RLisp: User Manual
Contents
1. e If name is a pair and object evaluated is also a pair then def is transformed in two defs and so on recursively def car name car object def cdr name cdr object e Lastly if name is a pair but object evaluated is not a pair then no assignment takes place The primitive to change a name meaning is set and works with respect to pairs the same way as def works The name should be already defined otherwise set do nothing set name object If you omit object set name then name gets undefined 22 5 Atom Evaluation If a name was already defined and it was not undefined then it evaluates to its definition If a name is a primitive name then it evaluates conforming to the primitive meaning Any other name is the name of itself that is it evaluates to the String literal that is itself three evaluates to the five characters String three and 12 to the String 12 so in our Lisp all atoms are evaluable 22 6 The Syntactic Primitives Lisp RLisp is minimalist and it only employs the following syntactic primitives quote is as in Scheme and the single quote is also its abbreviation eval is as in Scheme def and set are as explained above cond and eq where cond is as in Scheme except that there is not else but you can use t instead and where eq is as equal in Scheme e cons car and cdr are as in Scheme but cons evaluates to nil and cons 1 to 1 e atom is as2. 5 Starting To start RLisp you will have to call the Java virtual machine and instruct it to run the code in file RLisp jar That s all In Windows the command is java exe jar RLisp jar www ramoncasares com 20101127 RLispManE 2 6 The Main Window The Yellow Window If everything goes right then the RLisp main window also known as the yellow window will be open There are three parts in the main window that are from top down a toolbar that we will explain in the next sections a big yellow text area where every action and reaction will be noted that we will explain in this section and a status line where RLisp will show some additional information In the big yellow text area every command to and every result from RLisp will be written one in each line Command lines will begin with the pair of characters lt lt and lines showing the results will begin with gt gt For example lt lt new RLisp RPair string 1 2 3 gt 123 The first line in the example shows that we have asked RLisp to build a new object of class RLisp RPair using the constructor RPair String and as argument the String 1 2 3 including parentheses The second line is the answer from RLisp showing the new object You can give the new object a name to add it to the object dictionary so it will be available later on We will see that there are several ways to do this but in any case if we choose list123 as its name this act
3. be named pressing the Name button in the tree window or executing Action Name from the toolbar or as we will explain in the next section writting the command def name in the keyboard where is the RLisp way to refer to the last resulting object and name is the name we want give it www ramoncasares com 20101127 RLispManE 6 10 The Keyboard The Green Window When you execute File Keyboard RLisp opens a green window to enter text This way you can ask RLisp to execute any command from the keyboard These commands use the lispian syntax In the section titled Lisp we will explain in detail what commands do obey RLisp The green window keeps the record of the written parentheses so when all of them are closed i e paired and you type the end of line return key then it sends the whole expression to the main console where it is interpreted You can also ask the execution of an expression from the keyboard using its toolbar buttons They refer to the cursor current location For example when pressing the Maximum button the longest expression surrounding the cursor location is executed If you press the Minimum button then it takes the shortest expression to execute The Word button selects only the word in which the cursor currently is so in general RLisp only task will be to look up the word definition in the dictionary The Previous and Next buttons refer to the previous and to the following expression The only button
4. its class void does not appear in the signature of any constructor nor any method For this reason we should cast the value of null using the cons Class car nil variant Note that Java null cannot be included in the dictionary so you should use a Lisp expression as car nil to get the null 22 10 Other Initial Definitions In file RLispJava lisp which is called by RLisp 1lisp eight functions to get values of the eight basic types of Java are defined You can use them like this boolean false char c byte 5 short 233 int 12 long 1234567 float 1 4 double 4 234567e4 In file RLispMaths lisp also called by RLisp lisp the basic arithmetics func tions are defined addition substraction multiplication quotient and remainder and two conditions equal to and greater than gt It employs java math BigInteger numbers and expression 4 evaluates to the BigInteger number 4 If you need another type of arithmetics you should redefine this file In file RLispArray lisp also called by RLisp lisp the following functions to work with Java arrays are defined isArray o array length a array get a i array set a i v where o is any Object a an Array i an int used as index and v for the new value an Object To create an array you can use the semantic primitives array cl ob0 ob1 which creates a unidimensional array of length two initialized or new cl dimi dim2 which
5. ob mt argO argi where arg is ob or cons Class ob evaluates to the result of executing the method mt of object ob or of class cl which then should be static using as arguments arg0 arg1 etc please see further details below field cl ob wal evaluates to the current value of field f of object ob or of class cl If the optional val is present then the new value of the field f is val array cl ob0 ob1 evaluates to a new array of class cl objects initialized with objects ob0 ob1 etc path URL already seen load URL already seen In primitives that use a list of arguments which are new and method you will need to indicate the class of an argument using variant cons Class ob when you want to cast the object ob to a superclass of its proper class This happens for example when using a constructor or a method with an argument of class java lang Object as equals java lang Object because in spite that every www ramoncasares com 20101127 RLispManE 11 Java object belongs to some subclass of that class none of them belongs to it So assuming that both object1 and object2 belongs to a class that only defines equals that way then to call the method we should write method object1 equals cons java lang Object object2 Something similar happens when we need to use the value null While null can be the value of any class it does not properly belong to any class and therefore
6. such as Unix emacs or Windows notepad If you use instead a word processor for example MS Word then you will have to save it as text that is without any control code But the easiest way to create a log file is to let RLisp to do it If you stroke File Save to that is if you choose the option Save to after having selected File in the toolbar then RLisp starts an explorer to select a file name and a location in your computer to be used as a log file From this point in time on every piece of information shown in the main window will be also written to the selected log file The default log file is file RLisp log in the current directory This means that if you execute File Save then RLisp assumes that the log file is RLisp 1log in the current directory and it does not requires any other data The information saved to a log file can also be read If you execute File Load from then RLisp starts an explorer to choose a file By default only directories and files with the log extension are shown but you can instruct RLisp to show all files If you want to read the file RLisp log in the current directory then you should execute File Load In any case once the file is selected RLisp starts processing the log file Log file processing is easy If the three first characters of a line are not lt lt the third one is a space then RLisp just writes the line to the main window If contrarywise the first three characters of a
7. ariant we have chosen to develope the RLisp Lisp So we will explain the differences between our Lisp and Scheme Scheme being a well known Lisp dialect will not be explained here 22 2 Tail recursivity The main conceptual difference is that while Scheme is tail recursive our Lisp is not And this is so because Java or more preciselly the Java compiler is not tail recursive If some tail recursive Java compiler were developed then we should revise the RLisp code in order to conform it to the compiler requirements 22 3 Improper Lists Improper lists or pairs that are noted with a dot in Scheme are noted with 699 a comma in our Lisp The reason behind this difference is that in Java we use the www ramoncasares com 20101127 RLispManE 9 dot to refer to objects and this is a very frequent operation in RLisp For example to refer to a class method we have to write the class name a dot and the method name In addition the comma is used in Mathematics to express pairs car cdr so it is the most natural replacement for the dot 22 4 Pair Assignment Our Lisp assigner is very powerful The primitive operation to give an object a name in our Lisp is def def name object where name is not evaluated object is evaluated and then e If name is not a pair that is if atom name is t for true then the name name is added to the current dictionary with object evaluated as we have said as its meaning
8. creates a bidimensional array sized dim1 x dim2 not initialized that is initialized to null values
9. elp Spanish Manual command If RLisp is run in a Windows environment and both files RLispManE pdf or RLispManS pdf and RLisp jar are in the same directory then the predetermined action is executed on the pdf file The usual predetermined action on a pdf file is to open it with the Adobe s Acrobat Reader 20 The Source Code To know the name of a document where you can read the source code of RLisp you can execute the Help Code command If RLisp is run in a Windows environment and both files RLispCode pdf and RLisp jar are in the same directory then the predetermined action is executed on the pdf file The usual predetermined action on a pdf file is to open it with the Adobe s Acrobat Reader 21 About RLisp The command Help About RLisp shows you the version of RLisp that you are run ning the copyright and the name of its author that is my name If you don t like RLisp you can write me if you don t dislike it you can also write me 22 Lisp In this section we will explain the main characteristics of our Lisp Note that you can use RLisp without writting a single line in Lisp just inside the tree window you can create Java objects you can give the crated objects names you can execute the created objects methods and you can see the results So in this working mode Lisp is just a syntax to note the session events But using Lisp the possibilities of RLisp are enhanced enormously 22 1 Scheme Scheme is the Lisp v
10. in Scheme e lambda is as in Scheme but it employs when asigning formals to actuals all of the assigner power www ramoncasares com 20101127 RLispManE 10 rho is the way to create new special forms to extend the syntax We will explain it in the next section 22 7 The extensions To create new special forms and syntaxes in our Lisp we will employ rho To evaluate the rho expression rho name expander expression RLisp evaluates first expander name expression And then it evaluates the result 22 8 Initial Definitions When RLisp starts it loads the file RLisp lisp which is located inside the file RLisp jar In this file other known Lisp names are defined nil t nul1 not list cadr macro syntax define if sequence or and mapcar let GENV Gdefine You can browse this file to see some examples of rho usage though hidden behind syntax An easy way to extend RLisp is to add definitions to this file or to the files called by this one which are also inside RLisp jar We will see these files below 22 9 The Semantic Primitives Java Our Lisp can access Java objects In order to do this it provides the following seven semantic primitives string that is all evaluates to the Java String that is all new cl argO argi where arg is ob or cons Class ob evaluates to a new Java object of class cl using as arguments argO arg1 etc please see further details below method cl
11. ion will be set down in the main window as shown lt lt def list123 gt gt list123 If we now want for example to know the class of the named object then the note would be lt lt method list123 getClass gt gt class RLisp RPair www ramoncasares com 20101127 RLispManE 3 7 The Toolbar The toolbar has four sections e File to open data sources and sinks as the log files the tree and the keyboard e Edit to cut copy and paste e Action to execute Java access operations path or operations to read and execute Lisp code files Lisp code or operations related with the object dictionary name unname list e Help to access the documents The toolbar whole structure is as follows Load Load from Save Save to File Tree Keyboard Session Close Cut Tool bar Edit Copy Paste Path Lisp code Action Name Unname List Manual User Manual Spanish Manual Spanish Version Code RLisp Source Code About RLisp Help www ramoncasares com 20101127 RLispManE 4 8 The Log Files The log is a book in which the record of a ship s speed its progress and any shipboard events of navigation is kept To record the events happening when using RLisp we employ the log files For convenience log files should have a log extension though the code does not requires it nor verifies it but only makes using it easy RLisp logs are text files This means that they can be created with any text editor
12. line are in fact lt lt then RLisp writes the whole line in the main window and in addition it executes the rest of the line and writes the result in the main window The result is written in a single line in which the three first characters are gt lt and then goes the result The information written in the main window while processing a log file is not written to any log file and this is the only exception to the rule When you call RLisp you can append the name of a log file to be processed at start By default none is processed java exe jar RLisp jar filename log www ramoncasares com 20101127 RLispManE 5 9 The Tree The White Window If you execute File Tree then RLisp starts an explorer to choose a directory or a jar Java archive file When you select one RLisp opens a window with the tree of all classes files with the class extension that are accesible from it Please be aware that you should follow the Java access rules so if a class is defined in a package then the class is not accessible from the directory in where the class is located but from one which is up in the hierarchy For example if class MyClass is defined in package MyApplication then the file MyClass class should be in a subdirectory named MyApplication of a certain directory and it is from that certain directory from which the class MyClass is accessible For each class there are up to four branches e Array to create a unidimen
13. not asking to execute an expression is Nesting This button is used to ask RLisp to calculate the cursor position nesting level which is shown in the keyboard status bar located in the lower part of the green window 11 The Session If you execute the command File Session then RLisp will only accept commands written in the system console To return to the normal mode of operation you will have to write quit in the system console 12 To Close Executing File Close in the toolbar you close any open file managed by RLisp and finish RLisp Another way to quit RLisp is closing the main window And yet another one is to execute from the keyboard the command quit Lastly if processing a log file the following line is found lt lt quit then RLisp is also closed 13 To Edit In the Edit section of the toolbar you can find the usual commands to Cut Copy and Paste They are used to transfer information between aplications www ramoncasares com 20101127 RLispManE 7 14 The Path The Action Path command opens an explorer to select a directory Once selected the Java ClassLoader can access the classes that are accessible from the directory All of the warnings written in the Tree section concerning class accesibility apply again to this case To execute this action from Lisp where URL is the directory type path URL 15 Lisp Code When you execute Action Lisp code RLisp opens an explorer to select a file By default this e
14. sional array of objects of this class This branch is always present e Fields to access and modify if it is not final a field of the class e Constructors to create an object of the class e Methods to execute a method of the class Each of the four main branches except Array has a number of subbranches In branch Fields there is a subbranch for each and every accesible field of the class be it static or not be it declared in it or inherited from a superclass In branch Constructors there is a subbranch for each and every constructor in the class And in branch Methods there is one subbranch for each and every method of the class Once a subbranch is chosen you should press the OK button to execute the action associated to the subbranch Depending on the subbranch selected RLisp could ask you for additional data For example if you have chosen a non static method subbranch then RLisp will ask you to select an object between the named objects of the chosen class and a named object of the corresponding class for each of the arguments of the chosen method In each case instead of a named object you can enter a Lisp expression that RLisp will evaluate The executed command will be shown in the yellow main window la Lisp The command in one line that starts with lt lt and the result with the textual representation toString of the resulting Java object in the next line stating with gt gt The resulting object can
15. www ramoncasares com 20101127 RLispManE 1 RLisp User Manual 1 Introduction RLisp is a Java package to create Java objects and execute its methods in runtime It is then a Java interpreter But because this interpreter implements a whole Lisp machine we can also say that RLisp is a Lisp interpreter running on the Java semantics 2 License RLisp is open and free software under the GNU General Public License RLisp is copyright by Ramon Casares 3 The Files RLisp is distributed in four or three files RLisp jar is the program and the only one required RLispManE pdf is this document that you are reading RLispManS pdf is the Spanish version of this document RLispCode pdf is a document where you can find the whole source code in a human readable form and it is therefore RLisp conclusive specification O If you want to access the other three documents from the RLisp program in runtime then the four files should be located in the same directory If you want to hack RLisp you will find the source code files files with java extension inside the RLisp jar file 4 The Machine To run RLisp you will need a computer with a Java virtual machine JVM installed RLisp works with the JVM that is part of Sun s Java Runtime Environment JRE version 1 4 2 You can download the JRE from its official home in Internet It will surelly work with newer versions and possibly work with older versions but I am not sure
16. xplorer only shows the files with extension lisp though you can instruct it to show all of the files Once a file is selected RLisp executes each and every Lisp expression in the file You can execute this action in Lisp where URL is the file typing load URL 16 To Name If you want to give the current object a name you can use the Action Name command The current object is the object shown in the last line of the main window After naming an object we can refer to it by its name being this way accessible The Lisp equivalent to this action where is the way used in RLisp to refer to the last result and name is the name we want to give it is def name 17 To Unname If you want that a named and accessible object stops being so then you should use the Action Unname command You will be then presented a list with all the named objects to choose one of them The same action can be performed in Lisp where name is the unnamed name doing set name 18 To List The Action List command shows in the main window each and every named object with its Java class and its textual toString representation To get the class of an individual object you can use the Lisp command method object getClass www ramoncasares com 20101127 RLispManE 8 19 User Manual To know the name of this document you can execute the Help Manual command And to know the name of the Spanish version of this document you can execute the H
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