PLT DrScheme: Programming Environment Manual
Contents
1. and put the insertion point in the arglist of the lambda 21 Keybindings menu item 14 keyboard shortcuts 19 Kill menu item 15 language levels see languages languages 4 changing 4 extending 24 launcher executables 8 libmred vers dll 8 libmzgc vers dll 8 libmzsch vers dll 8 license 27 Log Definitions and Interactions menu item 13 Map delete to backspace preference 18 memory requirements 27 menu items 13 Module Browser menu item 15 module language 5 Most Recent Window menu item 17 MrFlow 28 MrSpidey 28 multimedia file format 22 New menu item 13 Number of recent items preference 18 numbers 34 printing 7 Only warn once when executions and interactions are not synchronized preference 18 Open Recent menu item 13 Open menu item 13 output format 9 overwrite mode 21 Parenthesis highlight color preference 18 Paste menu item 14 plain text file format 21 PLT Graphical MrEd language 5 PLT Pretty Big language 5 PLT Textual MzScheme language 5 plt prefs ss 22 23 PLT_MrEd 8 PLT_MzScheme 8 PLTDRCM 25 PLTDRDEBUG 26 PLTDRTESTS 26 PLTHDCM 25 PLTNOTOOLS 25 PLTONLYTOOL 25 PLTSTRINGCONSTANTS 26 preference files 22 preferences 17 site specific 22 Preferences menu item 14 Print Definitions menu item 13 Print Interactions menu item 13 printing format 9 proxy 19 28 quasiquote style output 9 R5RS 5 read 10 read char 102. 14 Hide Interactions menu item 14 INDEX Hide Profile menu item 14 Hide Program Contour menu item 14 Highlight between matching parens preference 18 I O 10 Indenting preferences 17 indenting Scheme code 4 Insert Comment Box menu item 16 Insert Delta define menu item 16 Insert Fraction menu item 16 Insert Image menu item 16 Insert Java Comment Box menu item 16 Insert Java Interactions Box menu item 16 Insert Lambda menu item 16 Insert Large Letters menu item 16 Insert Scheme Box menu item 16 Insert Scheme Splice Box menu item 16 Insert Test Case menu item 16 Insert XML Box menu item 16 Install PLT File menu item 13 installation instructions 28 Interact with DrScheme in English menu item 17 interactions window 2 4 Intermediate Student language 5 Intermediate Student with Lambda language 5 keybindings 19 A C down 20 A C left 20 A C right 20 A C up 20 b 21 C 21 C _ 21 C a 19 C b 19 C d 20 C x C s 21 C x C w 21 C x u 21 C y 20 copy selection to clipboard 20 cut complete sexpression 20 delete backward one character 20 delete backward one word 20 delete forward one character 20 delete forward one S expression 20 delete forward one word 20 delete forward to end of line 20 delete selection to clipboard cut 20 Execute 21 f5 21 M lt 19 M gt 19 M 20 M 20 M 21 M b 19 M C b 20 M C d 20 M C down 20
3. M C f 20 M C k 20 M C left 20 M C m 20 M C p 20 M C right 20 M C SPACE 20 M C t 20 M C u 20 M C up 20 M d 20 M DEL 20 M f 19 M n 21 M o 21 M p 21 M S L 21 M t 20 M v 19 M w 20 match parentheses backward 20 move backward one character 19 move backward one page 19 move backward one S expression 20 move backward one word 19 move backwards to the nearest editor box 20 move down into a nested S expression 20 move down into an embedded editor 20 move forward one character 19 move forward one page 19 move forward one S expression 20 move forward one word 19 move forward to the nearest editor box 20 move to beginning of file 19 move to beginning of line left 19 33 INDEX move to end of file 19 move to end of line right 19 move to next line down 19 move to previous line up 20 move up out of an embedded editor 20 move up out of an S expression 20 paste from clipboard yank 20 redo 21 save file 21 save file under new name 21 search for string backward 21 search for string forward 21 select forward S expression 20 toggle dark green marking of matching paren thesis 20 toggle overwrite mode 21 transpose characters 20 transpose sexpressions 20 transpose words 20 undo 21 wrap selection in curly brackets 21 wrap selection in parentheses 20 wrap selection in square brackets 20 wrap selection in lambda
4. read eval print loop 9 recycling icon 2 Redo menu item 14 Reindent All menu item 15 Reindent menu item 15 Related Web Sites menu item 17 Replace amp Find Again menu item 14 Reuse existing frames when opening new files pref erence 18 Revert menu item 13 Save button 3 Save Definitions As Text menu item 13 Save Definitions As menu item 13 Save Definitions menu item 13 INDEX Save Interactions As Text menu item 13 Save Interactions As menu item 13 Save Interactions menu item 13 Save Other menu item 13 Search in Files menu item 13 Select All menu item 14 Show Definitions menu item 14 Show Interactions menu item 14 Show Profile menu item 14 Show Program Contour menu item 14 Show status line preference 18 Split menu item 15 stand alone executables 8 30 status line 2 Step button 3 stepper 3 storage requirements 28 supported platforms 27 tail calls 3 Teachpacks implementing 24 Test Suite Window 11 The Stepper 3 Tool Web Sites menu item 17 tools 24 Uncomment menu item 16 Undo menu item 14 Use separate dialog for searching preference 18 Verify exit preference 18 Wrap Text menu item 14 Wrap words in editor buffers preference 18 write 10 XML 11 yellow and black messages 29 35
5. 27 2 Quasiquote style Outpt s saa asa a aaa a E EA ee ees 28 Input and Um 2 0 24 444954 6545 see bbe daa Eaa E a Interface Reference 3 1 Menus 3 1 1 Language Scheme Special Windows 10 11 11 13 13 13 14 14 15 15 16 17 CONTENTS CONTENTS US HS aa as e AAA A a eS ee Ae be 8 17 o AAA 17 33 Weyboatd Shoricuts o ss aia AAA A A A 19 SL Moyne Around 4 2444422484 040 aus bo a dd bes 19 ga Editing OPERONS es rc a ae ER ee eo Boe ae ee RRR Rw 20 aoe Wile IPRC see a ae A Se ee a eed e 21 Ace TOC cis SR A he OR OS we ROR IR A Bae OE a 21 Ooo Miscellaneous s o s tena ek eae He EEE AAA we NS 21 a A a ae 3 4 0 tn Coe eee eee hdd ee ee ERG Eee P a4 21 Sa DWrScheme Piles ey cece a eee ee eS PERERA ERE See ee Ce a eg 21 Gil A Sle Gs os SS Hes ee A A ea a ee ee Be we 21 3 4 2 Backup and Autosave Files ce a siaaa a aama ee 22 wo Preferentes Piles coso a a OS EE A Bok me ew 22 4 Extending DrScheme 24 Hl Tea PGiGke ae gy gg Ga AR Oe eS a a a ee a eee SS Sok ee eG 24 Moo LOIS oe os Saath ROE SE EDD Ge ee Oe eae ER EAE ES 25 4 0 Environment Variables s ii ess sa ee EN PO ee eee eA He E 25 5 Frequently Asked Questions 27 5 1 Supported Operating Systems and Installation 0 02 000004 27 5 2 Using Drscheme osorno A 28 bo Memory and Pertoraiadide cosas rara SEEAR SEES Pewee eee eee oe 4 30 Be Troubles OO LR bao 6 a Se ee a A Se ae oe BO ew 30 Index 32 1
6. Check for Updates Opens an internet connection to check if there have been any updates to various installed DrScheme packages e Related Web Sites This submenu has a list of related web sites Choosing one of them sends a message to an external browser to visit the web site e Tool Web Sites This submenu has a list of web sites for the add on tools in your DrScheme Choosing one of them sends a message to an external browser to visit the web site e Interact with DrScheme in English This and the related menu items at the end of the Help menu switch DrScheme s interface natural language 3 2 Preferences The preferences dialog comprises several panels e Font This panel controls the main font used by DrScheme e Syntax Coloring The Syntax Coloring panel has several subpanels that enable you to configure the colors that DrScheme uses for its online coloring and for Check Syntax e Editing The Editing panel consists of several sub panels Indenting This panel controls which keywords DrScheme recognizes for indenting and how each keyword is treated 17 3 2 Preferences 3 Interface Reference 18 General x x Number of recent items controls the length of the Open Recent menu in the File menu Auto save files If checked the editor generates autosave files see drscheme autosave files for files that have not been saved after five minutes Backup files If checked when saving a file for the
7. DrScheme For example a step might replace 1 2 with 3 These are the same rules used by DrScheme to evaluate a program Clicking Step opens a new window that contains the program from the definitions window plus three new buttons Next Previous and Home Clicking Next performs a single evaluation step clicking Previous retraces a single step and clicking Home returns to the initial program The Stepper works only for programs using the Beginning Student language level Clicking the Check Syntax button annotates the program text in the definitions window It add these annotations e Syntactic Highlighting Imported variables and locally defined variables are highlighted with color changes e Lexical Structure The lexical structure is shown with arrows overlaid on the program text When the mouse cursor passes over a variable DrScheme draws an arrow from the binding location to the variable or from the binding location to every bound occurrance of the variable Additionally control or right button mouse clicking on a variable activates a popup menu that lets you jump from binding location to bound location and vice versa a rename the variable or tack the arrows so they do not disappear e Tail Calls Any subexpression that is syntactically in tail position with respsect to its enclosing context is annotated by drawing a light purple arrow from the tail expression to its surrounding expression e Require Annotations Control clicking
8. Student teaching language and more It is useful as a step past Advanced Student or for implementing MrEd programs with a richer base syntax and set of primitives Note that there some forms for example define struct that appear in both Advanced and MrEd but with slightly different semantics In all such cases the PLT Pretty Big language uses the forms from the MrEd language In the case of define struct Advanced implicitly uses a very permissive inspector see inspectors for details and MrEd uses the current inspector e module requires that the definitions window contain only a single module declaration as defined in PLT MzScheme Language Manual The module explicitly declares the language for the module s body The Language Choose Language dialog contains a Show Details button for configuring certain details of the language specification Each option corresponds to one of the lines in the language table but only a few of the lines in the figure have an option in the dialog Whenever the selected options do not match the default language specification a Custom indicator appears next to the language selection control at the top of the dialog The teaching languages differ from conventional Scheme in a number of ways e Case sensitive identifiers and symbols In a case sensitive language the variable names x and X are distinct and the symbols x and X are also distinct In a case insensitive language x and X are equiva
9. escape back to constructor style printing for non lists and non symbols With quasiquote style printing the above example prints as 2 8 Input and Output 2 Interface Essentials lambda x lambda y x y This example list lambda list x box lambda y x y in quasiquote style printing prints as lambda x box lambda y x y 2 8 Input and Output Many Scheme programs avoid explicit input and output operations obtaining input via direct function calls in the interactions window and producing output by returning values Other Scheme programs explicitly print output for the user during evaluation using write or display or explicitly request input from the user using read or read char Explicit input and output appear in the interactions window but within special boxes that separate explicit I O from normal expressions and results For example evaluating gt read in the interactions window produces a special box for entering input The underscore indicates the location of the flashing caret Type an number into the box and hit Enter and that number becomes the result of the read expression If you type 5 the overall interaction appears as follows gt read 5 5 gt The mouse cursor becomes a watch whenever DrScheme is evaluating expression but you can still use the mouse to move the selection in an input box Output goes to the same b
10. first time in each editing session the original copy of the file is copied to a backup file in the same directory The backup files have the same name as the original except that they end in either bak or x Map delete to backspace If checked the editor treats the Delete key like the Backspace key x Show status line If checked DrScheme shows a status line at the bottom of each window x Count column numbers from one If checked the status line s column counter counts from one Otherwise it counts from zero Display line numbers in buffer not character offsets If checked the status line shows a line column display for the current selection rather than the character offset into the text Wrap words in editor buffers If checked DrScheme editors auto wrap text lines by default Changing this preference affects new windows only Use separate dialog for searching If checked then selecting the Find menu item opens a separate dialog for searching and replacing Otherwise selecting Find opens an interactive search and replace panel at the bottom of a DrScheme window Reuse existing frames when opening new files If checked new files are opened in the same DrScheme window rather than creating a new DrScheme window for each new file Enable keybindings in menus If checked some DrScheme menu items have keybindings Otherwise no menu items have key bindings This preference is designed for people who are comfo
11. starts It also accesses library files from your DrScheme installation when it runs Since a launcher executable contains specific paths to access those files launchers usually cannot be moved from one machine to another e A stand alone executable tends to be large because it embeds a copy of your program at the time that it is created as well as any library that your code uses When the executable is started it uses the embedded copies and does not need your original source file or your DrScheme installation It may however require DLLs or framework libraries installed on your machine depending on your operating system Windows The executable requires the following DLLs libmzsch vers dll libmzgc vers dll and for executables using the MrEd engine libmred vers dll where vers is based on the current version number These DLLs are normally installed in the system directory Mac OS X The executable requires the PLT_MzScheme framework which is normally in stalled in Library Frameworks When using the MrEd engine the executable also requires the PLT_MrEd framework from the same location To move the stand alone executable to another machine the DLLs or frameworks that it uses must also be copied to the other machine You can download these DLLs or frameworks as a separate package from http www plt scheme org software dynamic libraries or you can just copy them into the places manually DrScheme may a
12. the Control Meta or Command key C key This means press the Control key hold it down and then press key and then release them both For example C e Control E moves the blinking caret to the end of the current line M key Same as C key except with the Meta key Depending on your keyboard Meta may be called Left Right or have a diamond symbol but it s usually on the bottom row next to the space bar M key can also be performed as a two character sequence first strike and release the Escape key then strike key Under Windows and Mac OS Meta is only available through the Escape key DEL The Delete key SPACE The Space bar Note On most keyboards lt and gt are shifted characters So to get M gt you actually have to type Meta Shift gt That is press and hold down both the Meta and Shift keys and then strike gt Note Many of the key bindings can also be done with menu items Under Windows some of these keybindings are actually standard menu items Those keybindings will behave according to the menus unless the Enable keybindings in menus preference is unchecked If you are most familiar with Emacs style key bindings you should uncheck the Enable keybindings in menus preference Many of the keybindings below are inspired by Emacs 3 3 1 Moving Around e C f move forward one character e C b move backward one character M f move forward one word e M b move backward one word
13. About DrScheme DrScheme is a graphical environment for developing programs using the Scheme programming language DrScheme runs under Windows 95 and up Mac OS and Unix X 2 Interface Essentials The DrScheme window has three parts a row of buttons at the top two editing panels in the middle and a status line at the bottom DrScheme File Edit Show Language Scheme Windows Help menus ae Save Check Syntax Step Execute Break buttons 33 Square number gt number to produce the square of x define square x x x definitions window Welcome to DrScheme version 200 Language Beginning Student gt square 2 4 interactions window gt 5 2 Unlocked not running status line The top editing panel called the definitions window is for defining Scheme programs The above figure shows a program that defines the function square The bottom panel called the interactions window is for evaluating Scheme expressions interactively The Language line in the interactions window indicates which primitives are available in the definitions and interactions windows In the above figure the language is Beginning Student which is the default language Clicking the Execute button evaluates the program in the definitions window making the program s defi nitions available in the interactions window Given the defi
14. Beginning Student through Advanced Student languages the boolean combination forms require at least two sub expressions This restriction helps detect missing or ill formed sub expressions in a Boolean expression 2 Interface Essentials 2 5 Languages e set disallowed on arguments In the Advanced Student language set cannot be used to mutate vari ables bound by lambda This restriction ensures that the substitution model of function application is consistent with DrScheme s evaluation e Improper lists disallowed A proper list is either an empty list or a list created by consing onto a proper list In the Beginning Student through Advanced Student languages cons constructs only proper lists signaling an error if the second argument is not a proper list Since beginning students do not need improper lists this restriction help detect logical errors in recursive functions e Dot is diallowed In the Beginning Student through Advanced Student languages a delimitted period is disallowed e g as an improper list constructor in a quoted form or for defining multi arity procedures e Keywords disallowed as variable names In the Beginning Student through Advanced Student lan guages all syntactic form names are keywords that cannot be used as variable names e Re definitions are disallowed In the Beginning Student through Advanced Student languages top level names can never be re defined e Function definitions a
15. Language menu item 15 Clear All Teachpacks menu item 15 Clear Error Highlight menu item 15 Clear menu item 14 Close menu item 13 Collapse menu item 15 Color syntax interactively preference 18 Comment Out with a Box menu item 16 Comment Out with Semicolons menu item 16 compiler 29 configuration files 22 constructor style output 9 Copy menu item 14 Correct parens preference 18 32 Count column numbers from one preference 18 Create Executable menu item 15 Create Servlet menu item 15 Cut menu item 14 defaults site specific 22 defaults 23 definitions window 2 Delete menu item 14 Disable All Test Cases menu item 16 disk requirements 28 display 10 Display line numbers in buffer not character off sets preference 18 DLLs 8 documentation downloading 27 DrScheme Environment Variables 25 DrScheme Teachpacks 24 editors 3 Emacs keybindings 19 Enable keybindings in menus preference 18 error highlighting 4 evaluating expressions 4 Execute button 4 Execute menu item 15 execution speed 30 file extensions 21 filename button 2 Find Again menu item 14 Find menu item 14 18 Flash paren match preference 18 flashing parenthesis matches 3 font preference 17 formatting Scheme code 4 frequently asked questions 27 graphical interface 2 details 13 gray highlight regions 3 Help Desk 28 Help Desk menu item 17 Help menu item 17 Hide Definitions menu item
16. PLT DrScheme Programming Environment Manual PLT scheme plt scheme org 206 1 Released January 2004 Copyright notice Copyright 1996 2003 PLT Permission to make digital hard copies and or distribute this documentation for any purpose is hereby granted without fee provided that the above copyright notice author and this permission notice appear in all copies of this documentation Send us your Web links If you use any parts or all of the PLT Scheme package software lecture notes for one of your courses for your research or for your work we would like to know about it Furthermore if you use it and publicize the fact on some Web page we would like to link to that page Please drop us a line at scheme plt scheme org Evidence of interest helps the DrScheme Project to maintain the necessary intellectual and financial support We appreciate your help Thanks This manual was typeset using TX SATEX and tex2page Some typesetting macros were originally taken from Julian Smart s Reference Manual for wrWindows 1 60 a portable C GUI toolkit This manual was typeset on February 9 2004 Contents 1 About DrScheme 2 Interface Essentials 3 2 1 Butt ns s ses 2 2 The Editor 23 The Interactions Window 446 4 404 040 c8 5 402 644864 ee 4444 oad eee 2 4 Errors 2 5 Languages 2 6 Executables 2 7 Printed Results Beel Constructorstyle Output oo c sa aa easa s aa Poe a a a aa ee E a
17. age corresponding to one of the files in plt collects string constants it only shows the unset string constants matching that language This environment variable must be set when zo files are made To ensure that you see its output properly run setup plt with the c option set the environment variable and then run setup plt again 26 5 Frequently Asked Questions 5 1 Supported Operating Systems and Installation Where can I get DrScheme and or documentation DrScheme is available for download at http www drscheme org Some documentation is provided with DrScheme accessible through Help Desk Other documentation is provided online in HTML format and is also available for download in Adobe PDF format at http download plt scheme org doc How much does DrScheme cost DrScheme is absolutely free for anyone to use However there are restrictions on the way that DrScheme can modified and redistributed Please read the GNU Library General Public License in the distribution for details What operating systems are supported for DrScheme Windows 95 and up Mac OS X and Unix with the X Window System How much memory is needed to run DrScheme To run DrScheme comfortably your machine should have at least 128 MB of RAM I don t have that much memory Are there any other PLT options MrEd is PLT s raw graphical Scheme implementation used to execute DrScheme MrEd provides a minimal read eval print loop but MrEd doe
18. and Mac OS a pound sign is added to the start and end of the file s name then a number is added after the ending pound sign and then one more pound sign is appended to the name The number is selected to make the autosave filename unique e Under Windows the file s extension is replaced with a number to make the autosave filename unique 3 4 3 Preference Files On start up DrScheme reads configuration information from a preferences file The name and location of the preferences file depends on the platform and user e Under Unix preferences are stored in plt prefs ss in the user s home directory e Under Windows if the HOMEDRIVE and HOMEPATH environment variables are defined preferences are stored in 7 HOMEDRIVE HOMEPATH plt prefs ss otherwise preferences are stored in plt prefs ss in the directory containing the MrEd executable Windows NT XP 2000 When DrScheme is launched under Windows NT XP or 2000 and HOMEDRIVE and HOMEPATH are not set Windows automatically sets the variables to indicate the root directory of the main disk Therefore when HOMEDRIVE and HOMEPATH are not set the preferences file plt prefs ss is saved in the root directory of the main disk e Under Mac OS X preferences are stored in plt prefs ss in the user s preferences folder Under Mac OS Classic preferences are stored in plt prefs ss in the system preferences folder A lock file is used while modifying the preferences file in the same d
19. be of the form identifier This restriction helps detect confusing misuses of parentheses such as 1 or 3 4 which is a common mistake among beginners who are used to the optional parentheses of algebra e Top level required at function call position In the Beginning Student languages procedure calls must be of the form top level identifier and the number of actual arguments must match the number of formal arguments if top level identifier is defined This restriction helps detect confusing misuses of parentheses such as x where z is a function argument DrScheme can detect such mistakes syntactically because Beginning Student does not support higher order procedures e Primitive and defined functions allowed only in function call position In Beginning Student lan guages the name of a primitive operator or of a defined function can be used only after the open parenthesis of a function call except where teachpack extensions allow otherwise as in the convert gui extension Incorrect uses of primitives trigger a syntax error Incorrect uses of defined names trigger a run time error DrScheme can detect such mistakes because Beginning Student does not support higher order procedures e lambda allowed only in definitions In the Beginning Student through Intermediate Student lan guages lambda or case lambda may appear only in a definition and only as the value of the defined variable e Free variables are not a
20. d by let Lt list 0 list lt It prints as shared 1 list 0 list 1 1 instead of list list 0 list 0 2 6 Executables 2 Interface Essentials 2 6 Executables DrScheme s Create Executable menu lets you create an executable for your program that you can start without first starting DrScheme To create an executable first save your program to a file and set the language and teachpacks Click Execute just to make sure that the program is working as you expect Beware the executable you create will not have a read eval print loop so be sure to have an expression that starts your program running in the definitions window before creating the executable Once you are satisfied with your program choose the Create Executable menu item from the Scheme menu Choose a place to save the executable You will be able to start the saved executable in the same way that you start any other program on your computer An executable created by Create Executable is either a launcher executable or a stand alone executable and it uses either a graphical MrEd or textual MzScheme engine For programs implemented with certain languages Create Executable will prompt you to choose the executable type and engine while other languages support only one type or engine Each type has advantages and disadvantages e A launcher executable tends to be small and it uses the latest version of your program source file when it
21. d select it through the Languagel Add Teachpack menu item e A tool extends the set of utilities within the DrScheme environment For example DrScheme s Check Syntax button starts a syntax checking tool and the Analyze button starts the MrSpidey tool 4 1 Teachpacks Teachpacks are designed to supplement student programs with code that is beyond the teaching languages Beginning Student Intermediate Student Advanced Student For example to enable students to play hangman we supply a teachpack that e implements the random choosing of a word e maintains the state variable of how many guesses have gone wrong e manages the GUI All these tasks are beyond students in the third week and or impose memorization of currently useless knowledge on students The essence of the hangman game however is not The use of teachpacks enables the students to implement the interesting part of this exercise and still be able to enjoy today s graphics without the useless memorization A single Scheme source file defines a teachpack although the file may access other files via require The file must contain a module according to the naming convention laid out in the MzScheme manual the name of the file must be the name of the module with an additional scm or ss extension on the filename Each exported syntax definition or value definition from the module is provided as a new primitive form or primtive operation to the user respectively As an
22. e C v move forward one page e M v move backward one page e M lt move to beginning of file e M gt move to end of file e C a move to beginning of line left e C e move to end of line right 19 3 3 Keyboard Shortcuts 3 Interface Reference e C n move to next line down e C p move to previous line up e M C f move forward one S expression e M C b move backward one S expression e M C u move up out of an S expression e M C d move down into a nested S expression e M C SPACE select forward S expression e M C p match parentheses backward e M C left move backwards to the nearest editor box A C left move backwards to the nearest editor box M C right move forward to the nearest editor box A C right move forward to the nearest editor box e M C up move up out of an embedded editor e A C up move up out of an embedded editor e M C down move down into an embedded editor e A C down move down into an embedded editor 3 3 2 Editing Operations C d delete forward one character C h delete backward one character M d delete forward one word M DEL delete backward one word C k delete forward to end of line M C k delete forward one S expression M w copy selection to clipboard C w delete selection to clipboard cut C y paste from clipboard yank C t transpose characters e M t transpose words e M C t transpose sexpressions e M C m toggle dark green marking of matching parenthesis e M C k cut com
23. em in the Edit menu Can I change the key bindings in DrScheme Technically yes but that requires in depth information about the way that DrScheme is implemented The necessary information is part of the MrEd toolbox manual DrScheme currently provides no simple way to adjust the keyboard mappings other than to set the behavior of the Delete key via the preferences dialog What do those yellow and black messages mean and how do I get rid of them When text in the definitions window is modified the current language is changed or the current library is changed DrScheme pessimistically assumes that some definition has been changed In this case expressions evaluated in the interaction window would use definitions that do not match those currently displayed in the definitions windows A yellow and black message warns you about this potential inconsistency and suggests that you resolve the inconsistency by clicking the Execute button To suppress all but the first warning see the Warnings tab in the Preferences dialog Why can t I type in the interaction window before the the current prompt To prevent accidental revisions of the interaction history DrScheme disallows editing before the current prompt While old expressions cannot be edited in place you can copy old expressions to the current prompt by typing Esc p Alternatively place the insertion caret at the end of any old expression in the interactions window and type Enter or Re
24. eme to evaluate the expression by typing alt return or command return depending on your platform To copy the previous expression to the current prompt type ESC p i e type Escape and then type p Type ESC p multiple times to cycle back through old expressions Type ESC n to cycle forward through old expressions Clicking the Execute button evaluates the program in the definitions window and makes the program s definitions available in the interactions window Clicking Execute also resets the interactions window erasing all old interactions and removing old definitions from the interaction environment Although Execute erases old gt prompts ESC p and ESC n can still retrieve old expressions 2 4 Errors Whenever DrScheme encounters an error while evaluating an expression it prints an error message in the interactions window and highlights the expression that triggered the error The highlighted expression might be in the definitions window or it might be after an old prompt in the interactions window For certain kinds of errors DrScheme turns a portion of the error message into a hyperlink Click the hyperlink to get help regarding a function or keyword related to the error 2 5 Languages DrScheme supports multiple dialects of Scheme The name of the current evaluation language always ap pears in in the top of the interactions window To choose a different language select the Language Choose Language menu item After chang
25. enting attributes and remaining elements are the nested XML expressions XML boxes have two modes for handling whitespace In one mode all whitespace is left intact in the resulting xexpr In the other mode any tag that only contains nested XML expressions and whitespace has the whitespace removed You can toggle between these modes by right clicking or control clicking on the top portion of the XML box In addition to containing XML text XML boxes can also contain Scheme boxes Scheme boxes contain Scheme expressions These expressions are evaluated and their contents are placed into the containing XML box s xexpr There are two varieties of Scheme box the standard Scheme box and the splicing Scheme box The standard Scheme box inserts its value into the containing xexpr The contents of the splice box must evaluate to a list and the elements of the list are flattened into the containing xexpr Right clicking or control clicking on the top of a Scheme box opens a menu to toggle the box between a Scheme box and a Scheme splice box 2 10 Test Cases DrScheme also includes support for creating test cases as part of the program text This support is designed as an aid for students building tests as part of the How to Design Programs design recipes Test cases in DrScheme are written in special boxes To create one choose Insert Test Case from the Scheme menu in the DrScheme window The test cases consists of three editable areas From the t
26. es the different formats that DrScheme uses for printing results in the interactions window Each of the different settings here also apply to the print primitive That is printing in the interactions window is identical to output produced by the print primitive 2 7 1 Constructor style Output DrScheme s constructor style output treats cons vector and similar primitives as value constructors rather than functions It also treats list as shorthand for multiple cons s ending with the empty list Constructor style printing is valuable for beginning computer science students because output values look the same as input values Results printed in DrScheme s interactions window using constructor style printing look different than results printed in traditional Scheme implementations which use write to print results The table in Figure 2 1 shows the differences between values printed in constructor style and values printed with write 2 7 2 Quasiquote style Output Constructor style output is inconvenient for printing S expression results that represent programs For example the value lambda x lambda y x y prints as list lambda list x list lambda list y list x y with constructor style printing DrScheme s quasiquote style output combines the input output invariance of constructor style printing with the S expression readability of write It uses quasiquote to print lists and uses unquote to
27. example example the following teachpack provides a lazy cons implementation To test it be sure to save it in a file named lazycons scm module lazycons mzscheme provide rename lcons Icons Icar ledr define struct Icons hd tl 24 4 Extending DrScheme 4 2 Tools define syntax lcons stx syntax case stx _ hd exp tl exp syntax make lcons delay hd exp delay tl eap define Icar Icons force lcons hd Icons define Icdr Icons force Icons tl lcons Then in this program define Imap f 1 Icons f Icar 1 Imap f ledr 1 define all nums Icons 1 Imap add1 all nums the list all nums is bound to an infinite list of ascending numbers For more examples see the htdp directory of the teachpack directory in the PLT installation 4 2 Tools A separate manual describes the mechanism for defining a tool See PLT Tools DrScheme Extension Manual 4 3 This Environment Variables section lists the environment variables that affect DrScheme s behavior See the MzScheme manual 815 4 in PLT MzScheme Language Manual for general information about environment variables PLTNOTOOLS When this environment variable is set DrScheme doesn t load any tools PLTONLYTOOL When this environment variable is set DrScheme only loads the tools in the collection named by the value of the environment variable If the variable is bound to a parenthesized list of collections o
28. files in two formats text and multimedia The text format is the usual platform specific text format Tools for moving files between platforms typically support a text transfer mode that adjusts newlines and carriage returns in the test as appropriate The multimedia format used for saving files that contain pictures or formatted text is platform indepdendent Although no other program is able to read DrScheme s special format a multimedia format file can be moved between different platforms in binary mode and DrScheme will read it correctly on the destination platform 5 3 Memory and Performance Does DrScheme really require at least 128 MB of memory Yes Why do programs run more slowly in DrScheme than in other Scheme implementations in cluding PLT s own MzScheme Programs run more slowly in DrScheme because DrScheme inserts extra checks into a program to provide information about the location of run time errors For many languages these checks can be disabled by un checking Debugging in the details portion of the language selection dialog 5 4 Troubleshooting When I run DrScheme it is very slow and the disk is constantly running Why You do not have enough memory to run DrScheme If DrScheme works well for a while and then starts paging using the disk a lot then your memory configuration is borderline for DrScheme If DrScheme usually works well and has only suddenly started this bad behavior then per
29. h module The squares are colored based on the number of lines of code in the module If a module has more lines of code it gets a darker color In addition for each normal import a blue line drawn is from the module to the importing module Similarly purple lines are drawn for each for syntax import In the initial module layout modules to the left import modules to the right but since modules can be moved around interactively that property might not be preserved To open the file corresponding to the module right click on the box for that module control click under Mac OS Reindent Indents the selected text according to the standard Scheme formatting conventions Pressing the Tab key has the same effect Reindent All Indents all of the text in either the definitions or interactions window depending on the location of the selection or blinking caret 15 3 1 Menus 3 Interface Reference 66 99 Comment Out with Semicolons Puts characters at each of the the beginning of each selected line of text Comment Out with a Box Boxes the selected text with a comment box Uncomment Removes all characters at the start of each selected line of text or removes a comment 6 99 box around the text Uncommenting only removes a if it appears at the start of a line and it only removes the first on each line Disable All Test Cases Creates a new test case box see section 2 10 3 1 6 Special 16 I
30. haps you have written a program that consumes an infinite amount of memory I think I found a bug What should I do First read this section to make sure your problem does not have a standard answer If you need to submit a bug report using the form available from the home page of Help Desk Alternatively you may submit a bug report using the Web at http bugs plt scheme org 30 5 Frequently Asked Questions 5 4 Troubleshooting How do I send PLT a question If you have a question that is not answered in the documentation or this list of Frequently Asked Questions send mail to scheme plt scheme org 31 Index 18 define button 2 LOCK plt prefs ss 22 LOCKplt prefs ss 22 bak 18 22 plt prefs ss 22 sch 21 scm 21 Ss 21 Library Frameworks 8 gt prompt 4 About DrScheme menu item 17 Add Teachpack menu item 15 Advanced Student language 5 alpha renaming 3 Ask about clearing test coverage preference 18 Ask before changing save format preference 18 Auto save files preference 18 Automatically print to postscript file preference 18 autosave files 22 backup files 22 Backup files preference 18 Beginning Student language 4 Beginning Student language with List Abbrevia tions 5 Break button 3 Break menu item 15 Bring Frame to Front menu item 17 changing keybindings 29 Check for Updates menu item 17 Check Syntax 3 Choose
31. he find string and finds the next occurrence of the text that was last searched for Keybindings Shows all of the keybindings available in the current window Preferences opens the preferences dialog See section 3 2 In Mac OS X this menu item is under the apple menu 3 1 3 View One each of the following show hide pairs of menu items appears at any time 14 Show Definitions Shows the definitions window Hide Definitions Hides the definitions window Show Interactions Shows interactions window Hide Interactions Hides interactions window Show Program Contour Shows a 20 000 foot overview window along the edge of the DrScheme window Each pixel in this window corresponds to a letter in the program text Hide Program Contour Hides the contour window Show Profile Shows the current profiling report This menu is only useful if you have enabled profiling in the Language dialog Profiling does not apply to all languages When it does the checkbox that enables it is in the details portion of the dialog Hide Profile Hides any profiling information currently displayed in the DrScheme window 3 Interface Reference 3 1 Menus Note Split Splits the current window in half to allow for two different portions of the current window to be visible simultaneously Collapse If the window has been split before this menu item becomes enabled allowing you to collapse the split window whenever a program is executed the
32. ing the language click Execute to reset the language in the interactions window Five of DrScheme s languages are specifically designed for teaching 2 Interface Essentials 2 5 Languages Beginning Student is a small version of Scheme that is tailored for beginning computer science students Beginning Student with List Abbreviations is an extension to Beginning Student that prints lists with list instead of cons and accepts quasiquoted input Intermediate Student adds local bindings and higher order functions Intermediate Student with Lambda adds anonymous functions e Advanced Student adds mutable state The teaching languages different from conventional Scheme in a number of ways described below DrScheme also supports several languages for experienced programmers e Standard R RS contains those primitives and syntax defined in the R RS Scheme standard See the Revised Report on the Algorithmic Language Scheme for details e PLT Textual MzScheme extends RRS with exceptions threads objects modules components regu lar expressions TCP support filesystem utilities and process control operations See PLT MzScheme Language Manual for details e PLT Graphical MrEd extends MzScheme with a graphical toolbox for creating GUI applications with special support for editor applications hence the Ed in MrEd See also PLT MrEd Graphical Toolbox Manual e PLT Pretty Big extends MrEd with the forms of the Advanced
33. interactions window is made visible if it is hidden 3 1 4 Language Choose Language Opens a dialog for selecting the current evaluation language Click Execute to make the language active in the interactions window See section 2 5 for more information about the languages Add Teachpack Opens a find file dialog for choosing a teachpack to extend the current language Click Execute to make the teachpack available in the interactions windows See extending drscheme for information on creating teachpacks Clear All Teachpacks Clears all of the current teachpacks Click Execute to clear the teachpack from the interactions window In addition to the above menus there is a menu item for each teachpack that clears only that one teachpack 3 1 5 Scheme Execute Resets the interactions window and executes the program in the definitions window Break Breaks the current evaluation Kill Terminates the current evaluation Clear Error Highlight Removes the red background that signals the source location of an error Create Executable Creates a separate launcher for running your program See sec executables for more info Create Servlet Creates a servlet with the contents of the current definitions window for use in the web server Module Browser Prompts for a file and then opens a window showing the module import structure for the module import DAG starting at the selected module The module browser window contains a square for eac
34. irectory as the preferences file Under Windows and Mac OS Classic the lock file is named LOCKplt prefs ss and on other platforms it is LOCK plt prefs ss 1The MzScheme procedure find system path returns the platform specific path when given the argument pref file 22 3 Interface Reference 3 4 DrScheme Files If the user specific preferences file does not exist and the file plt prefs ss in the defaults collection does exist then it is used for the initial preference settings See Library Collections and MzLib 16 in PLT MzScheme Language Manual for more information about collections This file thus allows site specific configuration for preference defaults To set up such a configuration start DrScheme and configure the preferences to your liking Then exit DrScheme and copy your preferences file into the defaults collection as plt prefs ss Afterward users have no preferences will get the preference settings you chose 23 4 Extending DrScheme DrScheme supports two forms of extension to the programming environment e A teachpack extends the set of procedures that are built into a language in DrScheme For example a teachpack might extend the Beginning Student language with a procedure for playing sounds Teachpacks are particularly useful in a classroom setting where an instructor can provide a teachpack that is designed for a specific exercise To use the teachpack each student must download the teachpack file an
35. le search The results of the search are displayed in a separate window Close Closes this DrScheme window If this window is the only open DrScheme window DrScheme quits Quit or Exit Exits DrScheme under Mac OS X this menu item is in the apple menu 13 3 1 Menus 3 Interface Reference 3 1 2 Edit All Edit menu items operate on either the definitions or interactions window depending on the location of the selection or blinking caret Each window maintains its own Undo and Redo history Undo Reverses an editing action Each window maintains a history of actions so multiple Undo operations can reverse multiple editing actions Redo Reverses an Undo action Each window and boxed subwindow maintains its own history of Undo actions so multiple Redo operations can reverse multiple Undo actions Cut Copies the selected text to the clipboard and deletes it from the window Copy Copies the selected text to the clipboard Paste Pastes the current clipboard contents into the window Delete or Clear Deletes the selected text Select All Highlights the entire text of the buffer Wrap Text Toggles between wrapped text and unwrapped text in the window Find Opens a search dialog or depending on the preferences an interactive searching window attached to the frame Find Again Finds the next occurrence of the text that was last searched for Replace amp Find Again Replaces the selection with the replace string if it matches t
36. lent and x and X represent the same value The teaching languages are case sensitive by default and other languages are usually case insensitive Case sensitivity can be adjusted through the detail section of the language selection dialog More precisely Pretty Big is MrEd extended with the following MzLib libraries see PLT MzLib Libraries Manual etc ss file ss list ss class ss unit ss unitsig ss include ss defmacro ss pretty ss string ss thread ss math ss match ss and shared ss 2 5 Languages 2 Interface Essentials e All numbers are exact unless i is specified In the Beginning Student through Intermediate Student with Lambda languages numbers containing a decimal point are interpreted as exact numbers This interpretation allows students to use familar decimal notation without inadvertently triggering inexact arithmetic Exact numbers with decimal representations are also printed in decimal Inexact inputs and results are explicitly marked with i e Procedures must take at least one argument In the Beginning Student through Intermediate Student languages defined procedures must consume at least one argument Since the languages have no side effects zero argument functions are not useful and rejecting such function definitions helps detect confusing syntactic mistakes e Identifier required at function call position In the Beginning Student through Intermediate Student languages procedure calls must
37. levels See the Professor Beginner Language ProfessorJ Intermediate Language and Professor Advanced Language manuals for details Insert XML Box This menu item inserts an XML box XML boxes must contain XML s concrete syntax and they evaluate to x expressions which are s expressions representing the XML expression See also drscheme sec xml Insert Scheme Box Inserts a Scheme box These boxes contain Scheme code and are meant to be inside XML boxes See also drscheme sec xml Insert Scheme Splice Box Inserts a Scheme splice box These boxes are intended to be inside XML boxes The Scheme ex pression inside must evaluate to a list and that list is spliced into the containing XML box See also drscheme sec xml Insert Test Case Creates a new test case box see section 2 10 3 Interface Reference 3 2 Preferences 3 1 7 Windows e Bring Frame to Front Opens a window that lists all of the opened DrScheme frames Selecting one of them brings the window to the front e Most Recent Window Toggles between the currently focused window and the one that most recently had the focus Additionally after the above menu items this menu contains an entry for each window in DrScheme Se lecting a menu item brings the corresponding window to the front 3 1 8 Help e Help Desk Opens the Help Desk This is the clearing house for all documentation about DrScheme and its language e About DrScheme Shows the credits for DrScheme e
38. llowed In the Beginning Student through Advanced Student languages every variable referenced in the definitions window must be defined pre defined or the name of a local function argument e quote works only on symbols quasiquote diallowed In the Beginning Student language quote and can specify only symbols This restriction avoids the need to explain to beginners why 1 and 1 are equivalent in standard Scheme In addition quasiquote unquote unquote splicing and are disallowed e Unmatched cond case is an error In the Beginning Student through Advanced Student languages falling through a cond or case expression without matching a clause signals a run time error This convention helps detect syntactic and logical errors in programs e Conditional values must be true or false In the Beginning Student through Advanced Student languages an expression whose value is treated as a boolean must return an actual boolean true or false This restriction which applies to if cond and or nand and nor expressions helps detect errors where a boolean function application is omitted e and take at least two arguments In the Beginning Student through Advanced Student languages mathematical operators that are infix in algebra notation require at least two arguments in DrScheme This restriction helps detect missing arguments to an operator e and or nand and nor require at least 2 expressions In the
39. load links as well as the file size at the top of the page How much disk space does DrScheme consume Around 35 MB in its normal configuration not including the optional documentation 5 2 Using DrScheme How do I find general help for DrScheme Select Help Desk in DrScheme s Help menu How can I get my browser to find Help Desk when it s configured to use a Web proxy Help Desk uses a Web server running on the machine running DrScheme A Web proxy does not know about that server In your browser options have the browser ignore the proxy for the address 127 0 0 1 How do I run MrFlow DrScheme s program analyzer and the successor to MrSpidey MrFlow is distributed separately from the standard DrScheme distribution Download MrFlow from http www plt scheme org software mrflow What happened to the Analyze button Starting with version 51 PLT distributes DrScheme without the analysis tool See the previous answer for information about obtaining MrFlow 28 5 Frequently Asked Questions 5 2 Using DrScheme How do I customize DrScheme The Edit menu contains a Preferences item that opens the preferences dialog How do I turn off parenthesis flashing and the gray background behind expressions Use the Edit Preferences menu item What are the key bindings in DrScheme Some basic key bindings are listed in the DrScheme manual which is accessible via the Help button in DrScheme See also the Keybindings menu it
40. lso ask you to choose a base executable The choices are MrEd and MzScheme MzScheme exectables are smaller but have no graphical libraries Also under Mac OS X executables created with MzScheme as the base can only be run from the commandline Using the MrEd base executable means that your executable can also be launched from the finder Tip Disable debugging in the language dialog before creating your launcher With debugging enabled you will see a stack trace with error messages but your program will run more slowly To disable debugging open the language dialog click the Show Details button and click the No debugging or profiling check box if it is available 2 Interface Essentials 2 7 Printed Results Input Expression Constructor output write output cons 1 2 cons 1 2 G 2 list 1 2 list 1 2 1 2 2002 list 1 2 1 2 vector 1 2 3 vector 1 2 3 1 2 3 box 1 box 1 81 lambda x x lambda a lt procedure gt gt sym gt sym sym make s 1 2 make s 1 2 lt structure s gt 20 empty O t true t f false f addi addi lt primitive add1 gt list void list void lt void gt make weak box 1 make weak box 1 lt weak box gt delay 1 delay lt promise gt regexp a regexp lt regexp gt Figure 2 1 Comparison of constructor style output to write 2 7 Printed Results This section describ
41. nition of square as in the figure above typing square 2 in the interactions window produces the result 4 The status line at the bottom of DrScheme s window provides information about the current line and position of the editing caret whether the current file can be modified and whether DrScheme is currently evaluating any expression The recycling icon flashes while DrScheme is recycling internal resources such as memory 2 1 Buttons The left end of the row of buttons in DrScheme contains a miniature button with the current file s name Clicking the button opens a menu that shows the file s full pathname Selecting one of the menu entries opens file starting in the corresponding directory 2 Interface Essentials 2 2 The Editor Below the filename button is a define button for a popup menu of names defined in the definitions window Selecting an item from the menu moves the blinking caret to the corresponding definition The Save button appears whenever the definitions window is modified Clicking the button saves the contents of the definitions window to a file The current name of the file appears to the left of the Save button but a file selection dialog appears if the file has never been saved before The Step button starts The Stepper which shows the evaluation of a program as a series of small steps Each evaluation step replaces an expression in the program with an equivalent one using the evaluation rules of
42. nly the tools in those collections are loaded The contents of the environment variable are read and expected to be a single symbol or a list of symbols PLTDRCM When this environment variable is set DrScheme installs the compilation manager before starting up which means that the zo files are automatically kept up to date as DrScheme s or a tools source is modified If the variable is set to trace then CM s output is traced using the manager trace handler procedure from the CM library PLTHDCM When this environment variable is set Help Desk installs the compilation manager before starting up but only in standalone mode which means that the zo files are automatically kept up to date as Help Desk s source is modified If the variable is set to trace then CM s output is traced using the manager trace handler procedure from the CM library 25 4 8 Environment Variables 4 Extending DrScheme e PLTDRDEBUG When this environment variable is set DrScheme starts up with errortrace enabled If the variable is set to profile DrScheme also records profiling information about itself e PLTDRTESTS When this environment variable is set DrScheme installs a special button in the button bar that starts the test suite This is only available in the source distribution e PLTSTRINGCONSTANTS When this environment variable is set DrScheme prints out the string constants that have not yet been translated If it is set to a particular langu
43. nsert Comment Box Inserts a box that is ignored by DrScheme use it to put comments to people reading your program Insert Image Opens a find file dialog for selecting an image file in GIF BMP XBM or XPM format The image is treated as a value Insert Fraction OPENS a dialog prompting for a mixed notation fraction and inserts that into the current editor Insert Large Letters Opens a dialog asking for a line of text and inserts a large version of that made with semicolons and spaces into the current editor Insert Lambda Inserts the symbol A into the program This has the same behavior as if lambda were typed at this point except that the A symbol is implicitly delimited from neighboring characters Insert Delta define Inserts the symbol 6 into the program This has the same behavior as if define were typed at this point except that the 4 symbol is implicitly delimited from neighboring characters Insert Java Comment Box Inserts a box that is ignored by DrScheme unlike the Insert Comment Box menu item this is designed for the ProfessorJ language levels See the ProfessorJ Beginner Language ProfessorJ Intermediate Language and Professor Advanced Language manuals for details Insert Java Interactions Box Inserts a box that will act like an interactions window for Java This box will accept one Java statement or expression per line and should only appear at the top level This is intended for use in the ProfessorJ language
44. op the first is a comment that names the test case The second is an expression to test The third is the expected result Below the execpted result is a light blue box that will contain the actual result of the expression to be tested Clicking on the triangle in the top right hides the expression to test and the expected and actual results To run the test cases simply click execute The top right corner of the test case will change to either be a check box or a red X indicating success or failure of the test case 11 2 10 Test Cases 2 Interface Essentials To disable all of the test cases in the definitions window choose the Disable All Test Cases menu item in the Scheme menu 12 3 3 1 Interface Reference Menus 3 1 1 File New Creates a new DrScheme window Open Opens a find file dialog for choosing a file to load into a definitions window Open Recent Lists recently opened files Choosing one of them opens that file for editing Install PLT File Opens a dialog asking for the location of the PLT file either on the local disk or on the web and installs the contents of the PLT file Revert Re loads the file that is currently in the definitions window All changes since the file was last saved will be lost Save Definitions Saves the program in the definitions window If the program has never been saved before a save file dialog appears Save Definitions As Opens a save file dialog for choosing a de
45. or right button clicking depending on the platform DrScheme runs on on the argument to require activates a popup menu that lets you open the file that contains the required module Passing the mouse cursor over a require expression inside a module shows all of the variables that are used from that require expression Additionally if no variables are used from that require expression it is colored like an unbound variable Also passing the mouse cursor over a variable that is imported from a module shows the module that it is imported from in a status line at the bottom of the frame The Execute button evaluates the program in the definitions window and resets the interactions window The Break button interrupts an evaluation or beeps if DrScheme is not evaluating anything For example after clicking Execute or entering an expression into the interactions window click Break to cancel the evaluation Click the Break button once to try to interrupt the evaluation gracefully click the button twice to killing the evaluation immediately 2 2 The Editor DrScheme s editor provides special support for managing parentheses in a program When the blinking caret is next to a parenthesis DrScheme shades the region between the parenthesis and its matching parenthesis 2 3 The Interactions Window 2 Interface Essentials This feature is especially helpful when for balancing parentheses to complete an expression Furthermore if you type a clo
46. ox as input If you execute the program define v read display v v and provide the input S expression 1 2 the interactions window ultimately appears as follows 1 2 1 2 cons 1 cons 2 empty gt In this example display produces output immediately beneath the input you typed but the final result was printed outside the box because it is the result of the program rather than explicit output The above 10 2 Interface Essentials 2 9 XML example assumes constructor style printing With traditional value printing the final line outside the box would be 1 2 Entering the same program line by line in the interactions window produces a different looking result gt define v read 1 2 gt display v 1 2 gt v cons 1 cons 2 empty gt Although it is the same program as before entering the program expression by expression demonstrates how each prompt creates its own I O box 2 9 XML DrScheme has special support for XML concrete syntax The Special menu s Insert XML Box menu inserts an embedded editor into your program In that embedded editor you type XML s concrete syntax When a program containing an XML box is evaluated the XML box is translated into an x expression or xexpr Xexprs are s expression representation for XML expressions Each xexpr is a list whose first element is a symbol naming the tag second element is an association list repres
47. plete sexpression e M wrap selection in parentheses 20 3 Interface Reference 3 4 DrScheme Files e M wrap selection in square brackets e M wrap selection in curly brackets e M S L wrap selection in lambda and put the insertion point in the arglist of the lambda e C _ undo e C redo e C x u undo e M o toggle overwrite mode 3 3 3 File Operations e C x C s save file e C x C w save file under new name 3 3 4 Searching e C s search for string forward e C r search for string backward 3 3 5 Miscellaneous e f5 Execute 3 3 6 Interactions The interactions window has all of the same keyboard shortcuts as the definitions window plus a few more e M p bring the previously executed expression down to the prompt e M n bring the expression after the current expression in the expression history down to the prompt 3 4 DrScheme Files 3 4 1 Program Files The standard extension for a Scheme program file is scm The extensions ss and sch are also acceptable DrScheme s editor can saves a program file in two different formats e Plain text format All text editors can read this format DrScheme saves a program in plain text format by default unless the program contains images or text boxes Plain text format does not preserve images or text boxes Plain text format is platform specific because different platforms have different newline conventions However most tools for moving files acros
48. r teachpack is changed without a corresponding click on Execute Otherwise the warning appears on every interaction Ask about clearing test coverage If checked when test coverage annotations are displayed DrScheme prompts about removing them This setting only applies to the PLT languages DrScheme never asks in the teaching languages This preference panel configures the profiling report The band of color shows the range of colors that profiled functions take on Colors near the right are used for code that is not invoked often and colors on the right are used for code that is invoked often If you are interested in more detail at the low end choose the Square root check box If you are interested in more detail at the upper end choose the Square check box 3 Interface Reference 3 3 Keyboard Shortcuts e Browser The Use Help Desk browser for external URLs check box determines if Help Desk visits urls that lead out of our documentation in the platform specific browser or with Help Desk itself This preferences panel also allows you to configure your HTTP proxy Contact your system adminis trator for details 3 3 Keyboard Shortcuts Most key presses simply insert a character into the editor a 3 etc Other keys and key combina tions act as keyboard shortcuts that move the blinking caret delete a line copy the selection etc Keyboard shortcuts are usually trigger by key combinations using
49. re allowed only in the definitions window In the Beginning Student languages function definitions are not allowed in the interactions window The teaching languages also deviate from traditional Scheme in printing values Different printing formats can be selected for any language through the detail section of language selection dialog e Constructor style output See drscheme sec printing cons e Quasiquote style output See drscheme sec printing quasi e Rational number printing In the teaching languages all numbers that have a finite decimal expansion are printed in decimal form For those numbers that do not have a finite decimal expansion such as 4 3 DrScheme gives you a choice It either prints them as mixed fractions or as repeating decimals where the repeating portion of the decimal expansion is shown with an overbar In addition DrScheme only shows the first 25 digits of the number s decimal expansion If there are more digits the number appears with an ellipses at the end Click the ellipses to see the next 25 digits of the expansion This setting only controls the initial display of a number Right clicking or control clicking on the number lets you change from the fraction representation to the decimal representation e write output Prints values with write e Show sharing in values Prints interaction results using the shared syntax which exposes shared structure within a value For example the list create
50. rtable editing in Emacs and find the standard menu keybindings interfere with the Emacs keybindings x Color syntax interactively If checked DrScheme colors your syntax as you type Automatically print to postscript file If checked printing will automatically save postscript files If not printing will use the standard printing mechanisms for your computer Scheme e Warnings x e Profiling Highlight between matching parens If checked the editor marks the region between matching parenthesis with a gray background in color or a stipple pattern in monochrome when the flashing caret is next to a parenthesis Correct parens If checked the editor automatically converts a typed to to match or it converts a typed to to match Flash paren match If checked typing a closing parenthesis square bracket or quotation mark flashes the matching open parenthesis bracket quote Parenthesis highlight color configures the color used to highlight matching parenthesis Ask before changing save format If checked DrScheme consults the user before saving a file in non text format see drscheme file formats Verify exit If checked DrScheme consults the user before exiting Only warn once when executions and interactions are not synchronized If checked DrScheme warns the user on the first interaction after the definitions window language o
51. s not provide DrScheme s various languages and error messages in MrEd do not provide a source code location MzScheme is PLT s Scheme implementation The language is the same as MrEd without graphics MzScheme provides little programming support so its memory requirements are minimal a few MB usually suffices The standard DrScheme distribution includes all of the above programs MzScheme distributions can be downloaded through http www plt scheme org software mzscheme 27 5 2 Using DrScheme 5 Frequently Asked Questions Does DrScheme run under Mac OS versions earlier than Mac OS X No Does DrScheme run under DOS or Windows 3 1 No Does MzScheme PLT s text only Scheme run under DOS or Windows 3 1 No How do I install DrScheme Obtain a DrScheme distribution from the above address For Windows the distribution is an installer program running this program installs DrScheme For MacOS the distributiton is a disk image containing a meta package mpkg installer For Unix X the distribution is a self extracting shell program running it will unpack and install the archive and can help in setting up some standard links In all cases the final download page provides detailed platform specific installation instructions How large is the distribution archive Distribution archives vary in sizes From the download page select your platform and click the download button the next screen will have down
52. s platforms support a text transfer mode that adjusts newlines correctly 21 3 4 DrScheme Files 3 Interface Reference e Multimedia format This format is specific to DrScheme and no other editor recognizes it DrScheme saves a program in multimedia format by default when the program contains images text boxes or formatted text Multimedia format is platform independent Use a binary transfer mode when moving multimedia format files across platforms Using text mode may corrupt the file 3 4 2 Backup and Autosave Files When you modify an existing file in DrScheme and save it DrScheme copies the old version of the file to a special backup file if no backup file exists The backup file is saved in the same directory as the original file and the backup file s name is generated from the original file s name e Under Unix and Mac OS a tilde is added to the end of the file s name e Under Windows the file s extension is replaced with bak When a file in an active DrScheme editor is modified but not saved DrScheme saves the file to a special autosave file after five minutes in case of a power failure or catastrophic error If the file is later saved or if the user exists DrScheme without saving the file the autosave file is removed The autosave file is saved in the same directory as the original file and the autosave file s name is generated from the original file s name e Under Unix
53. sing parenthesis that should match an opening square bracket the editor automatically converts the into a J DrScheme beeps whenever a closing parenthesis does not match an opening parenthesis Although whitespace is not significant in Scheme DrScheme encourages a particular format for Scheme code When you type Enter or Return the editor inserts a new line and automatically indents it To make DrScheme re indent an existing line move the flashing caret to the line and hit the Tab key The caret can be anywhere in the line You can re indent an entire region by selecting the region and typing Tab 2 3 The Interactions Window The interactions window lets you type an expression after the gt prompt for immediate evaluation You cannot modify any text before the last gt prompt To enter an expression the flashing caret must appear after the last prompt and also after the space following the prompt When you type a complete expression and hit Enter or Return DrScheme evaluates the expression and prints the result After printing the result DrScheme creates a new prompt for another expression Some expressions return a special void value DrScheme never prints void but instead produces a new prompt immediately If the expression following the current prompt is incomplete then DrScheme will not try to evaluate it In that case hitting Enter or Return produces a new auto indented line You can force DrSch
54. stination file to save the program in the definitions window Subsequent saves write to the newly selected file Save Other Contains these sub items Save Definitions As Text Like Save Definitions As but the file is saved in plain text format see drscheme file formats Subsequent saves also write in plain text format Save Interactions Saves the contents of the interactions window to a file If the interaction constants have never been saved before a save file dialog appears Save Interactions As Opens a save file dialog for choosing a destination file to save the contents of the interactions window Subsequent saves write to the newly selected file Save Interactions As Text Like Save Interactions As but the file is saved in plain text format see drscheme file formats Subsequent saves are write in plain text format Log Definitions and Interactions Starts a running of log of the text in the interactions and definitions windows organized by executions In a directory of your choosing DrScheme saves files with the names 01 definitions 01 interactions 02 definitions 02 interactions etc as you execute and interact with various programs Print Definitions Opens a dialog for printing the current program in the definitions window Print Interactions Opens a dialog for printing the contents of the interactions window Search in Files Opens a dialog where you can specify the parameters of a multi fi
55. turn to copy the expression down to the current prompt Why doesn t let work or letrec or lambda or set etc DrScheme is initially configured to use the Beginning Student teaching language This language prevents many common student errors but will not evaluate all Scheme programs To remedy this choose a language such as Standard or Pretty Big Is there a DrScheme compiler Technically DrScheme is a compiler as well as an interpreter Each time the user loads a program or enters expression in the interactions window DrScheme compiles and then executes the program or expression PLT s mzc transforms Scheme programs into C programs and then uses a third party C compiler to produce executable code Under Windows either Microsoft Visual C or gcc a free compiler from Cygnus Solutions works as the C compiler Under MacOS CodeWarrior works Under Unix most any compiler works For details see the mzc documentation available from http download plt scheme org doc 29 5 3 Memory and Performance 5 Frequently Asked Questions Can I produce stand alone executables from Scheme code To produce a standalone executable that only works for your particular installation of DrScheme see sec executables In addition the mzc compiler can be used to produce stand alone executables See the mzc documentation for more information Can files saved in DrScheme be transferred between platforms DrScheme saves
Download Pdf Manuals
Related Search