n tests if slot n is an assignable slot tests if slot n is a parent slot tests if slot n is an argument slot returns the parent priority of slot n returns a slot object representing slot n returns the contents of the slot named n returns a visibility object representing visibility of slot n System wide Enumerations messages sent to the oddball object browse 10 5 Useful Selectors 143 Self Handbook Documentation Release 2 for Self 4 4 all Limit referencesOf Limit referencesOfReflectee Limit childrenOf Limit implementorsOf Limit sendersOf Limit returns a vector of mirrors on all objects in the system up to the limit returns a vector of mirrors on all objects referring t
102. er to use the second form In a similar vein blocks inherit default behavior that allows one to provide a block taking fewer arguments than expected For example the collection iteration message do expects a block taking two arguments a collection element and the key at which that element is stored If one is only interested in the elements not the keys one can provide a block taking only one argument and the second block argument will simply be ignored That is you can write myCollection do el el printLine instead of myCollection do el key el printLine 4 6 nil Considered Naughty As in Lisp Self has an object called nil which denotes an undefined value The virtual machine initializes any uninitialized slots to this value In Lisp many programs test for nil to find the end of a list or an empty slot in a hash table or any other undefined value There is a better way in Self Instead of testing an object s identity against nil define a new object with the appropriate behavior and simply send messages to this object Self s dynamic binding will do the rest For example in a graphical user interface the following object might be used instead of nil nullGlyph display self boundingBox 0 0 0 0 mouseSensitive fals 1 To make it easier to avoid nil the methods that create new vectors allow you to supply an alternative to nil as the initial value for the new vector s elements e
103. ered incremental algorithm to keep the screen updated This algorithm is efficient it tries to do as little work as possible to update the screen after a change and high quality the user does not see the screen being repainted It is also mostly automatic many applications can be built without the programmer ever being aware of how the display is maintained The description here is mostly for the benefit of those curious about how the system works Each morphic screen window displays the contents of some worldMorph A worldMorph keeps a list of rectangular damaged regions of the screen Every morph can compute a rectangle that encloses its entire visible representation When a morph changes its appearance for example its color it sends itself the message changed This causes its bounding rectangle to be translated into global coordinates and added to the damage list of the worldMorph that contains it This worldMorph is found by starting at the morph and following the owner chain the worldMorph is the last morph in this chain On the next display update cycle the worldMorph redraws the portions of all morphs that intersect rectangles in the damage list via an off screen buffer including the morph that was changed The world Morph then clears its damage list to prepare for future damage reports When a morph changes size or position damage is reported both before and after the change This causes the screen to be updated at both the ol
104. es alternative constructions gt production separates the left and right hand sides of a production A glossary of terms used in this document can be found in Appendix A 2 1 Objects Objects are the fundamental entities in Self every entity in a Self program is represented by one or more objects Even control is handled by objects blocks 2 1 7 are Self closures used to implement user defined control structures An object is composed of a possibly empty set of slots and optionally code 2 1 5 A slot is a name value pair slots contain references to other objects When a slot is found during a message lookup 2 3 6 the object in the slot is evaluated Although everything is an object in Self not all objects serve the same purpose certain kinds of objects occur fre quently enough in specialized roles to merit distinct terminology and syntax This chapter introduces two kinds of objects namely data objects plain objects and the two kinds of objects with code ordinary methods and block methods 2 1 1 Syntax Object literals are delimited by parentheses Within the parentheses an object description consists of a list of slots delimited by vertical bars I followed by the code to be executed when the object is evaluated For example slotl slot2 here is some code printLine Both the slot list and code are optional 11 and each denote an empty object 1 Tf you wish to use t
105. ethod Now the debugger shows the source of the method with the actual message being sent highlighted In this case it is just the whole thing One of the conveniences in the Self programming environment is that you do not have to go back to the original method to fix it but can just fix it here following the grand tradition of Lisp and Smalltalk programming environments So use the left button to select the vn and type nv instead then hit the green button to accept the change The green button will stay in a bit longer because when a method is changed from the debugger every slot pointing to that same method is made to feel the change the method is changed in place see the figure below This feature lets you change a method in a clone and simultaneously affect the prototype if you are putting your methods in prototypes instead of traits Changing a method in an ordinary outliner would just affect that one object even if other objects had been cloned from it This rule avoids unintentional changes The more global kind of change performed by the debugger takes a little longer When it is accomplished the red and green buttons will disappear Now os is highlighted to show that the process is about to send os to implicit self Try the Step button which performs a single message send After hitting the Step button twice and a control L to widen the debugger the process will have entered the environmentVariable IfFail met
106. everseSorted copy sorted in descending order copySortedBy copy sorted by custom sort criteria sortedDo iterate in ascending order reverseSortedDo iterate in descending order sortedBy Do iterate in order of custom sort criteria Indexable specific firstKey return the first key lastKey return the last key loopFrom Do circularly iterate starting from element n copyAddFirst return a copy of this collection with element added to beginning copyAddLast return a copy of this collection with element added to end copyFrom return a copy of this collection from element n copyFrom UpTo return a copy of this collection from element n up to element m copy WithoutLast return a copy of this collection without the last element copySize copy with size n copySize FillingWith copy with size n filling in any extra elements with second arg Timing realTime elapsed real time to execute a block cpuTime CPU time to execute a block userTime CPU time in user process to execute a block systemTime CPU time in system kernel to execute a block totalTime system user time to execute a block Message Sending Sending like Smalltalk perform receiver is a string sendTo With sendTo WithArguments sendTo DelegatingTo With sendTo DelegatingTo WithArgu ments resendTo With resendTo WithArguments send receiver string as a message indirect send with arguments in a vector indirect delegated send indire
107. executable code It defines methods for loading and unloading the object file it represents A foreignFct object represents a 3 9 Processes and the Prompt 33 Self Handbook Documentation Release 2 for Self 4 4 foreign routine It understands messages for calling the foreign routine and has associated with ita foreignCode object The foreignFct and foreignCode objects cooperate with the linker to ensure that object files are transparently loaded when necessary and that fct Proxies depending on an object file are killed when the object file is unloaded etc The foreignCodeDB object ensures that foreignCode objects are unique given a path It also allows for spec ifying initializers and finalizers on foreignCode objects An initializer is a foreign routine that is called whenever the object file is loaded Initializers take no arguments and do not return values Typically they initialize global data structures Finalizers are called when an object file is unloaded When debugging foreign routines foreignCodeDB printStatus outputs a useful overview Normal use of a foreign routine simply involves cloning a foreignF ct object to represent the foreign routine When cloning it the name of the function and the path of the object file is specified It is then not necessary to worry about proxy fctProxy and linker objects etc In fact it is recommended not to send messages directly to these objects since this may break the higher level invar
108. f Handbook Documentation Release 2 for Self 4 4 firstKey return the first key lastKey return the last key loopFrom Do circularly iterate starting from element n copyAddFirst return a copy of this collection with element added to beginning copyAddLast return a copy of this collection with element added to end copyFrom return a copy of this collection from element n copyFrom UpTo return a copy of this collection from element n up to element m copy WithoutLast return a copy of this collection without the last element copySize copy with size n copySize FillingWith copy with size n filling in any extra elements with second arg Timing realTime elapsed real time to execute a block cpuTime CPU time to execute a block userTime CPU time in user process to execute a block systemTime CPU time in system kernel to execute a block totalTime system user time to execute a block Message Sending Sending like Smalltalk perform receiver is a string sendTo With sendTo WithArguments sendTo DelegatingTo With sendTo DelegatingTo WithArgu ments resendTo With resendTo WithArguments send receiver string as a message indirect send with arguments in a vector indirect delegated send indirect delegated send with arg vector indirect resend indirect resend with arguments in a vector Message object protocol send fork receiver selector methodHolder delegatee arguments receiv
109. fEmpty doFirstMiddle Last IfEmpty reverseDo iterate with special behavior for first and last iterate with special behavior for first iterate with special behavior for ends iterate with special behavior for last iterate backwards through list with Do co iterate passing corresponding elements to block Reducing max return maximum element mean return mean of elements min return minimum element sum return sum of elements product return product of elements reduce With evaluate reduction block with elements reduceWith IfEmpty evaluate reduction block with elements evaluating block if empty Transforming asByteVector return a byte vector with same elements asString return a string with same elements asVector return a vector with same elements asList return a list with the same elements filterBy Into add elements that satisfy filter block to a collection mapBy add result of evaluating map block with each element to this collection mapBy Into add result of evaluating map block with each element to a collection Sorting sort sort receiver in place copySorted copy sorted in ascending order copyReverseSorted copy sorted in descending order copySortedBy copy sorted by custom sort criteria sortedDo iterate in ascending order reverseSortedDo iterate in descending order sortedBy Do iterate in order of custom sort criteria Indexable specific 142 Chapter 10 Appendices Sel
110. face to allow morphs to render themselves on paper The graphics interface is implemented by canvas objects There may eventually be many kinds of canvases for ren dering onto displays of differing resolutions color properties or bit depths The current system provides four types of canvas WindowCanvas and pixmapCanvas draw onto a window or an offscreen buffer via the X protocol A NullCanvas has the same interface but does not actually draw anything it can be used to factor out the cost of graph ics during performance analysis ColorRecordingCanvas is used internally by the colormap manager All canvases implement the following messages for drawing geometric shapes draw a single pixel point p Color c outline or fill a rectangle or fill the entire canvas rectangle r Color c rectangle r Width w Color c fillRectangle r Color c filiCcolor draw a solid or dashed line or a connected sequence of line segments line ptl To pt2 Color g line ptl To pt2 Width w Color c dashedLine pt1 To pt2 DashSize d Offset o Color c dashedLine pt1 To pt2 Width w DashSize d Offset o Color c lines pointList Color c lines pointList Width w Color c outline or fill a polygon polygon pointList Color c polygon pointList Width w Color c fillPolygon pointList Color g outline or fill a circle circleCenteredAt pt Diameter d Color c circleCenteredAt pt Diameter d Width w Color c fillCircleCentere
111. fier regular object keyword slot small keyword cap keyword regular object small keyword identifier cap keyword identifier regular object slot name identifier parent name parent name gt identifier 10 4 Built in types There are a small number of built in types that are directly supported through primitives and syntax Integers and floats are provided with primitives for performing arithmetic operations comparisons etc Strings have a byte vector part for storing the characters Special string primitives are provided Blocks are objects which combine code with an environment link Used for control structures they are described in section 2 1 7 In addition there are a number of VM supported types described in the sections on the Self World and the VM reference manual such as mirrors processes vectors proxies and profilers 10 5 Useful Selectors This is a list of selectors which Selfers should find useful as a starting point Copying 138 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 compare IfLess Equal Greater compare IfLess Equal Greater Incomparable clone shallow copy for use within an object clients should use copy copy copy the receiver possibly with embedded copies or initialization Comparing Equality equal l not equal hash hash value identical the same object this is reflective
112. formation to name objects among other things Note that the title of the prototype on the left has already been updated to reflect its new name 90 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 other prototypes not to clones of those objects instances The system can be told to maintain the copied down slots of the ovalMorph prototype automatically by setting its copy down parent Figure 10 Select the Show Annotation command in the middle button menu on the title of the ovalMorph s outliner Set the copy down parent field to morph the copy down selector to copyRemoveAll Morphs and press the green top button to accept this change The copy down selector is sent to the copy down parent to create a fresh copy from which to copy slots The system will ask if the slots parent and prototype should be omitted from the copy down operation since their contents differ from that of that of the copy down parent They should be Finally it would be nice to be able to save the prototype and traits for the new ovalMorph in a file so that it can be archived or read into another Self world Several steps are required First the module itself must be created The system will create a new module after getting confirmation from the user the first time its name is used Then the slots in the globals and traits namespace object must be assigned to the ne
113. g copySize FillingWith 4 5 Substituting Values for Blocks 43 Self Handbook Documentation Release 2 for Self 4 4 4 7 Hash and Sets and dictionaries are implemented using hash tables In order for an object to be eligible for inclusion in a set or used as a key in a dictionary it must implement both and hash hash maps an object to a smal11Int Further hash must be implemented in such a way that for objects a and b a b implies a hash b hash The behavior that sets disallow duplicates and dictionaries disallow multiple entries with the same key is dependent upon the correct implementation of hash for their elements and keys Finally the implementation of sets and dictionaries will only work if the hash value of the objects in the set do not change while the objects are in the set dictionary This may complicate managing sets of mutable objects since if the hash value depends on the mutable state the objects can not be allowed to mutate while in the set Of course a trivial hash function would simply return a constant regardless of the contents of the object However for good hash table performance the hash function should map different objects to different values ideally distributing possible object values as uniformly as possible across the range of small integers 4 8 Equality Identity and Indistinguishability Equality identity and indistinguishability are three related concepts that are often confus
114. g compiled methods with their associated debugging and dependency information The bar la belled code represents the cache containing the actual machine code for methods including some headers and relocation information it is divided into code generated by the primary non inlining compiler or NIC and code generated by the secondary smarter compiler SIC The cache represented by the bar labelled deps contains dependency infor mation for the compiled methods and the cache represented by the bar labelled debug contains the debugging information The three way split reduces the working set size of the code cache The cache repre sented by the bar labelled PICs contains polymorphic inline caches Color Meaning black Allocated residing in real memory gray Allocated paged out white Unallocated memory 10 8 Primitives Primitives are Self methods implemented by the virtual machine The first character of a primitive s selector is an underscore _ You cannot define primitives yourself unless you modify the Virtual Machine nor can you define slots beginning with an underscore 148 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 10 8 1 Primitive failures Every primitive call can take an optional argument defining how errors should be handled for this call To do this the primitive is extended with an IfFail argument For example _AsObject become
115. ges postRead slot to evaluate after reading a snapshot 10 6 Every Menu Item in the Programming Environment This table only covers the middle button menus the right button morph menu is described elsewhere It merges items from several menus the background menu the outliner whole object menu the outliner category menu the outliner slot menu the text editor menu the debugger stack menu the iterator object menus and the changed module morph menu Table 7 Menu Items Label Function Add Category Adds a category to an object or category Add Slot Adds a slot to an object or category Added or Changed Slots On a module morph enumerates slots added changed since last save All Modules Summons a hierarchical list of all modules from the changed modules morph Continued on next page 144 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 Table 10 2 continued from previous page All Slots Changed Modules Children Clean Up Clean Up Memory Collapse All Copy Down Children Copy Down Parent Copy Core Sampler Create Button Cut Do Selection Do it Edit Evaluator Expand All Expatriate Slots Don t Filter Frames Find Slot Find Slot of Flush Forget I was changed Get Module Object Get Selection Get it Hide Annotation Hide Comment Implementors Implementors of Load Morph From File Make Creator Make Private Make Public Make Unde
116. gnable slot x show all senders of x i e methods that might assign to x in the selected object its ancestors and it descendants Sets the module of a slot or group of slots Summons an outliner on the shell Used for evaluating expressions On a debugger stack disable filtering Shows the object or slot annotation Shows the object or slot comment For morph object outliners summons the morph that the object imple ments Appears on the object menu Automates several steps equivalent to sub classing in Smalltalk Creates a copy down child of the selected object and makes a new parent object for the new child that inherits from the selected object s parents It also sets some of the annotations for transport Pins up the menu Toggles an X Window spying on the Virtual Machine A nice source of reassurance Show an inheritance hierarchy textually Only works on certain objects on alternate Thursdays Saves all the objects in the Self world to a fairly large file 10 7 The system monitor The Self system contains a system monitor to display information about the internal workings of the system such as memory management and compilation It is invoked with _Spy true there is are shortcuts in the shell seyOn and spyOff When it is active the system monitor takes over a portion of your screen with a window that looks like this 146 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 co Uy
117. hat allows blocks to ignore extra arguments behavior that allows an object to behave like a block that evaluates to that object this permits a non block object to be passed to a method that expects a block behavior that allows an object to be its own key in a collection key default behavior for doubly dispatched messages behavior for printing error messages and stack dumps error and halt It is important to note that not all objects in the system inherit this default behavior It is entirely permissible to construct objects that do not inherit from the lobby and the Self world contains quite a few such objects For example the objects used to break a namespace into separate categories typically do not inherit from the lobby Any program intended to operate on arbitrary objects such as a debugger must therefore assume that the objects it manipulates do not understand even the messages in defaultBehavior Modules defaultBehavior errorHandling 24 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 3 2 2 The Root Traits Traits Clonable and Traits Oddball Most concrete objects in the Self world are descendants of one of two top level traits objects traits clonable and traits oddball The distinction between the two is based on whether or not the object is unique For example true is a unique object There is only one true object in the entire system although there are many references to it On th
118. hat transport out with type specific creation strings e Finally if it can do nothing else the transporter creates a new object for the contents of the slot The object is created in a clever way so that a file that adds slots to an object can be read before the file that officially creates the object without loss of information 8 The Self Virtual Machine provides for annotations on slots or whole objects While the annotations do not influence program execution they can be accessed and modified by Self s reflective facility mirrors Annotations are used to hold many things including comments on objects and slots 9 isComplete is used by the environment to decide when it is safe to send messages like printString 5 4 The Transporter 69 Self Handbook Documentation Release 2 for Self 4 4 How the transporter files out objects Is slot annotated with Write O an initializer that expression expression yes Is slot contents complete and islmmutableForFilingOut Does slot contents have valid creator Is this slot no the creator Refer to the creator no yes Is slot contents complete Send storeStringNeeds storeString fFail toreString yes suceess no yes failure does not exist yet 70 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 Filing out objects is too complicated and over the past two years we have r
119. he empty vertical bar notation to create an empty object note that the parser currently requires a space between the vertical bars Self Handbook Documentation Release 2 for Self 4 4 Block objects are written like other objects except that square brackets and are used in place of parentheses slotl slot2 here is some code in a block printLine A slot list consists of a possibly empty sequence of slot descriptors 2 2 separated by periods A period at the end of the slot list is optional The code for an object is a sequence of expressions 2 3 separated by periods A trailing period is optional Each expression consists of a series of message sends and literals The last expression in the code for an object may be preceded by the operator 2 1 8 2 1 2 Data objects Data objects are objects without code Data objects can have any number of slots For example the object has no slots i e it s empty while the object x 17 y 18 has two slots x and y _ x 17 slots _ m y 18 A data object returns itself when evaluated 2 1 3 The assignment primitive A slot containing the assignment primitive is called an assignment slot 2 2 2 When an assignment slot is evaluated the argument to the message is stored in the corresponding data slot 2 2 in the same object the slot whose name is the assignment slot s name minus the trailing colon and the receiver 2 3 i
120. he lobby The lobby is also the sending method holder for any sends in the initializing expression Nil is the object used to initialize slots without explicit initializers It is intended to indicate not a useful object This object is provided by the Self implementation 136 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 10 2 Lexical overview small letter cap letter letter identifier small keyword cap keyword argument name op char operator number integer real fixed point float general digit decimal base string normal char escape char numeric escape comment comment char dede dle de Je loa lalo dde odo deca ales ok dedo ale e e cle a al bl 1b 62 IB LZ small letter cap letter small letter _ letter digit _ identifier cap letter letter digit _ identifier VPL UPLB OTM Lor Le Le Le Le LPP le le ly by bP rey op char op char Gnteger real base general digit general digit fixed point float decimal decimal decimal decimal e E decimal digit letter digit digit decimal r R normal char escape char any character except V and Av 1 Nb 1 An AP 1 Ar Av Age 130141 19 9 199 numeric escape Ax general digit general digit Ad No digit digit digit 2 comment ch
121. he name space distinct For example the traits slot of the lobby is not a parent slot This allows a convention that gives prototypes and their associated traits objects similar names a prototype and its associated traits object have the same local name but the prototype is placed in a slot in the globals object whereas the traits of the prototype is placed in a slot in the traits object Since the traits slot of the lobby is not a parent slot the name of the traits object must start with the prefix traits The globals slot on the other hand is a parent slot so the name of a prototype object needs no prefix Thus list refers to the prototype list while traits list refers to its traits object for lists As a matter of style programs should refer to objects by the shortest possible name This makes it easier to re organize the global namespace as the system evolves If programs used full path names then many more names would have to be updated to reflect changes to the namespace organization a tedious chore 3 2 The Roots of Behavior 3 2 1 Default Behavior Certain common behavior is shared by nearly all objects in the Self world This basic behavior is defined in the defaultBehavior slot of the lobby and includes e identity comparisons and inequality default behavior for printing reimplement printString in descendants mirror creation reflect support for point and list construction and amp behavior t
122. he outliner to be affected For example anExampleObject has many regions and here are some of them Click on the desired part of the object be it object category slot text editor or annotation annotations will be explained later The Evaluator Try out the whoAmI method Push the E button in the top right of the outliner The receiver of any messages sent from an evaluator or indeed any text editor via Do It andGet It in the editor s middle button menu in an object outliner is the object itself Type whoAmI into the evaluator and hit the Get it button or select the Get It from the text editor menu to send the message and get back the result Move the result out of the way and left click to set it down Adding a slot Try one more change adding a slot to the category a category of slots Hold the cursor over the words a category of slotsand select Add Slot from the middle button menu After selecting Add Slot a space for a new slot will appear in the object Each line shows the syntax for a different kind of slot Create a simple variable by typing me lt Gumby and hitting the green button to accept the change 2 However in a stack frame in the debugger described below the receiver of a message is the same as the receiver for the stack frame 3 Tam revising this for Self 4 1 on my trusty Mac and Self does not implement environment variables here 4 Since all that stuff in the text editor was i
123. he period and the message name Examples resend display resend 5 resend min 17 Max 23 A directed resend constrains the resend through a specified parent It is written similar to a normal resend but replaces resend with the name of the parent slot through which the resend is directed Examples listParent height intParent min 17 Max 23 Only implicit receiver messages may be delegated via a resend or a directed resend 2 3 6 Message lookup semantics This section describes the semantics of message lookups in Self In addition to an informal textual description the lookup semantics are presented in pseudo code using the following notation s name The name of slot s s contents The object contained in slot s s isParent True iff s is a parent slot s obj pred s The set of all slots of object obj that satisfy predicate pred ISI The cardinality of set S The message sending semantics are decomposed into the following functions send rec sel args The message send function 2 3 7 lookup obj rec sel V The lookup algorithm 2 3 8 undirected_resend The undirected message resend function 2 3 9 directed_resend The directed message resend function 2 3 9 eval rec M args The slot evaluation function as described informally throughout 2 1 2 3 7 Message send There are two kinds of message sends a primitive send has a selector beginning with an
124. he snapshot Since fatal errors usually arise from a bug in the virtual machine please send the Self group a bug report and include a copy of the error message if possible If the error is reproducible please describe how to reproduce it including a snapshot or source files may be helpful 8 11 The initial Self world The diagram on the following pages shows all objects in the bare Self world In addition literals like integers floats and strings are conceptually part of the initial Self world block and object literals are created by the programmer as needed All the objects in the system are created by adding slots to these objects or by cloning them Table 1 lists all 112 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 the initial objects and provides a short description for each Reading in the world rearranges the structure of the bare Self world see The Self World Table 1 Objects in the initial Self world Object lobby Description The center of the Self object hierarchy and the context in which expres sions typed in at the VM prompt read in via _RunScript or used as the initializers of slots are evaluated Objects in the lobby shell snapshotAction systemObjects After reading in the world shell is the context in which expressions typed in at the prompt are evaluated An object with slot for the startup action see section 5 2 postRead
125. he underlying graphics context executing the block provided which presumably issues some drawing commands to that canvas and restoring the original state of the graphics context Nested invocations of withClip Do are handled sensibly a stack of clipping rectangles is maintained and drawing operations are clipped to the intersection of all rectangles currently on the stack 7 12 1 Specifying Colors Colors in morphic are represented by paint objects A paint can be manipulated as either a red green blue triplet or as a hue saturation brightness triplet Red green blue saturation and brightness are specified as numbers in the range 0 0 1 0 where zero means black or unsaturated and one means full brightness or saturated Hue which corresponds to the angular location of the hue on the color wheel is specified as a number in the range 0 0 360 0 where zero corresponds to red Colors with zero saturation i e black white and shades of gray have no hue if you increase the saturation of such an achromatic color its hue is arbitrarily chosen to be zero red Paints provide transformations to change the red green or blue component change the hue saturation or brightness component and interpolate between two colors Since paint objects are immutable all these transformations are functional That is they return a new paint object leaving the original paint object unchanged Paint objects describe colors in a device independe
126. her than calling the primitive s wrapper method The sender can extract the various return values from the result object by name The second way is to pass in one block for each value to be returned For example countLines n lines n Words n words n Characters n characters n Each block simply stores its argument into the a local variable for later use The countLines Words Characters method would evaluate each block with the appropriate value to be returned countLines lb Words wb Characters cb lb value lineCount wb value wordCount 42 Chapter 4 A Guide to Programming Style Self Handbook Documentation Release 2 for Self 4 4 cb value charCount 4 5 Substituting Values for Blocks The lobby includes behavior for the block evaluation messages Thus any object that inherits from the lobby can be passed as a parameter to a method that expects a block the object behaves like a block that evaluates that object For example one may write x gt 0 ifTrue x False x negate rather than x gt 0 ifTrue x False x negate Note however that Self evaluates all arguments before sending a message Thus in the first case x negate will be evaluated regardless of the value of x even though that argument will not be used if x is nonnegative In this case it doesn t matter but if x negate had side effects or if it were very expensive it would be bett
127. hod 7 One rough edge remaining in the Self user interface is the existence of two test editors and this one does not implement multi character selection sigh Or you could type control A to go the start and control K to delete the whole field sigh 5 2 Browsing Concepts 61 Self Handbook Documentation Release 2 for Self 4 4 4Process whoAml Lookup enor evnronmentAtlfFal not found Continue Step Step lexical Next Finish Frame Abort 4Stack bakos eynironmentAt arg LOGNAME ss IfFail arg tom El ejet whoAml ye os evnironmentAt LOGNAME IfFail The Phe Object whoAm El Less stack Changing a method in an object outliner vs in a debugger Object Outliner before change old method Debugger before change object 1 object 2 debugger Debugger after change Object Outliner after changing object 2 old method new method 62 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4 Process whoAml Status suspended Continue Step Step lexical Next Finish Frame Abort 4Stack ajet whoAml PHI os environmentAt LOGNAMF IfFail The Phe AChbject whoAm El Less stack 4 Process whoAml Status suspended Continue Step Step lexical Next Finish Frame Abort 4 Stack bakos environmentAt t0 LOGNAME fFail fb tom a fb value unimplemented_on_Mac Ajet whoAm B os environ
128. how to create a new kind of first class morph using each of these approaches 7 3 2 Morph Creation The Bottom up Approach In the bottom up approach one is initially interested in getting a morph with the desired behavior as quickly as possible Thus an appropriate morph is copied and modified by adding slots directly to the morph itself Suppose one wished to create a morph that displayed as an oval and that toggled between two colors when the middle mouse button was pressed To get a morph to modify evaluate morph copy This will make an outliner on a new morph Use the Show Morph command on this outliner s middle button menu to make the graphic representation of the copy appear The Add Slot command on the outliner s middle button menu can be used to add a data slot to hold the alternate color Enter the following expression and accept it by clicking on the green top button otherColor lt paint named leaf The morph s drawing behavior can be customized by adding the method baseDrawOn aCanvas aCanvas fillArcWithin baseBounds From 0 Spanning 360 Color color self Morphic optimizes shadow drawing for rectangular morphs such as prototypical morph which draws as simple rect angle However this morph is not rectangular To make its shadow reflect its true shape the isRectangular behavior must be overridden by adding the constant slot 84 Chapter 7 Morphic The Self User Interface Framework
129. iants that foreignFct objects rely on Relevant oddballs linker dynamic linker for current platform sunLinker dynamic linker implementation for SunOS Solaris foreignCodeDB registry for foreignCode objects Modules foreign 3 11 I O and Unix oddball unix clonable proxy unixFile mixes in traits unixFile currentOsVariant The oddball object unix provides access to selected Unix system calls The most common calls are the file operations creat open close read write lseek and unlink tcpConnectToHost Port IfFail opens a TCP connection The select call and the indirect system call are also supported taking a variable number of integer float or byte vector arguments the latter being passed as C pointers unixFile provides a higher level interface to the Unix file operations The oddball object tty implements terminal control facilities such as cursor positioning and highlighting Relevant oddballs stdin stdout stderr standard Unix streams tty console terminal capabilities Modules unix stdin tty ttySupport termcap 3 12 Other Objects Here are some interesting oddball objects not discussed elsewhere 34 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 comparator an object that can compute diffs between sequences compilerProfiling compiler profiling desktop The controlling object for the graphical user interface his
130. ically starts with a copy of some existing morph and adds or overrides state and behavior to create the new morph Often the most appropriate starting point is a copy of morph the root of the morph object hierarchy Morph has default behavior for everything from drawing to handling user inputs one thus starts with a working morph and modifies its behavior incrementally to create the new type of morph The programming aspect of creating a new morph is straightforward However four other things must be done to make the new morph into a first class citizen First its behavior should be factored into a shared parent called a traits object to allow the behavior of all instances to be changed by changing the shared parent Second the shared traits object and a prototypical instance of the new morph should be embedded in the global namespace Third the copy down parent of the prototype should be set so that changes to the structure of the parent are propagated correctly Finally the new prototype and traits objects should be assigned to a module to allow the code for the new morph to be saved in a file Of course if one just wants to do a quick experiment none of these housekeeping chores are necessary However sometimes one decides to make an experimental morph into a first class morph the bottom up approach In other cases one sets out from the beginning to create a new first class morph the top down approach The next two sections will describe
131. if any If it is important to avoid this transient state one can move the each slot by first copying it from the prototype into the parent and then remove it from the prototype A slot is removed simply by moving it and dropping it onto the trash can morph or by dropping it on the background and then dismissing it 4 an object lt 8 type morph 4an object lt 370 gt Modules morph morphSaving Module parent an ob pore Ao arias Sis morph middlekiouselown evt a otherColor g powmie35 gt lean qa biasi Mor ph Site isRectangular jale bing ote parentk traits morph la Evaluate Dismiss Figure 7 6 Figure 6 Using slot dragging to move a slot into the new traits object Using direct manipulation to move and copy slots makes programming feel like manipulating concrete objects This narrows the gap between composition of graphical objects building and modifying composite morphs and programming Now changing the traits object changes the behavior of all instances For example the draw method in the traits can be changed to draw an unfilled oval To demonstrate the power of shared behavior first make several copies of the protypical oval using the Duplicate command on its right mouse menu Then modify the baseDrawOn method in the shared traits as follows note the change from fillArcWithin to just arcWithin baseDrawOn aCanvas aCanvas arcWithin baseBounds indent 3 From 0 Spanning 3
132. ifferent owners it is necessary to use their positions in the world s coordinate system which are computed by sending the globalPosition message to each morph 7 9 2 Synchronization Animation stepping and other activities are handled synchronously as part of the basic user interface loop Thus a sequence of actions done by an activity or a step method appear to happen atomically the user never sees the morph in an intermediate state in which some but not all of the actions have taken place For example if a morph is removed from one morph and added to another the user never sees the transient state in which the morph is not in the world at all Likewise any layout modifications resulting from user actions such as adding a new morph to a row appear to happen atomically one never sees a partially complete layout Often however an independent Self thread wishes to manipulate morphs in the user interface In order to make such actions appear atomic they should be done under the protection of the UI synchronization semaphore The preferred way to do this is to wrap the action or actions in a block to be executed between display cycles of the morph s world aMorph safelyDo Synchronization errors usually appear as intermittent graphical glitches although in rare cases the submorph structure may be corrupted e g a morph appearing in the submorph lists of multiple morphs 7 9 3 Display Updating Morphic uses a double buff
133. in the snapshot If the code in a snapshot is for some reason corrupted but the objects are not this option can be used to recover the snapshot 1 logfile Writes a log of events generated by the spy to logfile r Disables real timer interrupts t Disables all timers Other command line options are ignored by the Virtual Machine but are available at Self level via the primitive _CommandLine 8 2 System triggered messages Certain events cause the system to automatically send a message to the lobby After reading a snapshot the expression snapshotAction postReadis evaluated This allows the Self world to reinitialize itself for example to reopen windows There are other situations in which the system sends messages see section 5 3 8 3 Run time message lookup errors If an error occurs during a message send the system sends a message to the receiver of the message Any ob ject can handle these errors by defining or inheriting a slot with the corresponding selector All messages sent by the system in response to a message lookup error have the same arguments The first argument is the offending 109 Self Handbook Documentation Release 2 for Self 4 4 message s selector the additional arguments specify the message send type one of normal implicitSelf undirectedResend directedResend or delegated the directed resend parent name or the delega tee 0 if not applicable the sendi
134. in the ui2 system Now here comes the nice part the Self environment incrementally maintains a mapping from modules to slots and a list of changed modules which can be obtained from the background menu When you make a change the appropriate module will be added to the list and can be written as a source file by clicking its w button The middle button menu on the changed modules and individual modules contains a host of useful entries for understanding what has been changed 5 4 5 What to Save for the Contents of a Slot At this point the reader may be thinking So modules know which slots they include but how do they know which objects to include After all when the transporter saves a slot in a file what can it put for the contents of the slot Here is where the transporter runs smack into the problem of not enough information and a variety of means have to be used As shown in the flowchart below e Sometimes the programmer does not want to store the actual contents of a slot but instead wants to store an initialization expression This intention is captured with another annotation on a slot each slot can either be annotated Follow Slot or Initialize To Expression In the latter case an initializer is also supplied e Even though the transporter is supposed to follow the slot it may contain an object that is created by another slot For example the parent slot in a point should just refer to traits point rather than recreating
135. ing block if key is absent addFirst add element to head of list addLast add element to tail of list copyAddAll return a copy containing the elements of both receiver and argument copyContaining return a copy containing only the elements of the argument Removing remove remove the given element remove IfAbsent remove the given element evaluating block if absent removeAll remove all elements removeFirst remove first element from list removeLast remove last element from list removeAllOccurences remove all occurrences of this element from list removeKey remove element at the given key removeKey IfAbsent remove element at the given key evaluating block if absent copyRemoveAll return an empty copy Accessing 10 5 Useful Selectors 141 Self Handbook Documentation Release 2 for Self 4 4 first last includes occurrencesOf findFirst IfPresent IfAbsent return the first element return the last element test if element is member of the collection return number of occurences of element in collection evaluate present block on first element found satisfying criteria absent block if no such element at return element at the given key at IfAbsent return element at the given key evaluating block if absent includesKey test if collection contains a given key Iterating do iterate passing each element to argument block doFirst Middle Last IfEmpty doFirst MiddleLast IfEmpty doFirstLast Middle I
136. ing yields exactly the same object as above arg clone x x arg x y y arg y The slot above is a binary slot 2 3 2 taking one argument and having a name that consists of operator symbols Slots like x or y in a point object are unary slots 2 3 1 which take no arguments and have simple identifiers for names In addition there are keyword slots 2 3 3 which handle messages that require one or more arguments A keyword slot name is a sequence of identifiers each followed by a colon The arguments in keyword methods are handled analogously to those in binary methods each colon terminated iden tifier in a keyword slot name requires a corresponding argument slot in the keyword method object and the argument slots may be specified either all in the method or all interspersed with the selector parts For example ifTrue False trueBlock falseBlock trueBlock value and ifTrue trueBlock False falseBlock trueBlock value produce identical objects 2 2 4 Parent slots A unary slot name followed by an asterisk denotes a parent slot The trailing asterisk is not part of the slot name and is ignored when matching the name against a message Except for their special meaning during the message lookup process 2 3 8 parent slots are exactly like normal unary slots in particular they may be assignable allowing dynamic inheritance Argument slots cannot be parent slots
137. ion can be defined in two ways Frame based animation lets the programmer control animation smoothness by specifying that the animation should take a given number of frames regardless of the time per frame Time based animation lets the programmer specify the desired amount of time the animation should take but the number of intermediate frames depends on the time per frame which may vary with system load scene complexity and other factors Animations can be paced linearly or slow in slow out A slow in slow out animation starts slowly builds to a maximum pace then decelerates There are activities that animate the position size and color of morphs activities that send arbitrary messages and compound activities that combine a set of other activities either sequentially or concurrently In fact this activity architecture is the basis of all animation in Morphic an activity called a periodicStepActivity is used to implement the stepping facility 100 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 7 9 Other Issues 7 9 1 Local versus Global Coordinates The position of a morph is defined relative to the position of its owner This makes it unnecessary to update the positions of all the submorphs when moving a composite morph However it also means that morphs with different owners have positions in different coordinate systems In order to compare the positions of morphs having d
138. ion explicit when it is necessary 4 2 Objects Have Many Roles Objects in Self have many roles Primarily of course they are the elements of data and behavior in programs But objects are also used to factor out shared behavior to represent unique objects to organize objects and behavior and to implement elegant control structures Each of these uses are described below 4 2 1 Shared Behavior Sometimes a set of objects should have the same behavior for a set of messages The slots defining this shared behavior could be replicated in each object but this makes it difficult to ensure the objects continue to share the behavior as the program evolves since the programmer must remember to apply the same changes to all the objects sharing the behavior Factoring out the shared behavior into a separate object allows the programmer to change the behavior of the entire set of objects simply by changing the one object that implements the shared behavior The objects that share the behavior inherit it via parent slots containing references to the shared behavior object By convention two kinds of objects are used to hold shared behavior traits and mixins A traits object typically has a chain of ancestors rooted in the lobby A mixin object typically has no parents and is meant to be used as an additional parent for some object that already inherits from the lobby 4 2 2 One of a kind Objects Oddballs Some objects such as the object t rue are
139. ions may not be separated by whitespace 1 e there may not be whitespace within a lexical token Tokens are formed from the longest sequence of characters possible Whitespace may separate any two tokens and must separate tokens that would be treated as one token otherwise 2 4 1 Character set Self programs are written using the following characters e Letters The fifty two upper and lower case letters ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghi jkImnopqrstuvwxyz e Digits The ten numeric digits 0123456789 e Whitespace The formatting characters space horizontal tab ASCII HT newline NL carriage return CR vertical tab VT backspace BS and form feed FF Comments are also treated as whitespace e Graphic characters The 32 non alphanumeric characters 1 amp _ l 3 lt gt 2 4 2 Identifiers An identifier is a sequence of letters digits and underscores _ beginning with a lowercase letter or an underscore Case is significant apoint is not the same as aPoint Productions small letter gt a I 1 z cap letter gt IB II letter small letter cap letter identifier small letter _ letter digit _ Examples i _IntAdd cloud9 m a_point The two identifiers self and resend are reserved Identifiers beginning with underscores are reserved for primitives 2 4 3 Keywords Keywords are used as slot names and as message names
140. ions some of the most useful and reusable morphs To find out more about a given morph use the programming environment to examine its prototype and traits objects Useful comments are sometimes buried in the bodies of methods Widget morphs are interactive allowing the user to invoke an action or input some data sliderMorph Allows the user to specify a numerical value in some range When the slider is manipulated 1ts target object is sent a user specified message with the new slider value as an argument ui2Button Executes a user specified script when the button is pressed The script can refer to the button s target The target of a button or slider morph can be set by using the middle mouse menu Set Target command This sets the target slot of the button or slider to the morph directly below it Buttons are often decorated with a textual label but a button can contain arbitrary morphs instead of or in addition to this label ui2Menu A column full of buttons A menu can be pinned down using the unlabeled button at its top It can then be manipulated or disassembled like any other morph Menus support a rich set of messages for adding normal or grayed out buttons and for inserting dividing lines Structural morphs are typically used to bind morphs together and arrange them into a pleasing layout rowMorph and columnMorph Pack their submorphs into a row or column These morphs offer several justification options and can also pro
141. is also an expression that can be evaluated in the context of the lobby to produce the object Because globals is a parent slots it can be omitted from this path name expression Doing this yields the short path name list Not all objects have path names only those that can be reached from the lobby Such objects are called well known 4 3 1 How objects are printed When an expression is typed at the prompt it is evaluated to produce a result object The prompt then creates a mirror on this result object and asks the mirror to produce a name for the object A mirror is used because naming is reflective The object s creator path annotation provides a hint about the path from the lobby to either the object itself or its prototype If the object is a clone a or an is prepended to its prototype s creator path In addition to its path the mirror also tries to compute a printString for the object if it is annotated as isComplete Then the two pieces of information are merged For example the name of the prototype list is list but the name of list copy add 17 is a list 17 See the naming category in mirror traits for the details of this process 4 3 2 How to make an object print The distinction between objects that hold shared behavior traits and mixin objects and concrete objects prototypes copies of prototypes and oddballs is purely a matter of convention the Self language makes no such distinction
142. is difficult to tell when printString is likely to fail Using reflection the facility can avoid sending print String to objects that do not define printString But that is not the case with traits point The solution taken in this version of the system is to mark printable objects with a special annotation The printing facility sends print String to the object only if the object contains an annotation IsComplete The existence of an isComplete annotation in an object means that the object is prepared to print itself The object agrees to provide behavior for a variety of messages see the programming environment manual for more details 4 4 How to Return Multiple Values Sometimes it is natural to think of a method as returning several values even though Self only allows a method to return a single object There are two ways to simulate methods that return multiple values The first way is to use an inlined object For example the object p lobby lines words characters could be used to package the results of a text processing method into a single result object count r px lobby lines words characters Ei E Gopy lines 1Count r words wCount r characters cCount K r Note that the inline object prototype inherits copy from the lobby If one omitted its parent slot p one would have to send it the _Clone primitive to copy it It is considered bad style however to send a primitive directly rat
143. is even true if receiver is odd amp E amp II AN complement lt lt gt gt lt gt and or xor bitwise complement logical left shift logical right shift arithmetic left shift arithmetic right shift Logical operations booleans amp E amp and II or My xor not logical complement Constructing point construction receiver and argument are integers rectangle construction receiver and argument are points HH rectangle construction receiver is a point argument is an extent amp collection construction result can be converted into collection 4 concatenation Printing print print object on stdout printLine print object on stdout with trailing newline printString return a string label printStringDepth return a string label with depth limitation request printStringSize return a string label with number of characters limitation request printStringSize Depth return a string label with depth and size limitation request Control Block evaluation value With evaluate a block passing arguments Selection ifTrue evaluate argument if receiver is true ifFalse evaluate argument if receiver is false ifTrue False ifFalse True evaluate first arg if true second arg if false evaluate first arg if false second arg if true Local exiting exit exit block and return nil if block s argument is evaluated exit Value exit block and return a
144. it implementorsOf Limit sendersOf Limit returns a vector of mirrors on all objects in the system up to the limit returns a vector of mirrors on all objects referring to arg up to the limit returns a vector of mirrors on all objects referring to argument s re flectee up to the limit allows one to find references to a method returns a vector of mirrors on all objects with a parent slot referring to the given object up to the limit returns a vector of mirrors on objects with slots whose names match the given selector up to the limit returns a vector of mirrors on methods whose selectors match the given selector up to the limit Debugging halt halt the current process halt halt and print a message string error halt print an error message and display the stack warning beep print a warning message and continue Virtual Machine Generated Errors 78 Chapter 6 Useful Selectors Self Handbook Documentation Release 2 for Self 4 4 undefinedSelector Type Delega tee MethodHolder Arguments ambiguousSelector Type Delega tee MethodHolder Arguments missingParentSelector Type Del egatee MethodHolder Argu ments performTypeErrorSelector Type Delegatee MethodHolder Argu ments mismatchedArgumentCountSelector Type Delegatee MethodHolder Arguments primitiveFailedError Name lookup found no matching slot lookup found more than one matching slot parent
145. ivate and unspeci fied slots This distinction carries no semantics but serves to record the programmer s intentions 66 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 Add a comment to an object or slot Adding a Comment Show Comment in the object or slot middle menu to open up a com ment text editor then typing in the comment then hit the green button to accept it If an object or slot already has a comment it can be shown hidden by hitting the small button labeled with a single quote To amuse and intrigue those who follow Change creator annotation of an ob ject Set creator of contents of a slot to that slot Change copy down information Change the object s isComplete flag Annotating an Object Show Annotation in object mid dle menu to expose object annota tion information then click on cre ator path field and typing in desired creator path then hit green button to accept annotation Set Creator in slot middle menu Show Annotation in object mid dle menu to expose object anno tation information then click on copy down parent field and type in desired copy down path copy down selector and slots to omit then hit green button to accept an notation Show Annotation in object mid dle menu to expose object annota tion information then push one of the isComplete radio buttons then hit green bu
146. iver of the message smh the sending method holder sel the message selector args the actual arguments Output res the result object Algorithm M parent_lookup smh sel do the lookup case M 0 error message not understood M 1 res eval rec M args see 2 1 M gt 1 error ambiguous message send end return res 2 3 10 Directed Resend A directed resend looks only in one slot in the sending method holder The function directed_resend rec smh del sel args is defined as follows Input rec the receiver of the message smh the sending method holder del the name of the delegatee sel the message selector args the actual arguments Output res the result object Algorithm D s smh s name del find delegatee if D 0 then error missing delegatee one or none M lookup smh del sel do the lookup case M 0 error message not understood M 1 res val rec M args see 2 1 M gt 1 error ambiguous message send end return res 18 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 2 4 Lexical elements This chapter describes the lexical structure of Self programs how sequences of characters in Self source code are grouped into lexical tokens In contrast to syntactic elements described by productions in the rest of this document the elements of lexical EBNF product
147. ization based on a simple linear congruence algorithm For convenience the prototype for randomLC is random not randomLC Modules random 3 4 2 Time clonable time A time object represents a date and time to the nearest millisecond since midnight GMT on January 1 1970 The message current returns a new time object containing the current time Two times can be compared using the standard comparison operators One time can be subtracted from another to produce a value in milliseconds An offset in milliseconds can be added or subtracted from a time object to produce a new time object However it is an error to add two time objects together Modules time 3 5 Collections clonable collection collection hierarchy Collections are containers that hold zero or more other objects In Self collections behave as if they have a key associated with each value in the collection Collections without an obvious key such as lists use each element as both key and value Iterations over collections always pass both the value and the key of each element in that order to the iteration block Since Self blocks ignore extra arguments this allows applications that don t care about keys to simply provide a block that takes only one argument 28 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 Collections have a rich protocol Additions are made with at Put or with add or addA11 for implicitl
148. kstation Using an obsolete reference i e memory address would be disastrous Thus Self encapsulates such references within the special objects proxy for data references and fctProxy for function references Such objects are known collectively as proxies A proxy object bundles some extra information along with the memory address of the referenced object and uses this extra information to detect with high probability any attempt to use an obsolete proxy An obsolete proxy is called a dead proxy To make it possible to rapidly develop foreign code the virtual machine supports dynamic linking of this code This makes it unnecessary to rebuild the virtual machine each time a small change is made to the foreign code Dynamic linking facilities vary from platform to platform but the Self interface to the linking facilities is largely system inde pendent The SunOS Solaris dynamic link interface is defined in the sunLinker object However clients should always refer to the dynamic linking facilities by the name 1inker which will be initialized to point to the dynamic linker interface appropriate for the current platform The linker proxy and fctP roxy objects are rather low level and have only limited functionality For example a fctProxy does not know which code file it is dependent on The objects foreignFct and foreignCode establish a higher level and easier to use interface A foreign Code object represents an object file a file with
149. l floats have the same parent see 0 0 parent below All floats share this parent the float traits object In addition to a byte vector part a canonical string has one slot parent a parent slot containing the same object for all canonical strings see parent below All canonical strings share this parent the string traits object Blocks have two slots parent a parent slot containing the same object for all blocks see parent below and value or value or value With etc depending on the number of arguments the block takes which con tains the block s deferred method All blocks share this parent the block traits object Prototypical mirrors gt 8 11 The initial Self world 113 Self Handbook Documentation Release 2 for Self 4 4 snapshotAction lobby snapshotAction postRead E nil sr shat eC G oy systemObjects nil E perone j tty me tue s porone j gt bby wor E se COC e H Poy objVector objVector parent COIE reer parent H woy CCE m mee pr CEN CE CO pos 2 e e G w byteVectorMirror E z pe poet Gae G ty assignmentMirror smiMirror mirrorMirror pr TO CONO blockMirror CO floatMirror blockMeth Mirror E ww o methodAct Mirror reads 00 blockMe A Mirror orcos objectAnnotation E profiler Mirror ZOME e Fo w CC fctProxyMirror slotsMirror Figure 8 1 Figure 3 The initial Self world part 1 1
150. l kind of object containing a sequence of statements When a block is evaluated by being sent an acceptable value message its statements are executed in the context of the current activation of the method in which the block is declared This allows the statements in the block to access variables local to the block s enclosing method and any enclosing blocks in that method This set of variables comprises the lexical scope of the block It also means that within the block se1f refers to the receiver of the message that activated the method not to the block object itself A return statement in a block causes a return from the block s enclosing method See the Self Language Reference for a more thorough discussion of block semantics A block can take an arbitrary number of arguments and can have its own local variables as well as having access to the local variables of its enclosing method The statements in the block are executed when the block is sent a message of the form value With where the number of colons in the message is at least the same as the number of arguments the block takes extra arguments are ignored but it is an error to provide too few For example the following block takes two arguments sargi arg2 argl arg2 and can be evaluated by sending it the message value With to produce the sum of its arguments Blocks are used to implement all control structures in Self and allow the programmer to easily extend
151. le anUncategonzed Constant 3 14159 anUncategonzedMethod userQuery report Hella there anUncategonzed Vanable 17 4a category of slots aCategonzed Constant 3 14159 aCategonzedMethod wserQuery report Hello there aCategonzed Variable 17 4a subcategory whoAml Slots The little icons on the right edges of the slots reveal the type of slot a for a method slot a slot containing a method for a constant slot a slot containing a data object and foran assignable slot a pair of slots containing a data object and the assignment primitive In order to save space the data slot and its corresponding assignment slot are lumped together In other words in addition to the visible slot named aCategorizedVariable containing 17 there is another invisible slot named aCategorizedVariable containing the assignment primitive To look at the object contained in a data constant or assignable slot just click on its icon But if the slot is a method clicking its icon opens up a text editor on its source For example clicking on the icon at the right of the whoAmI box opens a text editor displaying its source and typing control L widens the object to show all the text in the selected window Text Editors The background of the editor is lighter than the outliner as a whole and this difference indicates that this editor is the current typing focus no matter where the mouse is you can type into this editor A left click on
152. le abstractString vector sequence sortedSequence 3 5 2 Strings Characters and Paragraphs collection byteVector string mutableString immutableString canonicalString A string is a vector whose elements are character objects There are three kinds of concrete string immutable strings mutable strings and canonical strings traits string defines the behavior shared by all strings A character is a string of length one that references itself in its sole indexable slot Mutable strings can be changed using the message at Put which takes a character argument or at PutByte which takes an integer argument An immutable string cannot be modified but sending it the copyMut able message returns a mutable string containing the same characters Canonical strings are registered in an table inside the virtual machine like Symbol objects in Smalltalk or atoms in LISP The VM guarantees that there is at most one canonical string for any given sequence of bytes so two canonical strings are equal have the same contents if and only if they are identical are the same object This allows efficient equality checks between canonical strings All message selectors and string literals are canonical strings and some primitives require canonical strings as arguments Sending canonicalize to any string returns the corresponding canonical string 3 5 Collections 29 Self Handbook Documentation Release 2 for Self 4 4 Character objects beh
153. le within the virtual machine containing a boolean integer or string in fact the option primitives can be thought of as primitive variables Invoking the version of the primitive that doesn t take an argument returns the current setting invoking it with an argument sets the variable to the new value and returns the old value Try running the system monitor with _Spy true The system monitor will continuously display various information about the system s activities and your memory usage The bracketed colon indicates that the argument is optional i e there are two versions of the primitive one taking an argument and one not taking an argument The bracket is not part of the primitive name See text for details 116 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 8 13 Interfacing with other languages This chapter describes how to access objects and call routines that are written in other languages than Self We will refer to such entities as foreign objects and foreign routines A typical use would be to make a function found in a C library accessible in Self Three steps are necessary to accomplish this e Write and compile a piece of glue code that specifies argument and result types for the foreign routine and how to convert between these types and Self objects e Link the resulting object code to the Self virtual machine e Create a function proxy object actually
154. lleciions 4 mor pas Peraphics ovalbmMorph an oh perce gt type mar ph 4 1 mor pls bar wiem ovalMorph az biz siem biz 4an object lt 8 type morph aan object lt 370 gt amp Modules morph morphSaving Module l parent an ob gered A gt parent trams morph otherColor a prite ojia 3 baseDrawOn aCanvas A ari Mor ph State isRectangular false Bb fling or middleMouseDown evt B Figure 7 8 Figure 8 Installing the new morph prototype and traits object in the globals and traits namespace objects In each case a new constant slot is created in the appropriate category then arrow dragging is used to make the new slot point to the desired object 7 3 Morph Traits and Prototypes 89 Self Handbook Documentation Release 2 for Self 4 4 E dit 4 globals 4 traits Copy 117 Modules 106 Mod Move bapplications slots Make private wi beollections boppicos Make public boraphics beollectio Show Comment 4 my mor phs beraphics Show Annotation ovalMorph oraiko phfsype mor ph 4 10 Set module Pes wien ovalM bake eu fl biz r yum Senders biz Implementors Find slot ovalMorph type morph pa Create button Modules morph morphoaving Muu parent an ob ec parent rats morph otherColor a paintc35 o leafl 3 IAE RA basi Mor ph State isRectangqular aie piling out middleMouseDown evt E Figure 7 9 Figure 9 Setting the creator slot of the new traits object The system uses this in
155. llows the lobby itself to be referred by name The lobby also has a number of other functions it is the location of the default behavior inherited by most objects in the system slot defaultBehavior 3 1 2 Names and Paths For convenience the lobby s namespace is broken into three pieces implemented as separate objects rooted at the lobby traits objects that encapsulate shared behavior Typically each prototype object has an associated traits object of the same name that describes the shared part of its behavior globals prototypical objects and one of a kind objects oddballs 23 Self Handbook Documentation Release 2 for Self 4 4 mixins small parentless bundles of behavior designed to be mixed into some other object Each of these namespace objects is categorized to aid navigation For example to find the parent of the prototype list object one could start with the globals slot of the lobby then get the 11 st slot of that object and then the parent slot of the list The sequence of slot names globals list parent is called a path and constitutes the list parent s full name Parent slots can be omitted from an object s full name since the slots in a parent are visible in the child via inheritance A path with parent slots omitted forms the short name for an object For example the short name for the list parent is simply list parent Non parent slots are used when it is desirable to keep a part of t
156. matching a pattern can be obtained thus primitives match _Memory Some points to note when browsing primitives e Since strings are special kinds of byte vectors primitives taking byte vectors as arguments can usually take strings The exception is that canonical strings cannot be passed to primitives that modify the object e Integer arithmetic primitives take integer receivers and arguments floating point arithmetic primitives take floating point receivers and arguments e All comparison primitives return either true or false Integer comparison primitives take integer receivers and arguments floating point comparison primitives take floating point receivers and arguments e The receiver of a mirror primitive must be a mirror unless otherwise noted 150 Chapter 10 Appendices
157. may be any expression such that receiver gt mname evaluates to a function e gfname is the name of the C function that the CC_mber_N macro expands into e fail_opt whether or not to pass a failure handle to the member function refer to section 5 13 6 for details e ci ai these are argument conversion pairs specifying how to obtain the arguments for the member function Any conversion pair found in Table 3 may be used 8 13 13 Conversion pairs A major function of glue code is to convert between Self objects and C C values This conversion is guarded by so called conversion pairs A conversion pair is a pair of arguments given to a glue macro It handles converting one or at most a few types of objects values There are different conversion pairs for converting from Self objects to C C values called argument conversion pairs and for converting from C C values to Self objects called result conversion pairs 8 13 14 Argument conversions from Self to C C An argument conversion is given a Self object and performs these actions to produce a corresponding C or C value e check that the Self object it has been given is among the allowed types If not report badTypeError invoke the failure block if present with the argument badTypeError e check that the object can be converted to a C C value without overflow or any other error If not report the relevant error e do the conversion i e construct
158. mentAt LOGNAME IfFail The Phi 20bjec whoAm E Less stack 5 2 Browsing Concepts 63 Self Handbook Documentation Release 2 for Self 4 4 This method is not too interesting especially on the Macintosh so leave the debugger by hitting Continue and letting the process finish Congratulations on making through the interactive tutorial In the remainder of this manual we will dive deeper into the programming environment for readers who want to write real programs in Self Here is more information on the debugger for future reference Table 2 The Debugger Buttons What it What it does says Continue Resumes running the process Step Perform one message send skipping over trivial accesses and assignments Steps into the called method Step Execute messages until control returns to the same lexical method or until this method Lexical exits Very useful for methods with blocks Next Performs a message send and any messages in the called method Steps over the called method Finish Finishes running the topmost method Frame Abort Kills off the process and dismisses the debugger In addition to the buttons each frame in the debugger has some items to control the process in its middle button menu Table 3 Process control items in the activation middle button menu What it says What it does Step Top frame same as step button not top frame Finish any called methods Next Same
159. n raise an exception that causes the IfFail block to be invoked at the Self level Make glue available by including it x include incls _glueDefs c incl Naive encryption function x char xencrypt char str int key void xFH static char res 1000 int i 120 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 if key 0 failure FH key 0 is identity map return NULL for i 0 str i itt res i str i key res i 0 return res x Make glue expand to full functions not just prototypes x define WHAT_GLUE FUNCTIONS C_func_2 string encrypt encrypt_glue fail string int undef WHAT_GLUE Observe that the fail_opt argument now has the value fail and that the encrypt function raises an exception using failure if the key is 0 There are two ways to raise exceptions extern C void failure void FH char x msg extern C void unix_failure void FH int err 1 In both cases the FH argument is the failure handle that was passed by the C_func_N macro The second argument to failure isa string It will be passed to the IfFail block in Self unix_failure takes an optional integer as its second argument If this integer has the value 1 or is missing the value of errno is used instead The integer is interpreted as a UNIX error number from which a corresponding string is constructed The string is then
160. n under construction The amp operator provides a concise syntax for constructing small collections For example 1 amp abc amp x asList constructs a list containing an integer a string and the object x A collector object is not itself a collection it is converted into one using a conversion message such as asList asVector or asString Modules collector 3 6 Pairs pair point rectangle traits pair describes the general behavior for pairs of arithmetic quantities A point is a pair of numbers rep resenting a location on the cartesian plane A rectangle is a pair of points representing the opposing corners of a rectangle whose sides are parallel with the x and y axes Modules pair point rectangle 3 6 Pairs 31 Self Handbook Documentation Release 2 for Self 4 4 3 7 Mirrors collection mirror mirrors smallInt mirrors float mirrors vectorish mirrors vector mirrors byteVector mirrors canonicalString mirrors mirror mirrors block mirrors method mirrors blockMethod mirrors activation liveOnes mirrors activation mirrors deadActivation mirrors methodActivation mirrors blockMethodActivation mirrors process mirrors assignment mirrors slots mirrors profiler Mirrors allow programs to examine and manipulate objects Mirrors get their name from the fact that a program can use a mirror to examine that is reflect upon itself A mirror on an object x is obtained by sending the message reflect x to
161. nation condition at the beginning of the loop proceed whileTrue quit whileFalse In each case the block that receives the message repeatedly evaluates itself and if the termination condition is not yet met evaluates the argument block The value returned by both loop expressions is nil It is also possible to put the termination test at the end of the loop ensuring that the loop body is executed at least once untilTrue quit untilFalse proceed Here is a loop that exits from the middle when quit becomes true exit quit ifTrue exit loopExit For the incurably curious the parameter to the user s block supplied by the LoopExit method is simply a block that does a return from the loopExit method Thus the loop terminates when exit value is evaluated The constructs loopExitValue exit and exitValue are implemented in a similar manner The value returned by the overall loopExit expression is nil Here is a loop expression that exits and evaluates to a value determined by the programmer when quit becomes true exit quit ifTrue exit value expr loopExitValue Module block 26 Chapter 3 The Self World Self Handbook Documentation Release 2 for Self 4 4 3 3 3 Block Exits It is sometimes convenient to exit a block early without executing its remaining statements The following constructs support this behavi
162. nce the most common operations that affect the layout of a morph such as adding and removing submorphs or changing its size take care of this already Normally layout is performed incrementally after every morph add or remove operation However when a large composite morph is to be constructed the cost of the repeated layout operations can be significant The program mer can ameliorate this problem by using the batch operation addAllMorphs rather than a sequence of individual addMorph operations If a morph is not in a worldMorph however all layout is deferred This is done partly to optimize creating large composite morphs which are often constructed off line and then added to the world and partly because the exact size of labelMorphs depends on font metrics that may vary from one X server to another Thus the layout of a morph containing labels would have to be recomputed in the context of a particular world anyway Occasionally one needs to know the exact size of a newly created morph for example to ensure that a menu does not pop up partially off the edge of the screen In such cases it may be necessary to temporarily add the morph to the world in some remote location such as 1000000 1000000 to force it to be laid out 7 9 5 Morph Copying When a composite morph is copied its entire submorph tree is traversed and copied to produce a duplicate with the same structure However simply copying the structure is not quite
163. nect to a well known port number on a given machine the function est ablishConnection does this 2 Send the command line arguments over the connection established in 1 the safeWrite call in main does this 3 Whi le there is more input and the Self process has not shut down the socket connection relay from stdin to the socket connection and from the socket connection to stdout the function relay does this 130 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 8 13 18 Outline of server The server is a Self program It is found in the file server self When the server is started the following happens 1 Create a socket bind a name to it and start listening 2 Loop accept a connection and fork a new process both step 1 and 2 are performed by the method server start The a Reads a line from the connection b Sets up a context with a slot stdio referring to the connection c Evaluates the line read in step a in this context d Closes the connection 8 13 19 Foreign functions and glue needed to implement server The server program needs to do a number of UNIX calls to create sockets and bind names to them etc The calls needed are socket bind listen accept and shutdown The first three of these are only called in a fixed sequence so to make things easier a small C function socket_bind_ listen that bundles them up in the right sequence has been written Th
164. ng method holder and a vector containing the arguments to the message if any undefinedSelector Type Delegatee MethodHolder Arguments The receiver does not understand the message no slot matching the selector can be found in the receiver or its an cestors ambiguousSelector Type Delegatee MethodHolder Arguments There is more than one slot matching the selector missingParentSelector Type Delegatee MethodHolder Arguments The parent slot through which the resend should have been directed was not found in the sending method holder mismatchedArgumentCountSelector Type Delegatee MethodHolder Arguments The number of arguments supplied to the _Perform primitive does not match the number of argu ments required by the selector performTypeErrorSelector Type Delegatee MethodHolder Arguments The first argument to the _Perform primitive the selector wasn t a canonical string These error messages are just like any other message Therefore it is possible that the object P causing the error which is being sent the appropriate error message does not understand the error message M either If this happens the system sends the first message undefinedSelector to the current process with the error message M as argument If this is not understood then the system suspends the process If the scheduler is running it is notified of the failure The system will also suspend a process if it runs out of stack space too much recursion
165. nitially selected your typing conveniently replaced it all 5 2 Browsing Concepts 51 Self Handbook Documentation Release 2 for Self 4 4 The whole object S55 OOOO GREER ERE RRS OSX SEEK 3 14159 user Query report Hello there E 17 3 SITAS A category LX 3 14159 ESV PIIVI LLL LIP DO RIDE POEA y single slot faCategonzed Vanable a subcategory UG COS A single slot SS RRO SQ The text editor SSS After releasing the green button it stays down to let you know that it is still working After a few seconds the slot 5 appears 5 2 3 Debugger Explore the Self debugger Start by scrambling the send to environmentVariable IfFail as if you had misspelled it Press the green button to accept the change then hit the Get it button This should break something In fact instead of the result of the message a Self debugger will materialize The debugger has a label to indicate which process ran aground a status indication shown in blue some buttons for controlling the process and a collapsed outliner for the stack Expand the stack The stack filters out uninteresting frames by default The debugger assumes that the first method you want to see is the one based on the text in the evaluator and since the stack grows upwards this oldest frame appears at the bottom It has no method name and contains the code whoAmI That method called whoAmI whose code is too long to show next to the slot
166. nt Stanford Uni versity March 1992 CU93 Bay Wei Chang and David Ungar Animation From Cartoons to the User Interface In UIST 93 Conference Proceedings 1993 DS84 L Peter Deutsch and Allan M Schiffman Efficient Implementation of the Smalltalk 80 System In Proceed ings of the 11th Annual ACM Symposium on the Principles of Programming Languages Salt Lake City UT 1984 GR83 Adele Goldberg and David Robson Smalltalk 80 The Language and Its Implementation Addison Wesley Reading MA 1983 133 Self Handbook Documentation Release 2 for Self 4 4 HCU91 Urs H lzle Craig Chambers and David Ungar Optimizing Dynamically Typed Object Oriented Program ming Languages with Polymorphic Inline Caches In ECOOP 91 Conference Proceedings Geneva Switzer land July 1991 Published as Springer Verlag LNCS 512 1991 HCU92 Urs H lzle Craig Chambers and David Ungar Debugging Optimized Code with Dynamic Deoptimization In Proceedings of the ACM SIGPLAN 92 Conference on Programming Language Design and Implementation San Francisco June 1992 Published as SIGPLAN Notices 27 7 July 1992 Hoe94 Urs Holzle Adaptive Optimization for SELF Reconciling High Performance with Exploratory Program ming Ph D Thesis Stanford University August 1994 HU94 Urs H lzle and David Ungar A Third Generation SELF Implementation Reconciling Responsiveness with Performance In Proceedings of OOPSLA 94 October 1994
167. nt and persistent manner They can be saved in snapshots and filed out and used with any kind of display or printer if printing were supported The details of color map management are handled by each kind of canvas in a way appropriate for the underlying medium For example a canvas for a gray scale display might map colors to shades of gray according to brightness 7 12 2 Specifying Fonts When drawing text in morphic the font s name and size are specified independently The size parameter specifies the font height in pixels and typically ranges from 6 to 72 or more The capital letters of a 72 pixel font are about an inch 106 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 high on a typical display This interface suggests that the underlying graphics system fonts can be scaled arbitrarily and indeed many modern X servers do support scalable fonts The scheme that was implemented for Self 4 0 has not survived the Macintosh port In order to allow portable specification of fonts we have introduced a font Spec prototype that holds a font s family name e g times a font style e g bold and a font size e g 12 This object uses an immutable public protocol it responds to copy Name copyName Style copyName Style Size etc Once you have created a fontSpec object you can then pass it to for example a label morph myLabel fontSpec fontSpec copyName helveti
168. nu to operate on morphs below the surface and can be used to insert or remove morphs from a composite morph Holding the left mouse button over the squares along the left side of the core sampler highlights the associated morph As a shortcut holding down the shift key while pressing the left mouse button over one of these squares will extract the associated submorph and all its submorphs from the composite morph Holding the shift key while dropping a morph onto one of these squares will insert the morph as a submorph of the associated morph The iconic buttons on the right show the current resizing attributes of the associated morph and allow them to be changed Resizing attributes are discussed in section 7 7 3 Morph Traits and Prototypes Morphic organizes morphs into a hierarchy much like a class hierarchy The behavior for all instances of a given morph class is defined in a shared traits object which is a parent of all the instances The structure of an instance is defined by the slots of its prototype The root of the morph hierarchy is traits morph All morphs inherit from traits morph either directly or via one or more intermediate traits objects Note to see the entire morph hierarchy invoke the Show Traits Family menu command on an outliner on traits morph in the user interface Be patient the morph hierarchy is quite large Usually the prototype of a given morph contains all the slots of the morph from which it i
169. nversion 8 13 9 C glue Since C is a superset of C all of C glue can be used with C In addition C glue provides support for 122 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 e Constructing objects using the new operator e Deleting objects using the delete operator e Calling member functions on objects Each of these parts will be explained in the following sections 8 13 10 Constructing objects In C objects are constructed using the new operator Constructors may take arguments The macros CC_new_N where N is a small integer support calling constructors with or without arguments Calling a constructor is similar to calling a function so for additional explanation please refer to section 5 13 6 Here is the general syntax for constructing objects using C glue CC_new_N cnvt_res aux_res class gfname c0 a0 cl al cN aN For example to construct a sockaddr_int object the following glue statement could be used CC_new_0 proxy sockaddr_in socks sockaddr_in new_sockaddr_in The meanings of the CC_new_N arguments are as follows cnvt_res aux_res the result of calling the constructor is an object pointer The result conversion pair cnvt_res aux_res see Table 3 specifies how this pointer is converted to a Self object before being returned In the sockaddr example the proxy result conversion is used e class is the name of the class or struc
170. nymous parent slot that is initialized to point to the activation object for the lexically enclosing block or method As a result implicit receiver messages 2 3 4 sent within a block method are lexically scoped The block method object s anonymous parent slot is invisible at the Self level and cannot be accessed explicitly For example the block 3 4 looks like 3 All block objects have the same parent an object containing the shared behavior for blocks 2 1 Objects 7 Self Handbook Documentation Release 2 for Self 4 4 enclosing method s traits block activation object N mm i A N pn oft block bi The block method s selector is based on the number of arguments If the block takes no arguments the selector is value If it takes one argument the selector is value If it takes two arguments the selector is value With for three the selector is value With With and for more the selector is just extended by enough With s to match the number of block arguments Block evaluation has two phases In the first phase a block object is created because the block is evaluated e g it is used as an argument to a message send The block is cloned and given a pointer to the activation record for its lexically enclosing scope the current activation record In the second phase the block s method is evaluated as a result of sending the block the appropriate variant of the value message The block meth
171. o arg up to the limit returns a vector of mirrors on all objects referring to argument s re flectee up to the limit allows one to find references to a method returns a vector of mirrors on all objects with a parent slot referring to the given object up to the limit returns a vector of mirrors on objects with slots whose names match the given selector up to the limit returns a vector of mirrors on methods whose selectors match the given selector up to the limit Debugging halt halt the current process halt halt and print a message string error halt print an error message and display the stack warning beep print a warning message and continue Virtual Machine Generated Errors undefinedSelector Type Delega tee MethodHolder Arguments ambiguousSelector Type Delega tee MethodHolder Arguments missingParentSelector Type Del egatee MethodHolder Argu ments performTypeErrorSelector Type Delegatee MethodHolder Argu ments mismatchedArgumentCountSelector Type Delegatee MethodHolder Arguments primitiveFailedError Name lookup found no matching slot lookup found more than one matching slot parent slot through which resend was delegated was not found first argument to the _Perform primitive was not a canonical string number of args supplied to _Perform primitive does not match selector the named primitive failed with given error string Other system triggered messa
172. o arguments the first being a proxy representing a sockaddr_in struct the second being a short integer After converting types set_sin_port_glue performs the assignment first_converted_arg sin_port second_converted_arg In general the meaning of the C_get_comp and C_set_comp arguments is cnvt_res aux_res how to convert the value of the component that is being read to a Self object Any of the result conversions found in Table 3 may be applied e cnvt_strc aux_strc the conversion that is applied to produce a struct upon which the operation is per formed In the sin_port example this conversion is a proxy conversion implying that in Self the struct whose sin_port component is assigned is represented by a proxy object In general any of the argument conversions from Table 3 that results in a pointer may be used comp is the name of the component to be read or assigned In the sin_port example this name is sin_port Note that it includes a This e g allows handling pointers to int s by pretending that it is a pointer to a struct and operating on a component with an empty name e gfname the name of the C function that C_get_comp or C_set_ comp expands into e expr_co expr_a0 when assigning to a component the value it is assigned is obtained by converting a Self object to a C value The expr_co expr_a0 pair which can be any one of the argument conversions listed in Table 3 specifies how to do this co
173. o explicit receivers 17 print 5 factorial Associativity Unary messages compose from left to right An expression to print 5 factorial for example is written 5 factorial print and interpreted as 5 factorial print Precedence Unary messages have higher precedence than binary messages and keyword messages 2 3 2 Binary messages A binary message has a receiver and a single argument separated by a binary operator Examples of binary messages 3 4 7 lt gt 8 Associativity Binary messages have no associativity except between identical operators which associate from left to right For example 3 4 7 is interpreted as 3 4 7 But 3 4x 7 is illegal the associativity must be made explicit by writing either SS APR Or 3 4 T7 Precedence The precedence of binary messages is lower than unary messages but higher than keyword messages All binary messages have the same precedence For example 3 factorial pi sine is interpreted as 3 factorial pi sine 2 3 3 Keyword messages A keyword message has a receiver and one or more arguments It is written as a receiver followed by a sequence of one or more keyword argument pairs The first keyword must begin with a lower case letter or underscore _ subsequent keywords must be capitalized An initial underscore denotes that the operation is a primitive A keyword message consists of the longest possible sequence of such keyword argument pairs
174. o get events even when the cursor is no longer over the morph For example a click to type editor should continue to get keyDown events until another editor is clicked In short Morphic supports both spatial and subscription based event dispatching because both are useful The events generated by a particular user are dispatched from the handMorph associated with that user Each hand Morph keeps a list of subscribers interested in various kinds of events A morph asks the appropriate handMorph to start or stop its subscription to a particular kind of event Every event has a reference to the hand that generated that even Thus a morph that wishes to track the mouse until the button is released e g sliderMorph would do the following 1 on leftMouseDown execute evt sourceHand subscribeUntilAllUp self 2 on mouseMove update the slider position from the current mouse position which is in global coordinates 7 5 2 Mapping special characters to actions When a morph receives the keyDown message the next step is the interpretation of any control meta or command keystrokes For example on the Macintosh a command X should perform a cut opera tion A morph wishing to respect these conventions should do two things it should inherit from traits ui2Event ignoreSpecialCharactersMixin and it should upon receiving the keyDown message send sendMessageToHandleKeyboardEventTo the event passing itself as the argument The latter message
175. object Slots in Module On the module menu see below shows all slots in a given module Added or Changed On the module menu see below shows all slots added or changed in the module since it Slots in Module was filed out Removed Slots in On the module menu see below shows the names of the slots removed from the Module mod ule since it was last filed out Expatriate Slots On the changed module menu see below shows all slots in filed out objects that do not themselves specify a module These slots will not be filed out The copy down and module enumerators will be covered later The other enumerators can be summoned from several places the outliner menu the slot menu and the text editor menu As a shortcut selecting a whole expression in the text editor and then asking for an enumera tor will bring up the enumerator to search for the outermost message send in the expression So if you select the following expression aSet findFirst elem IfPresent snort IfAbsent sludge and choose implementors from the text editor menu you will get an Implementors enumerator ready to search for findFirst IfPresent IfAbsent Of course you can always change the search target by double clicking and editing the text The text editors also implement a host of handy double clicking shortcuts Finally there is one last detail about enumerations many contain a check box to choose Wellknown only This is always checked by default to spe
176. od is then cloned the argument slots of the clone are filled in the anonymous parent slot of the clone is initialized using the scope pointer determined in phase one and finally the block s code is executed It is an error to evaluate a block method after the activation record for its lexically enclosing scope has returned Such a block is called a non lifo block because returning from it would violate the last in first out semantics of activation object invocation This restriction is made primarily to allow activation records to be allocated from a stack A future release of Self may relax this restriction at least for blocks that do not access variables in enclosing scopes 2 1 8 Returns A return is denoted by preceding an expression by the operator A return causes the value of the given expression to be returned as the result of evaluating the method or block Only the last expression in an object may be a return The presence or absence of the operator does not effect the behavior of ordinary methods since an ordinary method always returns the value of its final expression anyway In a block however a return causes control to be returned from the ordinary method containing that block immediately terminating that method s activation the block s activation and all activations in between Such a return is called a non local return since it may return through a number of activations The result of the ordinar
177. on a block methodMirror Prototypical mirror on a normal method blockMethodMirror Prototypical mirror on a block method methodActivationMirror Prototypical mirror on a method activation blockMethodActivationMirror Prototypical mirror on a block activation proxyMirror Prototypical mirror on a proxy fctProxyMirror Prototypical mirror on a fctProxy profilerMirror Prototypical mirror on a profiler 8 12 Option Primitives This section has not been updated to include all options present in Self 4 0 Option primitives control various aspects of the Self system and its inner workings Many of them are used to debug or instrument the Self system and are probably of little interest to users The options most useful for users are listed in Table 2 other option primitives can be found in Appendix 5 B and a list of all option primitives and their current settings can be printed with the primitive_PrintOptionPrimitives Table 2 Some useful option primitives Name Description _PrintPeriod Print a period when reading a script file with _RunScript Default false _PrintScriptName Print the file name when reading a script file Default false _Spyl Start the system monitor see Appendix 5 A for details Default false _StackPrintLimit Controls the number of stack frames printed by _PrintProcessStack De fault 20 _DirPath The default directory path for script files Each option primitive controls a variab
178. on is empty return number of elements in collection Adding 75 Self Handbook Documentation Release 2 for Self 4 4 add add argument element to collection receiver addAll add all elements of argument to receiver at Put add key value pair at Put IfAbsent add key value pair evaluating block if key is absent addFirst add element to head of list addLast add element to tail of list copyAddAll return a copy containing the elements of both receiver and argument copyContaining return a copy containing only the elements of the argument Removing remove remove the given element remove IfAbsent remove the given element evaluating block if absent removeAll remove all elements removeFirst remove first element from list removeLast remove last element from list removeAllOccurences remove all occurrences of this element from list removeKey remove element at the given key removeKey IfAbsent remove element at the given key evaluating block if absent copyRemoveAll return an empty copy Accessing first return the first element last return the last element includes test if element is member of the collection occurrencesOf return number of occurences of element in collection findFirst IfPresent IfAbsent evaluate present block on first element found satisfying criteria absent block if no such element at return element at the given key at IfAbsent return element at the given key evaluating block if
179. on resulting from performing a return i e eval uating an expression preceded by the operator from within a lexically enclosed block A non local return forces returns from all activations between the method activation and the activation of the block performing the return e The method holder of a method is the object containing the slot holding that method e The sending method holder of a message is the method holder of the method that sent it e A message is a request to an object to perform some operation The object to which the request is sent is called the receiver A message send is the action of sending a message to a receiver e A primitive send is a message handled by invoking a primitive a predefined function provided by the Self implementation 135 Self Handbook Documentation Release 2 for Self 4 4 Messages that do not have an explicit receiver are known as implicit receiver messages The receiver is bound to self A unary message is a message consisting of a single identifier sent to a receiver A binary message is a message consisting of an operator and a single argument sent to a receiver A keyword message is a message consisting of one or more identifiers with trailing colons each followed by an argument sent to a receiver Unary binary and keyword slots are slots with selectors that match unary binary and keyword messages respectively An argument slot is a slot in a method filled in with
180. on the triangle to expand the object and see more information Now it shows a summary of modules containing the slots in this object Gust programmingExamples here four slots and a category containing more slots although those slots are not shown yet Categories Clicking the top triangle now would collapse this object outliner but instead look inside the category by clicking its triangle And one more click expands the subcategory 1 Double clicking on the triangle will expand or contract all levels instead of just a single level This feature was added in Self 4 1 2 46 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4 anExampleObject Al Ef x Module programming Examples parent traits clonable anUncategorized Constant 3 14159 anUncategorizedMethod userQuery report Hello there B anUncategorzed Variable 17 3i a category of slots 4 anExampleO bject Aj Ej X Module programming Examples parent traits clonable anUncategonzed Constant 3 14159 anUncategonzedMethod userQuery report Hello there El anUncategorzed Variable 17 3 4a category of slots aCategonzed Constant 3 14159 aCategonzedMethod userQuery report Hello there B aCategorzed Variable 17 3i a subcategory 5 2 Browsing Concepts 47 Self Handbook Documentation Release 2 for Self 4 4 4 anExampleO bject Module programmingbamples parent traits clonab
181. onable anUncategonzed Constant 3 14159 anUncategonzed Method user Query report Hello there E anUncategorized Variable 17 y 4 a category of slots aCategorizedConstant 314159 aCategonzedMethod user Query report Hello there El aCategorzed Varable 17 y slotName slotContents Or slotName lt slotContents Examples Constants pi 3 14159 greetUser userQuery report hi A method body x add x Binary select take a single add a To b a b Keyworded not one or more a Assignables items lt list copyRemoveAll Can access th it using it 4a subcalegory whoAml mr os environmentAt LOGNAME IfFail The Phantom whoAmI Geit Doi Close 56 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 4 anExampleO bject Aj E x Module programming bamples parent traits clonable anUncategorizedConstant 3 14159 anUncategonzed Method user Query report Hello there E anUncategorizedVanable 17 3 4a category of slots aCategonzedConstant 3 14159 aCategonzedMethod user Query report Hello there El aCategonzed Variable 17 3 me lt Gumby 4a subcategory who Aml os environmentAt LOGNAME IfFail The Phantom whoAmI Getit Do Close 5 2 Browsing Concepts 57 Self Handbook Documentation Release 2 for Self 4 4 4 anExampleObject Al E X Module programmuingExamples parent
182. or exit quit ifTrue exit exit exit quit ifTrue exit value expr exitValue The first expression evaluates to nil if the block exits early the second allows the programmer to define the expression s value when the block exits early Note These constructs should not be confused with their looping counterparts loopExit and loopExitValue Module block 3 3 4 Other Block Behavior Blocks have some other useful behavior e One can determine the time in milliseconds required to execute a block using various ways of measuring time using the messages userTime systemTime cpuTime and real Time e One can profile the execution of a block using the messages profile and flatProfile profile prints out the source level call graph annotated with call site and timing information whereas flatProfile prints out a flat profile sorted by module e The message count Sends will collect lookup statistics during a block execution Any object that inherits from the lobby can be passed to a method that expects a block behavior in defaultBehavior makes the object behave like a block that evaluates to that object Module block 3 4 Numbers and Time The SELF number traits form the hierarchy shown below In this and subsequent hierarchy descriptions indentation indicates that one traits object is a child of another The prefix traits is omitted since these hierarchy descriptions al
183. or if a block is evaluated whose lexically enclosing scope has already returned Since these errors are nonrecoverable they cannot be caught by the same Self process the scheduler if running is notified 8 4 Low level error messages Five kinds of errors can occur during the execution of a Self program lookup errors primitive errors programmer defined errors non recoverable errors and fatal VM errors All but the last of these are usually caught and handled by mechanisms in the programming environment resulting in a debugger being presented to the user However if programs are run without the programming environment or the error handling mechanisms themselves are broken low level error facilities are used This section describes the various error messages presented by the low level facilities For each category or error the general layout of error messages in that category will be explained along with the format of the stack trace Then a rogue s gallery of the errors in that category will be shown By default errors are handled by a set of methods defined in module errorHandl ing For all errors except nonre coverable and fatal VM errors an object can handle errors in its own way by defining its own error handling methods If the object in which an error occurs neither inherits nor defines error handling behavior the VM prints out a low level error message and a stack trace The system will also resort to this low level message
184. ound no parent slot fish which was explicitly specified as the delegatee of the message 8 7 Programmer defined errors These are explicitly raised in the Self program to report errors e g sending the message first to an empty list will cause such an error Error first is absent Receiver is list lt 7 gt Use the selectors error and error Arguments to raise a programmer defined error 8 8 Primitive errors Primitive failures occur when a primitive cannot perform the requested operation for example because of a missing or invalid argument badTypeError the _IntAdd primitive failed Its receiver was shell lt 6 gt The primitive failed with badTypeError because the shell in not an integer The selector 12 could not be sent to shell because it is not a string The primitive _Perform expects a string as its first argument The selector add could not be sent to shell lt 0 gt because it does not take 2 argumen The primitive _Perform received the wrong number of arguments 8 6 Lookup errors 111 Self Handbook Documentation Release 2 for Self 4 4 There are many other kinds of possible primitive errors 8 9 Nonrecoverable process errors Errors that stop a process from continuing execution are referred to as nonrecoverable errors The stack has grown too big Self 4 0 limits stack sizes and cannot resume processes with stack overflows A stack overflow error occurs because the cur
185. oup Rather than simply presenting a set of rules an attempt has been made to explain the reasons for each stylistic convention While these conventions have proven useful to the Self group they should be taken as guidelines not commandments Self is still a young language and it is likely that its users will continue to discover new and better ways to use it effectively 4 1 Behaviorism versus Reflection One of the central principles of Self is that an object is completely defined by its behavior that is how 1t responds to messages This idea which is sometimes called behaviorism allows one object to be substituted for another without ill effect provided of course that the new object s behavior is similar enough to the old object s behavior For example a program that plots points in a plane should not care whether the points being plotted are represented internally in cartesian or polar coordinates as long as their external behavior is the same Another example arises in program animation One way to animate a sorting algorithm is to replace the collection being sorted with an object that behaves like the original collection but as a side effect updates a picture of itself on the screen each time two elements are swapped behaviorism makes it easier to extend and reuse programs perhaps even in ways that were not anticipated by the program s author It is possible however to write non behavioral programs in Self For example a prog
186. own as submorphs Note that the terms composite and submorph refer to roles that can be played by any morph Submorphs can be added to any kind of morph even morphs such as circleMorphs or labelMorphs that are atomic in some other systems Copying deleting moving drawing and layout operations are applied to the composite morph as a whole The structure of a composite morph forms a tree When morph B is a submorph of morph A B s owner is A and B appears in A s submorphs list A morph can only be a submorph of at most one morph at a time so its owner is a single value not a collection A window containing a collection of morphs is itself just a morph known as a worldMorph Each user s cursor is represented by a handMorph Grabbing a morph with the mouse is implemented by removing the target morph from the worldMorph and adding it to the handMorph Dropping a morph when the mouse is released is implemented by reversing this process A handMorph is itself a submorph of its world The message root can be sent to a morph to get the top most owner of a composite morph stopping just short of the worldMorph or handMorph that contains it If a morph is not a submorph of any morph its owner is nil rowMorph ui2Button ui2Button Off labelMorph circleMorph circleMorph Figure 7 2 Figure 2 A composite morph consisting of a row with two buttons Each button has submorph to indicate its function one is a piece of text the other is
187. phs have been retro fitted with implementations of these messages The enterprising user could easily infer how to add the required support to morphs that do not yet have it Suppose one has created a column of useful buttons that one wishes to save Fortunately buttons columns rows frames and labels are among the morphs that do support saving To save this morph create an outliner for it and then evaluate in that outliner saveMorphInFile The system will prompt for a file name and will give graphical feedback as each component morph is stored The file can later be read by evaluating worldMorph loadMorphFromFile Again the system will prompt for the file name A copy of the morph that was saved will be added to the hand The return value of the expression will also be added to the hand which may temporarily hide the new morph Click any mouse button to put down the two objects then move the top one out of the way 7 5 Handling User Input 7 5 1 Handling Events Morphic represents user actions such as pressing a key or mouse button using ui2Event objects A ui2Event actually carries two kinds of information its type such as leftMouseDown and the state of the mouse buttons and certain keyboard keys when the event occurred This allows a program to tell for example if the shift key was held down when the left mouse button was pressed As events occur they are placed into a buffer Morphic removes and processes events from
188. r the result is a pointer to the indexed byte 8 13 15 Result conversions from C C to Self A result conversion is given a C or C value of a certain type and performs these actions to produce a corresponding Self object e check that the C C value can be converted to a Self object with no overflow or other error occurring If not report the error e do the conversion i e construct the Self object corresponding to the given C C value Table 4 lists all the available result conversions Each row represents one conversion with the first two columns designating the conversion pair The third column lists the type of C or C value that the conversion pair accepts The fourth column lists the type of Self object the conversion produces The fifth column lists the kind of errors that can occur during the conversion Finally the sixth column contains references to numbered notes The notes are found in the paragraphs following the table Table 4 Result conversions from C C to Self 8 13 Interfacing with other languages 127 Self Handbook Documentation Release 2 for Self 4 4 Conversion Second part C C type Self type Errors Notes void void smallInt 0 bool int boolean char char smallInt signed_char signed char smallInt unsigned_char unsigned char smallInt short short smallInt signed_short signed short smallInt unsigned_short unsigned smallInt short int int smallInt overflowError signed_int signed int
189. r of some other object For example the predicate used to order objects in a priorityQueue can be specified using an inline object queue priorityQueue copyRemoveAll queue sorter element el Precedes e2 el gt e2 A block cannot be used here because the current implementation of Self does not support non LIFO blocks and the sorter object may outlive the method that creates it There are undoubtedly other uses of inline objects Inline objects do not generally inherit from the lobby 4 3 Naming and Printing When debugging or exploring in the Self world one often wants to answer the question what is that object The Self environment provides two ways to answer that question First many objects respond to the print String message with a textual description of themselves This string is called the object s printString An object s printString can be quite detailed standard protocol allows the desired amount of detail to be specified by the requestor For example the printString for a collection might include the printStrings of all elements or just the first few Not all objects have printStrings only those that satisfy the criteria discussed in section 4 3 2 below The second way to describe an object is to give its path name A path name is a sequence of unary selectors that describes a path from the lobby to the object For example the full path name of the prototype list is globals list A path name
190. ram that examines and manip ulates the slots of an object directly rather than via messages is not behavioral since it is sensitive to the internal representation of the object Such programs are called reflective because they are reflecting on the objects and using them as data rather than using the objects to represent something else in the world Reflection is used to talk about an object rather that talking to it In Self this is done with objects called mirrors There are times when reflection is unavoidable For example the Self programming environment is reflective since its purpose is to let the programmer examine the structure of objects an inherently reflective activity Whenever possible however reflective techniques should be avoided as a matter of style since a reflective program may fail if the internal structure of its objects changes This places constraints on the situations in which the reflective program can be reused limiting opportunities for reuse and making program evolution more difficult Furthermore reflective programs are not as amenable to automatic analysis tools such as application extractors or type inferencers Programs that depend on object identity are also reflective although this may not be entirely obvious For example a program that tests to see if an object is identical to the object t rue may not behave as expected if the system is later extended to include fuzzy logic objects Thus like reflection it i
191. re So use a facility called Find Slot that takes a pattern and an object and finds any matching slots in that object or its parents Use the middlebutton on the outliner s title macOSGlobals os to get the object menu and select Find slot Slots matching foo 4 Starting lookup from macOSGlobals OS Double click on the word foo to select that field for editing The same trick works on slot names 60 Chapter 5 How to Program in Self Self Handbook Documentation Release 2 for Self 4 4 Slots matching A Starting lookup from macO SGlobals os Since we are searching for a method with Variable in its name backspace the delete key on the Mac three times 7 to erase the foo type in Variable hit the green button and then hit the triangle to start the search if you make a typing mistake you can double click the text to make it editable again The triangle will blink a bit while it is searching one could do other things in the meantime during a long search then the enumerator will show the match es Slots matching Vanable Starting lookup from macOSGlobals os constraint Variable in globals Clicking on the little square button s would show the exact method s But for our purposes just knowing the name is enough and now you have to fix it So back to the debugger and click on the method button on the right in the whoAml slot to expand the stack frame for the whoAmI m
192. reign routine can be invoked by sending the primi tive messages Call _Call With _CallAndConvert With And to the fctProxy representing it Note that fct Proxy objects are low level Most if not all uses of foreign routines should use the interface provided by foreignFct objects Proxies and fct Proxies can be freely cloned However a cloned proxy will be dead A dead proxy is revived when it is used by a foreign function to e g return a pointer The return value of the foreign function together with a type seal is stored into the dead proxy which is then revived and returned as the result of the foreign routine call The motivation for this somewhat complicated approach is that there will be several different kinds of proxies in a typical Self system Different kinds of proxies may have different slots added so rather than having the foreign routine figure out which kind of proxy to clone for the result the Self code calling the foreign routine must construct and pass down an empty dead proxy to hold the result This proxy is called a result proxy and it is the last argument supplied to the foreign function 8 13 2 Glue code Glue code is responsible for the transition from Self to foreign routines It forms wrappers around foreign routines There is one wrapper per foreign routine A wrapper takes a number of arguments of type oop and returns an oop oop is the C type for reference to Self object When a wrapper is exe
193. rent version of Self allocates a fixed size stack for each process and the stack cannot be expanded Self 4 0 cannot run a block after its enclosing method has returned Self cannot resume this process either This error occurs if a block is executed after its lexically enclosing method has returned This is called a non LIFO block Non LIFO blocks are not supported by the current version of Self 8 10 Fatal errors In rare cases the virtual machine may encounter a fatal error e g a resource limit is exceeded or an internal error is discovered When this happens a short menu is displayed VM Version 4 0 5 Tue 27 Jun 95 13 35 49 Solaris 2 x svr4 Internal error signal 11 code 3 addr 4 pc Oxlac768 Do you want to 1 Quit Self optionally attempting to write a snapshot 2 Try to print the Self stack 3 Try to return to the Self prompt 4 Force a core dump Your choice The first two lines help the Self implementors locate the problem Printing the Self stack may provide more information about the problem but does not always work Returning to the Self prompt may be successful but the system integrity may have been compromised as a result of the error The safest course is to attempt to write a snapshot if there are unsaved changes and then check the integrity of the snapshot by executing the primitive _Verify after starting it If there are any error messages from the primitive do not attempt to continue using t
194. rgument predecessor predecessor successor successor raise receiver to integer power logarithm of argument base receiver rounded down to integer square square root factorial fibonacci signum 1 0 1 true if receiver is even true if receiver is odd amp E amp II AM complement lt lt gt gt lt gt and or xor bitwise complement logical left shift logical right shift arithmetic left shift arithmetic right shift Logical operations booleans 28 and Il or AN xor not logical complement Constructing point construction receiver and argument are integers rectangle construction receiver and argument are points HH rectangle construction receiver is a point argument is an extent amp collection construction result can be converted into collection concatenation Printing 74 Chapter 6 Useful Selectors Self Handbook Documentation Release 2 for Self 4 4 print printLine printString printStringDepth printStringSize printStringSize Depth print object on stdout print object on stdout with trailing newline return a string label return a string label with depth limitation request return a string label with number of characters limitation request return a string label with depth and size limitation request Control Block evaluation value With evaluate a block passing arguments Selection ifTrue evaluate argument
195. rong type badTypeSealError Proxy s type seal did not match expected type seal divisionByZeroError Division by zero overflowError Integer overflow This can occur in integer arithmetic primitives or in UNIX when the result is too large to be represented as an integer badSignError Integer receiver or argument has wrong sign alignmentError Bad word alignment in memory badIndexError The vector index e g in _At is out of bounds too large or negative badSizeError An invalid size of a vector was specified e g attempting to clone a vector with a negative size see _Clone Filler and _CloneBytes Filler below reflectTypeError A mirror primitive was applied to the wrong kind of slot e g _Mirror ParentGroupAt to a slot that isn t a parent slot outOfMemoryError A primitive could not complete because its results would not fit in the existing space stackOverflowError The stack overflowed during execution of the primitive or program slotNameError Illegal slot name argumentCountError Wrong number of arguments unassignableSlotError This slot is not assignable lonely AssignmentSlotError Assignment slot must have a corresponding data slot parallel TWAINSError Can not invoke TWAINS primitive another process is already using it noProcessError This process does not exist noActivationError This method activation does not exist noReceiverError This activation has no receiver noParentSlot This activation has no lexical p
196. ry middle menu then type in the new slot name or lt and contents of slot or just name alone for vari able slot containing nil then hit green button to accept Move in slot middle menu then drag to another object Adding Moving Removing a slot Adding adding a new Moving a slot Copying a slot Copy in slot or category middle Copying a slot menu then drag the slot to another object Changing a slot Edit a slot Edit on a slot middle button To change the contents of a constant Edit slot name or its argument names Change a method in a slot Change the visibility of a slot menu then make any changes in the text editor then hit green button to accept changes Double click on the name of the slot wait for red and green buttons to appear on the right of the name edit the name then hit the green button Click on the method icon button on the right of the slot to open a text editor on the method Make the changes then click on the green button to accept them On the slot s middle menu choose Make Public Make Private or Make Undeclared data slot or to change contents and set initial value at same time or to change a slot from data to method or from constant to variable To change a slot s name or the names of its arguments To fix a bug in a method The Self interface uses bold nor mal and sans serif fonts to indi cate public pr
197. s are methods that are not embedded in other code A method can have argument slots 2 2 3 and or local slots An ordinary method always has an implicit parent 2 2 4 argument slot named self Ordinary methods are Self s equivalent of Smalltalk s methods If a slot contains a method the following steps are performed when the slot is evaluated as the result of a message send e The method object is cloned creating a new method activation object containing slots for the method s argu ments and locals e The clone s self parent slot is initialized to the receiver of the message e The clone s argument slots if any are initialized to the values of the corresponding actual arguments e The code of the method is executed in the context of this new activation object For example consider the method arg arg arg This method has an argument slot arg and returns the square of its argument 2 1 7 Blocks Blocks are Self closures they are used to implement user defined control structures A block literal delimited by square brackets defines two objects the block method object containing the block s code and an enclosing block data object The block data object contains a parent pointer pointing to the object containing the shared behavior for block objects and a slot containing the block method object Unlike an ordinary method object the block method object does not contain a self slot Instead it has an ano
198. s _AsObjectlfFail and _ IntAdd becomes _IntAdd IfFail gt x3 _IntAdd a IfFail terror name name failed with error printLine 0 x _IntAdd failed with badTypeError 0 The primitive returns the result of evaluating the failure block When a primitive fails if the primitive call has an IfFail part the message value With issentto the IfFail argument passing two strings the name of the primitive and an error string indicating the reason for failure If the failing primitive call does not have an IfFail part the message primitive FailedWith is sent to the receiver of the primitive call with the same two strings as arguments The result returned by the error handler becomes the result of the primitive operation 0 in our example execution then continues normally If you want the program to be aborted you have to do this explicitly within the error handler for example by calling the standard error method defined in the default world The following table lists the error string prefixes passed by the VM to indicate the reason of the primitive failure If the error string consists of more than the prefix it will reveal more details about the error Table 8 Primitive failures Prefix Description primitiveNotDefinedError Primitive not defined primitiveFailedError General primitive failure for example an argument has an invalid value badTypeError The receiver or an argument has the w
199. s best to avoid using object identity One exception to this guideline is worth mentioning When testing to see 1f two collections are equal observing that the collections are actually the same object can save a tedious element by element comparison This trick is used in several places in the Self world Note however that object identity is used only as a hint the correct result will still be computed albeit more slowly if the collections are equal but not identical Sometimes the implementation of a program requires reflection Suppose one wanted to write a program to count the number of unique objects in an arbitrary collection The collection could in general contain objects of different 39 Self Handbook Documentation Release 2 for Self 4 4 possibly incomparable types In Smalltalk one would use an IdentitySet to ensure that each object was counted exactly once IdentitySets are reflective since they use identity comparisons In Self the preferred way to solve this problem is to make the reflection explicit by using mirrors Rather than adding objects to an IdentitySet mirrors on the objects would be added to an ordinary set This substitution works because two mirrors are equal if and only if their reflectees are identical In short to maximize the opportunities for code reuse the programmer should e avoid reflection when possible e avoid depending on object identity except as a hint and use mirrors to make reflect
200. s between the sub morphs of a composite morph Its argument is a dictionary mapping submorphs in the old composite 102 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 original copy frameMorph frameMorph a display IN display row button button2 button button2 b frameMorph frameMorph display row display row button button2 button button2 Figure 7 16 Figure 16 Copying a composite morph First the submorph structure of the original morph is copied a Then references among the submorphs of the composite updated to mirror those of the original b 7 10 Morph Responsibilities 103 Self Handbook Documentation Release 2 for Self 4 4 morph to the corresponding submorphs in the copy Morphs whose slots may contain references to other morphs within a composite should override this message to update these slots during copying For exam ple a ui2ButtonMorph overrides this message in order to update its target slot That way if the button and its target are both embedded in some composite morph that is copied the button in the copy will refer to the target in the copy See traits colorChangerMorph for an example 7 11 Some Useful Morphs The Self system comes with a large library of morphs While some morphs exist solely to supporting the programming environment many are general purpose and can be reused to construct new applications This section ment
201. s derived the instance vari able of its superclass in a class based system plus possibly a few additions To simplify the life of the programmer the programming environment supports an idiom known as copying down The derived prototype is described differ entially That is it is just like its copy down parent except with particular slots added deleted or changed Typical class based languages also describe the structure of subclasses differentially a subclass may extend its superclass with additional instance variables However the copy down idiom also allows the derived prototype to selectively omit slots of its copy down parent or change their contents For example the circleMorph prototype is derived from 7 3 Morph Traits and Prototypes 83 Self Handbook Documentation Release 2 for Self 4 4 the morph prototype but it replaces the rawBox slot of the morph prototype with the slots radius and center This would not be possible in most class based languages Note that the class like organization of the morph hierarchy with its parallel traits and prototype hierarchies and its use of the copy down mechanism to propagate slot information down the prototype hierarchy is only one way that Self programs can be organized Other parts of the system such as the world wide web browser are organized differently 7 3 1 Implementing a New Kind of Morph It is easy to make a new kind of morph One typ
202. s returned as the result Note this means that the value of an assignment statement is the left hand side of the assignment statement not the right hand side as it is in Smalltalk C and many other languages This is a potential source of confusion for new Self programmers 2 1 4 Objects with code The feature that distinguishes a method object from a data object is that it has code whereas a data object does not Evaluating a method object does not simply return the object itself as with simple data objects rather its code is executed and the resulting value is returned 2 1 5 Code Code is a sequence of expressions 2 3 These expressions are evaluated in order and the resulting values are discarded except for that of the final expression whose value determines the result of evaluating the code The actual arguments in a message send are evaluated from left to right before the message is sent For instance in the expression But in that case make sure you put a space after the period otherwise you will get an obscure error message from the parser 6 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 l to 5 i By 2 Xx J Do k k print 1 is evaluated first then 5 i then 2 j and then I k k print Finally the to By Do message is sent The associativity and precedence of messages is discussed in section 4 2 1 6 Methods Ordinary methods or simply method
203. sents one conversion with the first two columns designating the conversion pair The third column lists the types of Self objects that the conversion pair accepts The fourth column lists the C types that it produces The fifth column lists the kind of errors that can occur during the conversion Finally the sixth column contains references to numbered notes The notes are found in the paragraphs following the table Calling member functions is similar to calling plain functions so please also refer to section 5 13 6 The difference 1s that an additional object must be specified the object upon which the member function is invoked the receiver in Self terms Calling a member function is accomplished using one of the macros CC_mber_N cnvt_res aux_res cnvt_rec aux_rec mname gfname fail_opt c0 a0 cl al cN aN For example here is how to call the member function zock on a sockaddr_in object given by a proxy T CC_mber_0 bool proxy sockaddr_in socks zock zock_glue The arguments to CC_mber_N are cnvt_res aux_res this pair which can be any of the result conversions from Table 3 specifies how to convert the result of the member function before returning it to Self For example the zock member function returns a boolean cnvt_rec aux_rec the object on which the member function is invoked Often this will be a proxy conversion as in the zock example e mname is the name of the member function In general it
204. sheet can be used to change these attributes 7 8 Animation Animation can be used to make an interactive application seem more alive and can convey valuable information However animation can become annoying if the user has to wait until the animation completes before doing anything else In Morphic animation and user actions are concurrent and multiple animations can be active while multiple users interact with the system an atom 294 type atom parent wagt crcie tor ph center a porra ODO radius il IR morphTypeName om velocity a porte 300i 005 0 Figure 7 15 Figure 15 Three simultaneously active morphs an ideal gas simulation a digital clock and an outliner on the Self object underlying one of the atoms in the simulation The clock updates every second the simulation runs continuously and the outliner periodically updates its center and velocity slot values as the underlying atom moves A morph continues to operate while it is being moved the clock is being moved here or while an external animation is applied to it Note that multiple users can be active simultaneously this example shows the cursors of two users There are two ways to achieve animation First a morph can have lightweight autonomous behavior which typically although not necessarily appears as animation For example a clock might advance the time or a discrete simulation might compute simulation steps Second Morphic includes a kit of external
205. ssage gt receiver binary send resend binary send binary send operator expression keyword message receiver keyword send resend keyword send keyword send small keyword expression cap keyword expression receiver expression resend resend identifier The table below summarizes Self s message syntax rules MES ARGU PRECE ASSOCIATIV SYNTAX SAGE MENTS DENCE ITY Unary 0 highest none receiver identifier binary 1 medium none or receiver operator expression left to right keyword 1 lowest right to left receiver small keyword expression cap keyword expression Heterogeneous binary messages have no associativity homogeneous binary messages associate left to right Parentheses can be used to explicitly specify order of evaluation 7 The current programming environment expects a slot annotation to start with one of a number of keywords including Category Comment and Modulelnfo See the programming environment manual for more details 8 In order to simplify the presentation this grammar is ambiguous precedence and associativity rules are used to resolve the ambiguities 2 3 Expressions 13 Self Handbook Documentation Release 2 for Self 4 4 2 3 1 Unary messages A unary message does not specify any arguments It is written as an identifier following the receiver Examples of unary messages sent t
206. t that is being instantiated e gfname the name of the C function that the CC_new_N macro expands into e ci ai if the constructor takes arguments these arguments must be converted from Self representation to C representation The arguments conversion pairs ci ai specify how each argument is converted See Table 3 for a description of all argument conversions In the sockaddr example there are no arguments 8 13 11 Deleting objects C objects can have destructors that are executed when the objects are deleted To ensure that the destructor is called properly the delete operator must know the type of the object being deleted This is ensured by using the CC_delete macro which has the following form CC_delete cnvt_obj aux_obj gfname For example to delete sockaddr_in objects constructed as in the previous section the CC_delete macro should be used in this manner CC_delete proxy sockaddr_in socks delete_sockaddr_in In general the meaning of the arguments given to CC_delete is e cnvt_obj aux_obj this pair can be any of the argument conversions found in Table 3 that produces a pointer to the object that will be deleted e gfname the name of the C function that this invocation of CC_delete expands into 8 13 Interfacing with other languages 123 Self Handbook Documentation Release 2 for Self 4 4 8 13 12 Calling member functions Table 3 lists all the available argument conversions Each row repre
207. t accesses or method invocations An identifier followed by a left arrow the characters lt and concatenated to form lt and an expression represents an initialized read write variable assignable data slot The object will contain both a data slot of that name and a 2 2 Slot descriptors 9 Self Handbook Documentation Release 2 for Self 4 4 point traits corresponding assignment slot whose name is obtained by appending a colon to the data slot name The initializing expression is evaluated in the root context and the result stored into the data slot at parse time For example an initialized mutable point might be defined as l parent traits point x lt 3 4 Y E producing an object with two data slots xand y and two assignment slots x and y containing the assignment primitive depicted with An identifier by itself specifies an assignable data slot initialized to nil Thus the slot declaration x is a shorthand notation for x lt nil For example a simple mutable point might be defined as x y I producing 2 2 3 Slots containing methods If the initializing expression is an object literal with code that object is stored into the slot without evaluating the code This allows a slot to be initialized to a method by storing the method itself rather than its result in the slot Methods may only be stored in read only slots A method automatically receives
208. t are represented as outliners which can expand to show increasing levels of detail One of these objects has been designed to provide a convenient context for typed in commands and so it is called the shell If the shell is not already present on your screen you can summon it by pressing the middle mouse button on the background and selecting she11 gt shell 4 E x In Self 4 1 outliners now sport three small buttons in the top right hand corner labeled A E and X These buttons summon the object s parents add an evaluator text region to the bottom of the outliner and dismiss the 45 Self Handbook Documentation Release 2 for Self 4 4 outliner Press the E button to get an evaluator Type anExample0bject into the evaluator it will already be selected and hit the Get it button or type metareturn on UNIX or command return on MacOS X gt shell Aj E x anExampleObject Get Do it Close The result object appears in your hand raised above the screen as if you were dragging it with the left button Just click the button to set it down banExampleObject As with most other things on the Self screen the left button picks it up and moves it For buttons and other things that use left button for other purposes you can grab them with marquee selection really the carpet morph in Self or with the Grab item on the right button menu Expand and Collapse Left click
209. t as a dictionary key the object must understand the messages hash and the latter applying to any pair of items in the collection This is because sets and dictionaries are implemented as hash tables Derived from set and dictionary are sharedSet and sharedDictionary These provide locking to maintain internal consistency in the presence of concurrency Modules setAndDictionary sharedSetAndDictionary 3 5 4 Tree Based Sets and Dictionaries collection tree treeNodes abstract treeNodes bag treeNodes set emptyTrees abstract emptyTrees bag emptyTrees set treeSet and treeBag implement sorted collections using binary trees The set variant ignores duplicates while the bag variant does not Tree sets and bags allow both explicit and implicit keys that is adding elements can be done with either at Put or add where a tree set that uses explicit keys behaves like a dictionary Sorting is done on explicit keys if present values otherwise and the objects sorted must be mutually comparable Comparisons between keys are made using compare IfLess Equal Greater The implementation of trees uses dynamic inheritance to distinguish the differing behavior of empty and non empty subtrees The prototype treeSet represents an empty sub tree when an element is added to it its parent is switched from traits emptyTrees set which holds behavior for empty sub trees to a new copy of treeSetNode which represents a tree node holding an el
210. t be passed a dead proxy to revive and store the result in see section 5 13 1 There are only three uses of foreignFct objects in the server and in all three cases the foreignFct object is encapsulated in a method as illustrated above In general the design of foreignFct objects has been aimed at making the use of them light weight When cloning them it is only necessary to specify the minimal information the name of the foreign function They can be encap sulated in a method thus localizing the impact of redesigns The complications of dynamic loading and linking are handled automatically as is the recovery of dead fct Proxies 8 13 Interfacing with other languages 131 Self Handbook Documentation Release 2 for Self 4 4 132 Chapter 8 Virtual Machine Reference CHAPTER NINE REFERENCES APS93 Ole Agesen Jens Palsberg and Michael I Schwartzbach Type Inference of SELF In ECOOP 93 Confer ence Proceedings Kaiserslautern Germany July 1993 Published as Springer Verlag LNCS 707 1993 Age94a Ole Agesen Mango A Parser Generator for SELF Sun Microsystems Labs TR SMLI TR 94 27 1994 Age94b Ole Agesen Constraint Based Type Inference and Parametric Polymorphism In Proc International Static Analysis Symposium Sep 28 30 1994 CU89 Craig Chambers and David Ungar Customization Optimizing Compiler Technology for SELF a Dynamically Typed Object Oriented Programming Language In Proceedings of the SIGPLAN
211. t is a slot holding a data object An assignment slot is a slot containing the assignment primitive An assignable data slot is a data slot for which there is a corresponding assignment slot whose name consists of the data slot s name followed by a colon When an assignment slot is evaluated its argument is stored in the corresponding data slot e An ordinary method or simply method is an object with code and is stored as the contents of a slot The method s name also called its selector is the name of the slot in which it is stored e A block is an object representing a lexically scoped closure similar to a Smalltalk block e A block method is the method that is executed when a block is evaluated by sending it value value value With etc A block method is a special kind of method that is evaluated within the scope of its method and any lexically enclosing blocks e An activation object records the state of an executing method or block method It is a clone of the method prototype used to store the method s arguments and local slots during execution There are two kinds of activation objects ordinary method activation objects or simply method activation objects and block method activation objects e Anon lifo block isa block that is evaluated after the activation of its lexically enclosing block or method has returned This results in an error in the current implementation e A non local return is a return from a method activati
212. tells the event to decode any special characters and send an apprpropriate message back to 1ts argument The mixin provides default behavior 96 Chapter 7 Morphic The Self User Interface Framework Self Handbook Documentation Release 2 for Self 4 4 7 6 Drag and Drop A morph can perform some action when another morph is dropped onto it and can decide which dropped morphs it will accept In addition the dropped morph can perform some action in response to being dropped To accept dropped morphs a morph must respond affirmatively to the message wantsMorph m Event evt The morph to be dropped is supplied as an argument to allow the receiving morph to decide if it wishes to accept the drop For example a printer icon morph might accept only document morphs If the target morph agrees to accept the dropped morph the target is then sent the message addDroppingMorph m Event evt to actually perform the drop action Part of this action should be to put the dropping morph somewhere or delete it For example the printer icon morph might queue a print request then add the document morph to a folder morph representing the printed documents Finally the dropped morph is informed of the drop post facto by sending it the message justDroppedInto m Event evt The event is provided in these messages to allow the morph to examine the state of the mouse buttons or modifier keys at the time of the drop 7 7 Automa
213. the traits object This information is captured by a Creator annotation on each object that gives the path from the Lobby to the slot intended to create the object In this case the transporter just files out a reference to the object s creator cleverly enough so that the actual creator slot does not need to have been already filed in On the other hand if an object is immutable its identity is not important If an object is annotated as is Complete the transporter sends it isImmutableForFilingOut and if that message returns true the transporter never files out a reference For example integers would answer t rue to this message e If the contents of the slot is a simple usually immutable object like 17 3 4 or foo the string the trans porter should just ask the object for a string to store It does this by checking to see if the object is annotated as isComplete to see if it is safe to send the object messages checks to see if this object is itself needed for the string it would be a mistake to file out the prototypical point as 0 0 because the x slot would never be defined then asks the object for a store string To see if the object must itself be filed out it sends storeStringNeeds and if this message does not return the object itself it sends storeStringIfFail If this succeeds the trans porter can save a data type specific string for the object This fairly elaborate mechanism allows programmers to add new kinds of objects t
214. the receiver possibly with embedded copies or initialization Comparing Equality equal l not equal hash hash value s identical the same object this is reflective and should be avoided l not identical Ordered lt less than gt greater than lt less than or equal gt greater than or equal compare IfLess Equal Greater compare IfLess Equal Greater Incomparable three way comparison three way comparison with failure Numeric operations 1 absolute Value inverse negate ceil floor truncate add subtract multiply divide divide exactly returns float divide and round to integer tends to round up divide and round up to integer divide and round down to integer modulus absolute value multiplicative inverse additive inverse round towards positive infinity round towards negative infinity truncate towards zero Continued on next page 73 Self Handbook Documentation Release 2 for Self 4 4 Table 6 1 continued from previous page round asFloat asInteger double quadruple half quarter min max mean pred predecessor succ successor power log square squareRoot factorial fibonacci sign even odd Bitwise operations integers round coerce to float coerce to integer multiply by two multiply by four divide by two divide by four minimum of receiver and argument maximum of receiver and argument mean of receiver and a
215. the system with customized control structures In fact all control stuctures in Self except message sends returns and VM error handling are implemented using blocks 3 3 Blocks Booleans and Control Structures 25 Self Handbook Documentation Release 2 for Self 4 4 3 3 1 Booleans and Conditionals The fundamental control structure is the conditional In Self the behavior of conditionals is defined by two unique boolean objects true and false Boolean objects respond to the messages ifTrue ifFalse ifTrue False and ifFalse True by evaluating the appropriate argument block For example true im plements ifTrue False as ifTrue bl False b2 bl value That is when true is sent ifTrue False it evaluates the first block and ignores the second For example the following expression evaluates to the absolute value of x x lt 0 ifTrue x negate False x The booleans also define behavior for the logical operations AND amp amp OR EXCLUSIVE OR and NOT not Because the binary boolean operators all send value to their argument when necessary they can also be used for short circuit evaluation by supplying a block e g 0 lt i amp amp i lt maxByte pred ifTrue Module boolean 3 3 2 Loops The various idioms for constructing loops in Self are best illustrated by example Here is an endless loop L loop Here are two loops that test for their termi
216. this buffer in order Thus even if a user occasionally gets ahead of the system the system will eventually catch up A morph can handle a given kind of event simply by implementing one of the following messages keyDown evt keyUp evt mouseMove evt leftMouseDown evt leftDoubleClick evt leftMouseUp evt middleMouseDown evt 7 4 Saving a Composite Morph 95 Self Handbook Documentation Release 2 for Self 4 4 middleDoubleClick evt middleMouseUp evt rightMouseDown evt rightDoubleClick evt rightMouseUp evt The event is always supplied so that its state can be examined The default behavior of the leftMouseDown message is to pick up the composite morph containing the morph that gets the event That is the left mouse button generally means move The default behavior of the rightMouseDown message is to pop up the morph menu the blue menu The default behavior of the other messages is to return the special dropThroughMarker object indicating that the event is not processed by this morph Submorphs of a morph are displayed in front of their owning morph By default submorphs are usually given the first opportunity to handle incoming events If a submorph does not handle an event it returns the dropThroughMarker object and Morphic gives the submorph behind it a chance to handle the event Each user generates events at the current location of their cursor One can visualize an event as falling down thro
217. tic Layout 7 7 1 Packing Automatic layout relieves the programmer from much of the burden of laying out the components of a composite morph such as a dialog box By allowing morphic to handle the details of placing and resizing the components the programmer can focus on the topology of the layout without worrying about the exact positions and sizes Automatic layout also allows composite morphs to adapt gracefully to size changes including font size changes Layout morphs manage the placement and sizing of their submorphs Layout morphs currently include rowMorphs columnMorphs frameMorphs and their descendents All other morphs leave the size and placement of their submorphs alone The current set of layout morphs all use the same layout strategy linear non overlapping packing Rows pack horizontally from left to right Columns frames and their descendents pack vertically from top to bottom This simple approach while it does not handle every conceivable layout problem e g tables whose rows and columns adjust to the size of their contents is surprisingly powerful All automatic layout in morphic is based on nested combinations of rows and columns Linear packing is best explained procedurally Consider a rowMorph Its task is to arrange its submorphs into a row such that the left edge of each morph just touches the right edge of the next morph The submorphs are processed in order that is the first submorph will be placed at the left en
218. tory A history of commands typed at the prompt and their results memory memory system interface GC snapshot low space etc monitor system monitor spy control nil indicates an uninitialized value platforms possible hardware platforms preferences user configuration preferences profiling flatProfiling controls Self code profiling prompt interactive read eval print loop scheduler Self process scheduler snapshotAction actions to do before after a snapshot thisHost describes the current host platform times reports user system cpu or real time typeSizes bit byte sizes for primitive types vmProfiling virtual machine profiling 3 13 Should How to build the world you need to reconstruct a world from the source files here s how to do it how to create a default object world by reading in the Self source code provided with your distribution in Optional SelfSource tar Z You can also do this after writing the world out using the transporter transporter fileOut file0utAll To create the default object world 1 Start the Self VM Self Self Virtual Machine Version 4 0 2 Thu 09 Feb 95 19 41 30 Copyright 1989 95 The Self Group type _Credits for credits VM This section describes 2 Optional but recommended Start the spy so you can watch the world fill up with objects VM _Spy true Note that because the world is empty you must use the primitive to do this 3 Read in the default
219. ts and the screen boundaries of other users to be seen The radarView is updated open enough to see where activity is occurring 81 Self Handbook Documentation Release 2 for Self 4 4 The central abstraction of morphic is the graphical object or morph from the Greek for shape or form A morph has a visual representation that can be picked up and moved In addition a morph may 1 perform actions in response to user inputs 2 perform an action when a morph is dropped onto it or when it is dropped onto another morph 3 perform an action at regular intervals and 4 control the placement and size of its submorphs Any morph can have component morphs called submorphs A morph with submorphs is called a composite morph A composite morph is treated as a unit moving copying or deleting a composite morph causes all its submorphs to be moved copied or deleted as well By convention all morphs are visible morphic does not use invisible structural morphs for aggregation This means that if a composite morph is disassembled all its component morphs can be seen and manipulated The remainder of this document discusses the graphics interface that morphs use to draw themselves the structure of composite morphs how to create new kinds of morphs and how to change a morph s behavior with respect to user inputs drag and drop and animation 7 2 Composite Morphs A composite morph is a morph that contains other morphs kn
220. tton to accept the anno tation change Setting creator path tells transporter which slot owns this object and tells environment what to name the object See above Simulates subclassing by allowing an object to contain copies of the slots in another object When copy down parent has slots added changed removed the change prop agates to the copied down children After building a new prototype set isComplete to get the environment to show its printString and to get the transporter to use its storeString Set the module memmbership of a slot the slots in a category or the slots in an object Type in or examine the module for a single slot Change slot initial contents Annotate a slot Select Set Module from the mid dle menu of a slot category or ob ject then for object or category indicate which slots you want to change by choosing which module they currently belong to finally se lect a new module to put the slots in Show Annotation on the slot mid dle menu to expose the annotation then click on the module editor type in the module name then click the green accept button Show Annotation on the slot mid dle menu to expose the annotation then click on the Follow Slot but ton or type the desired initial value expression into the Initial Con tents editor then hit the green ac cept button To ensure that slots are filled out in the correct source fil
221. turns a string which is the result of the encryption To use this function from Self we write a line of C glue Here is the entire file encrypt c containing both the encryption function and the glue 118 Chapter 8 Virtual Machine Reference Self Handbook Documentation Release 2 for Self 4 4 x Make glue available by including it x include incls _glueDefs c incl Naive encryption function x char xencrypt char str int key static char res 1000 TNC Ls for i 0 str i i res i str i key res i M0 return res x Make glue expand to full functions not just prototypes x define WHAT _GLUE FUNCTIONS C_func_2 undef WHAT_GLUE A few words of explanation the last three lines of this file contain the glue code First defining WHAT_GLU1 string encrypt encrypt_glue string int Gl to be FUNCTIONS makes the following line expand into a full wrapper function defining WHAT_GLUE to be PROTOTYPES instead will cause the C_func_2 line to produce a function prototype only The line containing the macro C_func_2 is the actual wrapper for encrypt The 2 designates that encrypt takes 2 arguments The meaning of the arguments from left to right are e string specifies that encrypt returns a string argument e encrypt name of function we are constructing wrapper for e encrypt_glue name that we want the wrapper function to have
222. ual Machine The choice between dynamic and static linking involves a trade off between safety and flexibility as outlined in the following Dynamic linking Dynamic linking has the advantage that it is done on demand so only foreign routines that are actually used in a particular session will be loaded and take up space Debugging foreign routines is also easier especially if the dynamic linker supports unlinking The main disadvantages with dynamic linking is that more things can go wrong at run time For example if an object file containing a foreign routine can not be found a run time error occurs The Sun OS dynamic linker 1d so only handles dynamic libraries which explains why the second stage of glue translation is necessary Static linking Static linking the alternative that was not chosen for Self has the advantage that it needs to be done only once The statically linked in files will then be available for ever after The main disadvantages are that the linked in files will always take up space whether used or not in a given Self session that the VM must be completely relinked every time new code is added and that debugging is harder because there is no way to unlink code with bugs in For these reasons the following examples all use dynamic linking 8 13 4 A simple glue example calling a C function Suppose we have a C function that encrypts text strings in some fancy way It takes two arguments a string to encrypt and a key and re
223. ufficient network bandwidth to support the X traffic Preliminary tests suggest that 30 50 KBytes sec is required between the host machine and each remote user The system has been tested with up to five users active simultaneously A given user can have several Morphic windows open either on the same world or on different worlds and can drag objects among these windows assuming they all belong to the same Self Unix process Core Sampler P Embed in Morph Below gt shell Grab 4a radarView type radarView 7 Modules radar View morphs g gt a frameMorph type frameMorph Duplicate z a m ed Outiinez for Morph spans eae hat haa droits rodorVicw Change Color b Basi Mor ph State Resize Frame Mor ph Siate wass dRadar View siste Evaluate Domim a Row Mor ph Stave oe e E bing a rectangle 178 389 450 347 AS mis E Module rectangle Beep xXx parent wats rectangle corner a por 4S0 547 a Beep origin 3 pow 780389 z NA point 450 347 storeStringNeeds rectngie O 0 1 1 Module point _ parent rais pix x 450 A y 47 3 off zoom out zoomin home lt vi Y Figure 7 1 Figure 1 Three users working in the same space Two of the other users are collaborating so they have made their windows overlap right The third user is working independently in a separate area left The radarView in the third user s area shows the surrounding vicinity in miniature allowing offscreen objec
224. ugh the submorphs of the composite morph at that location until either the event lands on a submorph that handles it or until all the submorphs of the composite at that point are exhausted However events do not fall between top level morphs For example if an outliner is covered by a morph that does not handle middleMouseDown events one cannot invoke the middle button menu of the outliner through the intervening morph In some cases a morph may wish to handle certain events before its submorphs For example a ui2Menu morph handles leftMouseDown events itself rather than letting its component buttons get them in order to highlight the button under the cursor and to pop down the menu when a selection is made A morph can arrange to handle certain kinds of events before its submorphs by overriding the allowSubmorphsToGetEvent message There are actually two classes of events KeyDown events the three mouseDown events and the three doubleClick events are dispatched using the falling through the submorphs technique just described The other events keyUp mouseMove and the three mouseUp events are dispatched only to interested subscribers The rationale is that some morphs are interested in discrete events such as mouseDown transitions while others need to track the mouse or keyboard over an extended period of time Dispatching high frequency events such as mouseMove to uninterested morphs would be inefficient Futhermore some morphs need t
225. uilt at Stanford University by Craig Chambers Urs H lzle Ole Agesen Elgin Lee Bay Wei Chang and David Ungar The project continued at Sun MIcrosystems Laboratories where it benefited from the efforts of Randall B Smith Mario Wolczko John Maloney and Lars Bak Smith and Ungar jointly led it there Work on the project officially ceased in 1995 Release 4 0 contained an entirely new user interface and programming environment designed for serious program ming enabling the programmer to create and modify objects entirely within the environment and then save the object into files for distribution purposes The metaphor used to present an object to the user is that of an outliner allowing the user to view varying levels of detail Also included in the environment is a graphical debugger and tools for navigation through the system Self is available for Solaris Linux and natively on MacOS X under a BSD like licence we would be very interested in anyone prepared to make a Windows port 1 1 System Overview This section contains an overview of the system and its implementation it can be skipped if you wish to get started as quickly as possible Although Self runs as a single UNIX process or a single Macintosh application it really has two parts the virtual machine VM and the Self world the collection of Self objects that are the Self prototypes and programs SELF world SELF virtual machine Figure 1 1 Figure 1
226. ure 5 shows a two stage pipe line Here stdout of the first process is connected to stdin of the second process Figure 8 3 Figure 5 A single UNIX process and an pipe line Figure 5 illustrates a simple trick that in many situations allows Self processes to behave as if they are full fledged UNIX processes A Self process is represented by a real UNIX process which transparently communicates with the Self process over a pair of connected sockets The communication is bidirectional input to the UNIX process is relayed to the Self process over the socket connection and output produced by the Self process is sent over the same socket connection to the UNIX process which relays it to stdout The right part of Figure 5 shows how the UNIX Self process pair can fit seamlessly into a pipe line Source code that facilitates setting up such UNIX Self process pairs is included in the Self distribution The source consists of two parts one being a Self program called server the other being a C program called toself When the server is started it creates a socket binds a name to it and then listens for connections on it toself establishes connections to the server program The first line that is transmitted when a connection has been set up goes from toself to the server The line contains a Self expression Upon receiving it the server forks a new process to evaluate the expression in the context of the lobby augmented with a slot stdio that
227. value if block s argument is evaluated 140 Chapter 10 Appendices Self Handbook Documentation Release 2 for Self 4 4 Basic looping loop loopExit loopExitValue repeat the block forever repeat the block until argument is evaluated then exit and return nil repeat the block until argument is evaluated then exit and return a value Pre test looping whileTrue whileFalse whileTrue whileFalse repeat the receiver until it evaluates to true repeat the receiver until it evaluates to false repeat the receiver and argument until receiver evaluates to true repeat the receiver and argument until receiver evaluates to false Post test looping untilTrue repeat the receiver and argument until argument evaluates to true untilFalse repeat the receiver and argument until argument evaluates to false Iterators do iterate passing each element to the argument block to By Do iterate with stepping to Do iterate forward upTo By Do iterate forward without last element with stepping upTo Do iterate forward without last element downTo By Do reverse iterate with stepping downTo Do reverse iterate Collections Sizing isEmpty test if collection is empty size return number of elements in collection Adding add add argument element to collection receiver addAll add all elements of argument to receiver at Put add key value pair at Put IfAbsent add key value pair evaluat
228. version of the compiler will recompile and reoptimize frequently used code using information gathered at run time as to how the code is being used see HCU91 for details Don t be misled by the term compiled method if you are familiar with Smalltalk in Smalltalk terminology it denotes a method in its bytecode form but in Self it denotes the native machine code form In Smalltalk there is only one compiled method per source method but in Self there may be several different compiled methods for the same source method because of customization 4 Chapter 1 Introduction CHAPTER TWO LANGUAGE REFERENCE This chapter specifies Self s syntax and semantics An early version of the syntax was presented in the original Self paper by Ungar and Smith US87 this chapter incorporates subsequent changes to the language The presentation assumes a basic understanding of object oriented concepts The syntax is described using Extended Backus Naur Form EBNF Terminal symbols appear in Courier and are enclosed in single quotes they should appear in code as written not including the single quotes Non terminal symbols are italicized The following table describes the metasymbols META SYMBOL FUNCTION DESCRIPTION and grouping used to group syntactic constructions and option encloses an optional construction and repetition encloses a construction that may be repeated zero or more times alternative separat
229. vide a border of empty space around their contents frameMorph Like a columnMorph except that it can display various kinds of borders around its contents Bezeled frameMorphs are used heavily in the programming environment to provide a three dimensional look spacerMorph While many types of morph such as an empty rowMorph could be used to fill a space between morphs it is preferable to use a spacerMorph to make it clear that the only purpose of the morph is to control spacing Morphic allows users to customize the user interface by directly manipu lating morphs Thus just as is it important to write readable programs it is important to build composite morphs with readable structure Often a spacerMorph is used to provide a fixed amount of space be tween submorphs in a rowMorph or columnMorph To accomplish this the spacerMorph should be of the desired width be rigid horizontally and space filling vertically and be the same color as the row Morph The message copyH Color or copyV Color to creating a vertical spacer for use in a column can be sent to spacerMorph to create a new spacerMorph with these properties The other common use of spacerMorphs is to provide a stretchy space between morphs the expression spacerMorph copy beFlex ible makes a spacerMorph that does the job Setting the baseMinWidth or baseMinHeight of such a spacer ensures that at least the given amount of space will be provided Other morphs supply de
230. w module Finally the non copied down slots in the prototype and traits objects are assigned to the module This may sound tedious but the system provide several shortcuts to accelerate the process To set the module for the new morphs home slot invoke Show annotation on the ovalMorph slot in the globals object type ovalMorph in the module field and accept the change Figure 11 Since this is a new module the system will ask whether a new module should be created yes whether it should be a submodule of an existing module no and what subdirectory it should be stored into applications Set the module of the ovalMorph slot in the traits object the same way All the slots in an object or within one category of that object can be assigned to a module in a single operation To assign the slots of the new traits object to the new module invoke the Set module command on the header of its outliner The system will ask which slots should be assigned to the module all and which module to put them into ovalModule After a few seconds the module summary at the top of the outliner should update to indicate that all slots of the traits object are in ovalModule Repeat this procedure to assign all the slots of the ovalMorph prototype to ovalModule Now that all the slots of the new morph and its prototype have been assigned to the new module the module can be filed out Invoke the Changed modules command on the
231. ways describe the interrelationship between traits objects In most cases leaf traits are concrete and have an associated prototype with the same name orderedOddball number float integer smallInt bigInt traits number defines behavior common to all numbers such as successor succ predecessor pred absoluteValue negate double half max and min traits number inherits from traits orderedOddball so sending copy or clone to a number returns the number itself traits integer de fines behavior common to all integers such as even odd and factorial There are four division operators for integers that allow the programmer to control how the result is truncated or rounded Integers also include behavior for iterating through a subrange including to Do CosByiDOs to ByNegative Do 3 4 Numbers and Time 27 Self Handbook Documentation Release 2 for Self 4 4 upTo Do upTo By D0 downTo Do downTo By Do Relevant oddballs e infinity IEEE floating point infinity e minSmallInt smallest smallInt in this implementation e maxSmallInt biggest smallInt in this implementation Modules number float integer smallInt bigInt 3 4 1 Random Numbers clonable random randomLC prototypes random Traits random defines the abstract behavior of random number generators A random number generator can be used to generate random booleans integers floats characters or strings traits randomLC defines a concrete special
232. x in the object and its ancestors Discards cached state e g the result of an enumeration On a module morph removes it from the list of changed modules and clears out its record of added changed amp removed slots On a module morph summons the object outliner for the module Useful for editing its postFileIn method or its revision Evaluate the selected text amp show the result Evaluate the text in the editor show the result Hides the object or slot annotation Hides the object or slot comment Searches for slots of a given name For an assignable slot x show all implementors of x Reads in a file created with the right menu item Save Morph to File On a slot set the creator annotation of its contents to be the slot Change the style of the slot to show that it is intended to be private not enforced Change the style of the slot to show that it is intended to be public not enforced Adds a comment for posterity Change the style of the slot to show that no clear intention exists as to its visibility A Self exclusive Searches for all methods containing a string Moves slots or categories Summon a new shell object Continued on next page 10 6 Every Menu Item in the Programming Environment 145 Self Handbook Documentation Release 2 for Self 4 4 Table 10 2 continued from previous page Open Factory Win dow Palette Paste Quit Radar View Read Module References
233. y keyed collections Iteration can be done with do or with variations that allow the programmer to specify special handling of the first and or last element with Do allows pairwise iteration through two collections The includes occurrencesOf and findFirst IfPresent IfAbsent messages test for the presence of particular values in the collection filterBy Into creates a new collection including only those elements that satisfy a predicate block while mapBy Into creates a new collection whose elements are the result of applying the argument block to each element of the original collection Abstract collection behavior is defined in traits collection Only a small handful of operations need be imple mented to create a new type of collection the rest can be inherited from traits collection See the descendantResponsibility slot of traits collection The following sections discuss various kinds of collection in more detail Modules collection abstract collection behavior 3 5 1 Indexable Collections collection indexable mutableIndexable byteVector the string hierarchy sequence sortedSequence vector Indexable collections allow random access to their elements via keys that are integers All sequences and vectors are indexable The message at is used to retrieve an element of an indexable collection while at Put is used to update an element of a mut ableIndexab1e collection other than a sortedSequence Modules indexab
234. y method s evaluation is the value returned by the non local return For example in the following method assertPositive x x gt 0 ifTrue ok Je error non positive x 8 Chapter 2 Language Reference Self Handbook Documentation Release 2 for Self 4 4 the error message will not be sent if x is positive because the non local return of ok causes the assertPositive method to return immediately 2 1 9 Construction of object literals Object literals are constructed during parsing the parser converts objects in textual form into real Self objects An object literal is constructed as follows e First the slot initializers of every slot are evaluated from left to right If a slot initializer contains another object literal this literal is constructed before the initializer containing it is evaluated If the initializer is an expression it is evaluated in the context of the lobby e Second the object is created and its slots are initialized with the results of the evaluations performed in the first step Slot initializers are not evaluated in the lexical context since none exists at parse time they are evaluated in the context of an object known as the Lobby That is the initializers are evaluated as if they were the code of a method in a slot of the Lobby This two phase object construction process implies that slot initializers may not refer to any other slots within the constructed object as with
235. y storage by the compiler and by primitives C Heap Number of bytes allocated on the C heap by Self excluding the memory and code spaces and the resource area The memory status portion of the system monitor consists of bars representing memory spaces and their utilization all bars are drawn to scale relative to one another their areas being proportional to the actual sizes of the memory spaces The next table explains the details of this part of the system monitor s display Table 7 The system monitor display memory status Space Description object memory The four or more bars represent from top to bottom eden the two survivor spaces and subsequent bars are segments of old space The left and right parts of each bar represent the space used by plain objects and byte vectors respectively The above picture shows a situation in which about half of old space is filled with plain objects and about 25 is filled with byte vectors A fraction of old space s used portions is currently paged out gray areas Below the old space is a ruler marked in 1Mb intervals showing the total allocated in old space extending line at the left To the right is a red bar representing how much of old space is reserved for use by the Virtual Machine and a yellow bar representing the low space threshold when crossed the scheduler is notified and a garbage colelction may take place code cache These four bars represent the cache holdin
236. zeError bad 4 5 TypeError bv_null ptr_type byte vector O ptr_type badTypeError 4 6 bv_len_null ptr_type byte vector O ptr_type int badSizeError bad 4 5 6 TypeError cbv ptr_type byte vector ptr_type badTypeError 7 cbv_len ptr_type byte vector ptr_type int badSizeError bad 7 TypeError cbv_null ptr_type byte vector O _ ptr_type badTypeError 7 cbv_len_null ptr_type byte vector O0 ptr_type int badSizeError bad 7 TypeError string byte vector char badTypeError 8 nullCharError string_len byte vector char int badTypeError 5 8 nullCharError string_null byte vector O char badTypeError 6 8 nullCharError string_len_null byte vector 0 char int badTypeError 5 6 8 nullCharError proxy ptr_type proxy ptr_type badTypeError bad 9 type_seal NULL TypeSealError deadProxyEr ror nullPointerError proxy_null ptr_type proxy ptr_type badTypeError bad 9 type_seal TypeSealError deadProxyError any_oop any object oop 10 oop oop subtype corresponding oop subtype badTypeError 11 object any C C type int float proxy bytet float ptr ptr badIndexError 12 vector int badTypeError dead ProxyError 1 The C type char has a system dependent range Either 0 255 or 128 127 A WY N Precision may be lost in the conversion The type smi is used internally in the virtual machine a 30 bit integer The second part of the conversion is a C pointer type The address of the first byte in the byte vector

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