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XLISP: An Object-oriented Lisp Version 2.0 February 6, 1988 by David Michael Betz 127 Taylor Road Peterborough, NH 03458 (603) 924-6936 (home) Copyright (c) 1988, by David Michael Betz All Rights Reserved Permission is granted for unrestricted non-commercial use XLISP TABLE OF CONTENTS Page 2 Table of Contents TABLE OF CONTENTS 2 INTRODUCTION 4 A NOTE FROM THE AUTHOR 5 XLISP COMMAND LOOP 6 BREAK COMMAND LOOP 7 DATA TYPES 8 THE EVALUATOR 9 LEXICAL CONVENTIONS 10 READTABLES 11 LAMBDA LISTS 12 OBJECTS 14 SYMBOLS 17 EVALUATION FUNCTIONS 18 SYMBOL FUNCTIONS 19 PROPERTY LIST FUNCTIONS 21 ARRAY FUNCTIONS 22 LIST FUNCTIONS 23 DESTRUCTIVE LIST FUNCTIONS 26 PREDICATE FUNCTIONS 27 CONTROL CONSTRUCTS 29 LOOPING CONSTRUCTS 31 THE PROGRAM FEATURE 32 DEBUGGING AND ERROR HANDLING 33 ARITHMETIC FUNCTIONS 34 BITWISE LOGICAL FUNCTIONS 36 STRING FUNCTIONS 37 XLISP TABLE OF CONTENTS Page 3 CHARACTER FUNCTIONS 39 INPUT/OUTPUT FUNCTIONS 41 THE FORMAT FUNCTION 42 FILE I/O FUNCTIONS 43 STRING STREAM FUNCTIONS 44 SYSTEM FUNCTIONS 45 EXAMPLES 47 XLISP INTRODUCTION Page 4 INTRODUCTION XLISP is an experimental programming language combining some of the features of Common Lisp with an object-oriented extension capability. It was implemented to allow experimentation with object-oriented programming on small computers. There are currently implementations of XLISP running on the IBM- PC and clones under MS-DOS, on the Macintosh, the Atari-ST and the Amiga. It is completely written in the programming language 'C' and is easily extended with user written built-in functions and classes. It is available in source form to non-commercial users. Many Common Lisp functions are built into XLISP. In addition, XLISP defines the objects 'Object' and 'Class' as primitives. 'Object' is the only class that has no superclass and hence is the root of the class heirarchy tree. 'Class' is the class of which all classes are instances (it is the only object that is an instance of itself). This document is a brief description of XLISP. It assumes some knowledge of LISP and some understanding of the concepts of object-oriented programming. I recommend the book "LISP" by Winston and Horn and published by Addison Wesley for learning Lisp. The first edition of this book is based on MacLisp and the second edition is based on Common Lisp. XLISP will continue to migrate towards compatibility with Common Lisp. You will probably also need a copy of "Common Lisp: The Language" by Guy L. Steele, Jr., published by Digital Press to use as a reference for some of the Common Lisp functions that are described only briefly in this document. XLISP A NOTE FROM THE AUTHOR Page 5 A NOTE FROM THE AUTHOR If you have any problems with XLISP, feel free to contact me for help or advice. Please remember that since XLISP is available in source form in a high level language, many users have been making versions available on a variety of machines. If you call to report a problem with a specific version, I may not be able to help you if that version runs on a machine to which I don't have access. Please have the version number of the version that you are running readily accessible before calling me. If you find a bug in XLISP, first try to fix the bug yourself using the source code provided. If you are successful in fixing the bug, send the bug report along with the fix to me. If you don't have access to a C compiler or are unable to fix a bug, please send the bug report to me and I'll try to fix it. Any suggestions for improvements will be welcomed. Feel free to extend the language in whatever way suits your needs. However, PLEASE DO NOT RELEASE ENHANCED VERSIONS WITHOUT CHECKING WITH ME FIRST!! I would like to be the clearing house for new features added to XLISP. If you want to add features for your own personal use, go ahead. But, if you want to distribute your enhanced version, contact me first. Please remember that the goal of XLISP is to provide a language to learn and experiment with LISP and object-oriented programming on small computers. I don't want it to get so big that it requires megabytes of memory to run. XLISP XLISP COMMAND LOOP Page 6 XLISP COMMAND LOOP When XLISP is started, it first tries to load the workspace "xlisp.wks" from the current directory. If that file doesn't exist, XLISP builds an initial workspace, empty except for the built-in functions and symbols. Then XLISP attempts to load "init.lsp" from the current directory. It then loads any files named as parameters on the command line (after appending ".lsp" to their names). XLISP then issues the following prompt: > This indicates that XLISP is waiting for an expression to be typed. When a complete expression has been entered, XLISP attempts to evaluate that expression. If the expression evaluates successfully, XLISP prints the result and then returns to the initial prompt waiting for another expression to be typed. XLISP BREAK COMMAND LOOP Page 7 BREAK COMMAND LOOP When XLISP encounters an error while evaluating an expression, it attempts to handle the error in the following way: If the symbol '*breakenable*' is true, the message corresponding to the error is printed. If the error is correctable, the correction message is printed. If the symbol '*tracenable*' is true, a trace back is printed. The number of entries printed depends on the value of the symbol '*tracelimit*'. If this symbol is set to something other than a number, the entire trace back stack is printed. XLISP then enters a read/eval/print loop to allow the user to examine the state of the interpreter in the context of the error. This loop differs from the normal top-level read/eval/print loop in that if the user invokes the function 'continue', XLISP will continue from a correctable error. If the user invokes the function 'clean-up', XLISP will abort the break loop and return to the top level or the next lower numbered break loop. When in a break loop, XLISP prefixes the break level to the normal prompt. If the symbol '*breakenable*' is nil, XLISP looks for a surrounding errset function. If one is found, XLISP examines the value of the print flag. If this flag is true, the error message is printed. In any case, XLISP causes the errset function call to return nil. If there is no surrounding errset function, XLISP prints the error message and returns to the top level. XLISP DATA TYPES Page 8 DATA TYPES There are several different data types available to XLISP programmers. o lists o symbols o strings o integers o characters o floats o objects o arrays o streams o subrs (built-in functions) o fsubrs (special forms) o closures (user defined functions) XLISP THE EVALUATOR Page 9 THE EVALUATOR The process of evaluation in XLISP: Strings, integers, characters, floats, objects, arrays, streams, subrs, fsubrs and closures evaluate to themselves. Symbols act as variables and are evaluated by retrieving the value associated with their current binding. Lists are evaluated by examining the first element of the list and then taking one of the following actions: If it is a symbol, the functional binding of the symbol is retrieved. If it is a lambda expression, a closure is constructed for the function described by the lambda expression. If it is a subr, fsubr or closure, it stands for itself. Any other value is an error. Then, the value produced by the previous step is examined: If it is a subr or closure, the remaining list elements are evaluated and the subr or closure is called with these evaluated expressions as arguments. If it is an fsubr, the fsubr is called using the remaining list elements as arguments (unevaluated). If it is a macro, the macro is expanded using the remaining list elements as arguments (unevaluated). The macro expansion is then evaluated in place of the original macro call. XLISP LEXICAL CONVENTIONS Page 10 LEXICAL CONVENTIONS The following conventions must be followed when entering XLISP programs: Comments in XLISP code begin with a semi-colon character and continue to the end of the line. Symbol names in XLISP can consist of any sequence of non-blank printable characters except the following: ( ) ' ` , " ; Uppercase and lowercase characters are not distinguished within symbol names. All lowercase characters are mapped to uppercase on input. Integer literals consist of a sequence of digits optionally beginning with a '+' or '-'. The range of values an integer can represent is limited by the size of a C 'long' on the machine on which XLISP is running. Floating point literals consist of a sequence of digits optionally beginning with a '+' or '-' and including an embedded decimal point. The range of values a floating point number can represent is limited by the size of a C 'float' ('double' on machines with 32 bit addresses) on the machine on which XLISP is running. Literal strings are sequences of characters surrounded by double quotes. Within quoted strings the '\' character is used to allow non-printable characters to be included. The codes recognized are: \\ means the character '\' \n means newline \t means tab \r means return \f means form feed \nnn means the character whose octal code is nnn XLISP READTABLES Page 11 READTABLES The behaviour of the reader is controlled by a data structure called a "readtable". The reader uses the symbol *READTABLE* to locate the current readtable. This table controls the interpretation of input characters. It is an array with 128 entries, one for each of the ASCII character codes. Each entry contains one of the following things: NIL Indicating an invalid character :CONSTITUENT Indicating a symbol constituent :WHITE-SPACE Indicating a whitespace character (:TMACRO . fun) Terminating readmacro (:NMACRO . fun) Non-terminating readmacro :SESCAPE Single escape character ('\') :MESCAPE Multiple escape character ('|') In the case of :TMACRO and :NMACRO, the "fun" component is a function. This can either be a built-in readmacro function or a lambda expression. The function should take two parameters. The first is the input stream and the second is the character that caused the invocation of the readmacro. The readmacro function should return NIL to indicate that the character should be treated as white space or a value consed with NIL to indicate that the readmacro should be treated as an occurance of the specified value. Of course, the readmacro code is free to read additional characters from the input stream. XLISP defines several useful read macros: '<expr> == (quote <expr>) #'<expr> == (function <expr>) #(<expr>...) == an array of the specified expressions #x<hdigits> == a hexadecimal number (0-9,A-F) #o<odigits> == an octal number (0-7) #b<bdigits> == a binary number (0-1) #\<char> == the ASCII code of the character #| ... |# == a comment #:<symbol> == an uninterned symbol `<expr> == (backquote <expr>) ,<expr> == (comma <expr>) ,@<expr> == (comma-at <expr>) XLISP LAMBDA LISTS Page 12 LAMBDA LISTS There are several forms in XLISP that require that a "lambda list" be specified. A lambda list is a definition of the arguments accepted by a function. There are four different types of arguments. The lambda list starts with required arguments. Required arguments must be specified in every call to the function. The required arguments are followed by the &optional arguments. Optional arguments may be provided or omitted in a call. An initialization expression may be specified to provide a default value for an &optional argument if it is omitted from a call. If no initialization expression is specified, an omitted argument is initialized to NIL. It is also possible to provide the name of a 'supplied-p' variable that can be used to determine if a call provided a value for the argument or if the initialization expression was used. If specified, the supplied- p variable will be bound to T if a value was specified in the call and NIL if the default value was used. The &optional arguments are followed by the &rest argument. The &rest argument gets bound to the remainder of the argument list after the required and &optional arguments have been removed. The &rest argument is followed by the &key arguments. When a keyword argument is passed to a function, a pair of values appears in the argument list. The first expression in the pair should evaluate to a keyword symbol (a symbol that begins with a ':'). The value of the second expression is the value of the keyword argument. Like &optional arguments, &key arguments can have initialization expressions and supplied-p variables. In addition, it is possible to specify the keyword to be used in a function call. If no keyword is specified, the keyword obtained by adding a ':' to the beginning of the keyword argument symbol is used. In other words, if the keyword argument symbol is 'foo', the keyword will be ':foo'. The &key arguments are followed by the &aux variables. These are local variables that are bound during the evaluation of the function body. It is possible to have initialization expressions for the &aux variables. XLISP LAMBDA LISTS Page 13 Here is the complete syntax for lambda lists: (<rarg>... [&optional [<oarg> | (<oarg> [<init> [<svar>]])]...] [&rest <rarg>] [&key [<karg> | ([<karg> | (<key> <karg>)] [<init> [<svar>]])]... &allow-other-keys] [&aux [<aux> | (<aux> [<init>])]...]) where: <rarg> is a required argument symbol <oarg> is an &optional argument symbol <rarg> is the &rest argument symbol <karg> is a &key argument symbol <key> is a keyword symbol <aux> is an auxiliary variable symbol <init> is an initialization expression <svar> is a supplied-p variable symbol XLISP OBJECTS Page 14 OBJECTS Definitions: o selector - a symbol used to select an appropriate method o message - a selector and a list of actual arguments o method - the code that implements a message Since XLISP was created to provide a simple basis for experimenting with object-oriented programming, one of the primitive data types included is 'object'. In XLISP, an object consists of a data structure containing a pointer to the object's class as well as an array containing the values of the object's instance variables. Officially, there is no way to see inside an object (look at the values of its instance variables). The only way to communicate with an object is by sending it a message. You can send a message to an object using the 'send' function. This function takes the object as its first argument, the message selector as its second argument (which must be a symbol) and the message arguments as its remaining arguments. The 'send' function determines the class of the receiving object and attempts to find a method corresponding to the message selector in the set of messages defined for that class. If the message is not found in the object's class and the class has a super-class, the search continues by looking at the messages defined for the super-class. This process continues from one super-class to the next until a method for the message is found. If no method is found, an error occurs. A message can also be sent from the body of a method by using the current object, but the method lookup starts with the object's superclass rather than its class. This allows a subclass to invoke a standard method in its parent class even though it overrides that method with its own specialized version. When a method is found, the evaluator binds the receiving object to the symbol 'self' and evaluates the method using the remaining elements of the original list as arguments to the method. These arguments are always evaluated prior to being bound to their corresponding formal arguments. The result of evaluating the method becomes the result of the expression. XLISP OBJECTS Page 15 THE 'Object' CLASS Classes: Object THE TOP OF THE CLASS HEIRARCHY Messages: :show SHOW AN OBJECT'S INSTANCE VARIABLES returns the object :class RETURN THE CLASS OF AN OBJECT returns the class of the object :isnew THE DEFAULT OBJECT INITIALIZATION ROUTINE returns the object :sendsuper <sel> <args>... SEND SUPERCLASS A MESSAGE <sel> the message selector <args> the message arguments returns the result of sending the message XLISP OBJECTS Page 16 THE 'Class' CLASS Class THE CLASS OF ALL OBJECT CLASSES (including itself) Messages: :new CREATE A NEW INSTANCE OF A CLASS returns the new class object :isnew <ivars> [<cvars> [<super>]] INITIALIZE A NEW CLASS <ivars> the list of instance variable symbols <cvars> the list of class variable symbols <super> the superclass (default is Object) returns the new class object :answer <msg> <fargs> <code> ADD A MESSAGE TO A CLASS <msg> the message symbol <fargs> the formal argument list (lambda list) <code> a list of executable expressions returns the object When a new instance of a class is created by sending the message ':new' to an existing class, the message ':isnew' followed by whatever parameters were passed to the ':new' message is sent to the newly created object. When a new class is created by sending the ':new' message to the object 'Class', an optional parameter may be specified indicating the superclass of the new class. If this parameter is omitted, the new class will be a subclass of 'Object'. A class inherits all instance variables, class variables, and methods from its super-class. XLISP SYMBOLS Page 17 SYMBOLS o self - the current object (within a method context) o *obarray* - the object hash table o *standard-input* - the standard input stream o *standard-output* - the standard output stream o *error-output* - the error output stream o *trace-output* - the trace output stream o *debug-io* - the debug i/o stream o *breakenable* - flag controlling entering break loop on errors o *tracelist* - list of names of functions to trace o *tracenable* - enable trace back printout on errors o *tracelimit* - number of levels of trace back information o *evalhook* - user substitute for the evaluator function o *applyhook* - (not yet implemented) o *readtable* - the current readtable o *unbound* - indicator for unbound symbols o *gc-flag* - controls the printing of gc messages o *gc-hook* - function to call after garbage collection o *integer-format* - format for printing integers ("%d" or "%ld") o *float-format* - format for printing floats ("%g") o *print-case* - symbol output case (:upcase or :downcase) There are several symbols maintained by the read/eval/print loop. The symbols '+', '++', and '+++' are bound to the most recent three input expressions. The symbols '*', '**' and '***' are bound to the most recent three results. The symbol '-' is bound to the expression currently being evaluated. It becomes the value of '+' at the end of the evaluation. XLISP EVALUATION FUNCTIONS Page 18 EVALUATION FUNCTIONS (eval <expr>) EVALUATE AN XLISP EXPRESSION <expr> the expression to be evaluated returns the result of evaluating the expression (apply <fun> <args>) APPLY A FUNCTION TO A LIST OF ARGUMENTS <fun> the function to apply (or function symbol) <args> the argument list returns the result of applying the function to the arguments (funcall <fun> <arg>...) CALL A FUNCTION WITH ARGUMENTS <fun> the function to call (or function symbol) <arg> arguments to pass to the function returns the result of calling the function with the arguments (quote <expr>) RETURN AN EXPRESSION UNEVALUATED <expr> the expression to be quoted (quoted) returns <expr> unevaluated (function <expr>) GET THE FUNCTIONAL INTERPRETATION <expr> the symbol or lambda expression (quoted) returns the functional interpretation (backquote <expr>) FILL IN A TEMPLATE <expr> the template returns a copy of the template with comma and comma-at expressions expanded (lambda <args> <expr>...) MAKE A FUNCTION CLOSURE <args> formal argument list (lambda list) (quoted) <expr> expressions of the function body returns the function closure (get-lambda-expression <closure>) GET THE LAMBDA EXPRESSION <closure> the closure returns the original lambda expression (macroexpand <form>) RECURSIVELY EXPAND MACRO CALLS <form> the form to expand returns the macro expansion (macroexpand-1 <form>) EXPAND A MACRO CALL <form> the macro call form returns the macro expansion XLISP SYMBOL FUNCTIONS Page 19 SYMBOL FUNCTIONS (set <sym> <expr>) SET THE VALUE OF A SYMBOL <sym> the symbol being set <expr> the new value returns the new value (setq [<sym> <expr>]...) SET THE VALUE OF A SYMBOL <sym> the symbol being set (quoted) <expr> the new value returns the new value (psetq [<sym> <expr>]...) PARALLEL VERSION OF SETQ <sym> the symbol being set (quoted) <expr> the new value returns the new value (setf [<place> <expr>]...) SET THE VALUE OF A FIELD <place> the field specifier (quoted): <sym> set value of a symbol (car <expr>) set car of a cons node (cdr <expr>) set cdr of a cons node (nth <n> <expr>) set nth car of a list (aref <expr> <n>) set nth element of an array (get <sym> <prop>) set value of a property (symbol-value <sym>) set value of a symbol (symbol-function <sym>) set functional value of a symbol (symbol-plist <sym>) set property list of a symbol <value> the new value returns the new value (defun <sym> <fargs> <expr>...) DEFINE A FUNCTION (defmacro <sym> <fargs> <expr>...) DEFINE A MACRO <sym> symbol being defined (quoted) <fargs> formal argument list (lambda list) (quoted) <expr> expressions constituting the body of the function (quoted) returns the function symbol (gensym [<tag>]) GENERATE A SYMBOL <tag> string or number returns the new symbol (intern <pname>) MAKE AN INTERNED SYMBOL <pname> the symbol's print name string returns the new symbol (make-symbol <pname>) MAKE AN UNINTERNED SYMBOL <pname> the symbol's print name string returns the new symbol (symbol-name <sym>) GET THE PRINT NAME OF A SYMBOL <sym> the symbol returns the symbol's print name XLISP SYMBOL FUNCTIONS Page 20 (symbol-value <sym>) GET THE VALUE OF A SYMBOL <sym> the symbol returns the symbol's value (symbol-function <sym>) GET THE FUNCTIONAL VALUE OF A SYMBOL <sym> the symbol returns the symbol's functional value (symbol-plist <sym>) GET THE PROPERTY LIST OF A SYMBOL <sym> the symbol returns the symbol's property list (hash <sym> <n>) COMPUTE THE HASH INDEX FOR A SYMBOL <sym> the symbol or string <n> the table size (integer) returns the hash index (integer) XLISP PROPERTY LIST FUNCTIONS Page 21 PROPERTY LIST FUNCTIONS (get <sym> <prop>) GET THE VALUE OF A PROPERTY <sym> the symbol <prop> the property symbol returns the property value or nil (putprop <sym> <val> <prop>) PUT A PROPERTY ONTO A PROPERTY LIST <sym> the symbol <val> the property value <prop> the property symbol returns the property value (remprop <sym> <prop>) REMOVE A PROPERTY <sym> the symbol <prop> the property symbol returns nil XLISP ARRAY FUNCTIONS Page 22 ARRAY FUNCTIONS (aref <array> <n>) GET THE NTH ELEMENT OF AN ARRAY <array> the array <n> the array index (integer) returns the value of the array element (make-array <size>) MAKE A NEW ARRAY <size> the size of the new array (integer) returns the new array (vector <expr>...) MAKE AN INITIALIZED VECTOR <expr> the vector elements returns the new vector XLISP LIST FUNCTIONS Page 23 LIST FUNCTIONS (car <expr>) RETURN THE CAR OF A LIST NODE <expr> the list node returns the car of the list node (cdr <expr>) RETURN THE CDR OF A LIST NODE <expr> the list node returns the cdr of the list node (cxxr <expr>) ALL CxxR COMBINATIONS (cxxxr <expr>) ALL CxxxR COMBINATIONS (cxxxxr <expr>) ALL CxxxxR COMBINATIONS (first <expr>) A SYNONYM FOR CAR (second <expr>) A SYNONYM FOR CADR (third <expr>) A SYNONYM FOR CADDR (fourth <expr>) A SYNONYM FOR CADDDR (rest <expr>) A SYNONYM FOR CDR (cons <expr1> <expr2>) CONSTRUCT A NEW LIST NODE <expr1> the car of the new list node <expr2> the cdr of the new list node returns the new list node (list <expr>...) CREATE A LIST OF VALUES <expr> expressions to be combined into a list returns the new list (append <expr>...) APPEND LISTS <expr> lists whose elements are to be appended returns the new list (reverse <expr>) REVERSE A LIST <expr> the list to reverse returns a new list in the reverse order (last <list>) RETURN THE LAST LIST NODE OF A LIST <list> the list returns the last list node in the list (member <expr> <list> &key :test :test-not) FIND AN EXPRESSION IN A LIST <expr> the expression to find <list> the list to search :test the test function (defaults to eql) :test-not the test function (sense inverted) returns the remainder of the list starting with the expression (assoc <expr> <alist> &key :test :test-not) FIND AN EXPRESSION IN AN A-LIST <expr> the expression to find <alist> the association list :test the test function (defaults to eql) :test-not the test function (sense inverted) returns the alist entry or nil XLISP LIST FUNCTIONS Page 24 (remove <expr> <list> &key :test :test-not) REMOVE ELEMENTS FROM A LIST <expr> the element to remove <list> the list :test the test function (defaults to eql) :test-not the test function (sense inverted) returns copy of list with matching expressions removed (remove-if <test> <list>) REMOVE ELEMENTS THAT PASS TEST <test> the test predicate <list> the list returns copy of list with matching elements removed (remove-if-not <test> <list>) REMOVE ELEMENTS THAT FAIL TEST <test> the test predicate <list> the list returns copy of list with non-matching elements removed (length <expr>) FIND THE LENGTH OF A LIST, VECTOR OR STRING <expr> the list, vector or string returns the length of the list, vector or string (nth <n> <list>) RETURN THE NTH ELEMENT OF A LIST <n> the number of the element to return (zero origin) <list> the list returns the nth element or nil if the list isn't that long (nthcdr <n> <list>) RETURN THE NTH CDR OF A LIST <n> the number of the element to return (zero origin) <list> the list returns the nth cdr or nil if the list isn't that long (mapc <fcn> <list1> <list>...) APPLY FUNCTION TO SUCCESSIVE CARS <fcn> the function or function name <listn> a list for each argument of the function returns the first list of arguments (mapcar <fcn> <list1> <list>...) APPLY FUNCTION TO SUCCESSIVE CARS <fcn> the function or function name <listn> a list for each argument of the function returns a list of the values returned (mapl <fcn> <list1> <list>...) APPLY FUNCTION TO SUCCESSIVE CDRS <fcn> the function or function name <listn> a list for each argument of the function returns the first list of arguments (maplist <fcn> <list1> <list>...) APPLY FUNCTION TO SUCCESSIVE CDRS <fcn> the function or function name <listn> a list for each argument of the function returns a list of the values returned XLISP LIST FUNCTIONS Page 25 (subst <to> <from> <expr> &key :test :test-not) SUBSTITUTE EXPRESSIONS <to> the new expression <from> the old expression <expr> the expression in which to do the substitutions :test the test function (defaults to eql) :test-not the test function (sense inverted) returns the expression with substitutions (sublis <alist> <expr> &key :test :test-not) SUBSTITUTE WITH AN A-LIST <alist> the association list <expr> the expression in which to do the substitutions :test the test function (defaults to eql) :test-not the test function (sense inverted) returns the expression with substitutions XLISP DESTRUCTIVE LIST FUNCTIONS Page 26 DESTRUCTIVE LIST FUNCTIONS (rplaca <list> <expr>) REPLACE THE CAR OF A LIST NODE <list> the list node <expr> the new value for the car of the list node returns the list node after updating the car (rplacd <list> <expr>) REPLACE THE CDR OF A LIST NODE <list> the list node <expr> the new value for the cdr of the list node returns the list node after updating the cdr (nconc <list>...) DESTRUCTIVELY CONCATENATE LISTS <list> lists to concatenate returns the result of concatenating the lists (delete <expr> &key :test :test-not) DELETE ELEMENTS FROM A LIST <expr> the element to delete <list> the list :test the test function (defaults to eql) :test-not the test function (sense inverted) returns the list with the matching expressions deleted (delete-if <test> <list>) DELETE ELEMENTS THAT PASS TEST <test> the test predicate <list> the list returns the list with matching elements deleted (delete-if-not <test> <list>) DELETE ELEMENTS THAT FAIL TEST <test> the test predicate <list> the list returns the list with non-matching elements deleted (sort <list> <test>) SORT A LIST <list> the list to sort <test> the comparison function returns the sorted list XLISP PREDICATE FUNCTIONS Page 27 PREDICATE FUNCTIONS (atom <expr>) IS THIS AN ATOM? <expr> the expression to check returns t if the value is an atom, nil otherwise (symbolp <expr>) IS THIS A SYMBOL? <expr> the expression to check returns t if the expression is a symbol, nil otherwise (numberp <expr>) IS THIS A NUMBER? <expr> the expression to check returns t if the expression is a number, nil otherwise (null <expr>) IS THIS AN EMPTY LIST? <expr> the list to check returns t if the list is empty, nil otherwise (not <expr>) IS THIS FALSE? <expr> the expression to check return t if the value is nil, nil otherwise (listp <expr>) IS THIS A LIST? <expr> the expression to check returns t if the value is a cons or nil, nil otherwise (endp <list>) IS THIS THE END OF A LIST <list> the list returns t if the value is nil, nil otherwise (consp <expr>) IS THIS A NON-EMPTY LIST? <expr> the expression to check returns t if the value is a cons, nil otherwise (integerp <expr>) IS THIS AN INTEGER? <expr> the expression to check returns t if the value is an integer, nil otherwise (floatp <expr>) IS THIS A FLOAT? <expr> the expression to check returns t if the value is a float, nil otherwise (stringp <expr>) IS THIS A STRING? <expr> the expression to check returns t if the value is a string, nil otherwise (characterp <expr>) IS THIS A CHARACTER? <expr> the expression to check returns t if the value is a character, nil otherwise (arrayp <expr>) IS THIS AN ARRAY? <expr> the expression to check returns t if the value is an array, nil otherwise XLISP PREDICATE FUNCTIONS Page 28 (streamp <expr>) IS THIS A STREAM? <expr> the expression to check returns t if the value is a stream, nil otherwise (objectp <expr>) IS THIS AN OBJECT? <expr> the expression to check returns t if the value is an object, nil otherwise (boundp <sym>) IS A VALUE BOUND TO THIS SYMBOL? <sym> the symbol returns t if a value is bound to the symbol, nil otherwise (fboundp <sym>) IS A FUNCTIONAL VALUE BOUND TO THIS SYMBOL? <sym> the symbol returns t if a functional value is bound to the symbol, nil otherwise (minusp <expr>) IS THIS NUMBER NEGATIVE? <expr> the number to test returns t if the number is negative, nil otherwise (zerop <expr>) IS THIS NUMBER ZERO? <expr> the number to test returns t if the number is zero, nil otherwise (plusp <expr>) IS THIS NUMBER POSITIVE? <expr> the number to test returns t if the number is positive, nil otherwise (evenp <expr>) IS THIS INTEGER EVEN? <expr> the integer to test returns t if the integer is even, nil otherwise (oddp <expr>) IS THIS INTEGER ODD? <expr> the integer to test returns t if the integer is odd, nil otherwise (eq <expr1> <expr2>) ARE THE EXPRESSIONS IDENTICAL? <expr1> the first expression <expr2> the second expression returns t if they are equal, nil otherwise (eql <expr1> <expr2>) ARE THE EXPRESSIONS IDENTICAL? (WORKS WITH ALL NUMBERS) <expr1> the first expression <expr2> the second expression returns t if they are equal, nil otherwise (equal <expr1> <expr2>) ARE THE EXPRESSIONS EQUAL? <expr1> the first expression <expr2> the second expression returns t if they are equal, nil otherwise XLISP CONTROL CONSTRUCTS Page 29 CONTROL CONSTRUCTS (cond <pair>...) EVALUATE CONDITIONALLY <pair> pair consisting of: (<pred> <expr>...) where <pred> is a predicate expression <expr> evaluated if the predicate is not nil returns the value of the first expression whose predicate is not nil (and <expr>...) THE LOGICAL AND OF A LIST OF EXPRESSIONS <expr> the expressions to be ANDed returns nil if any expression evaluates to nil, otherwise the value of the last expression (evaluation of expressions stops after the first expression that evaluates to nil) (or <expr>...) THE LOGICAL OR OF A LIST OF EXPRESSIONS <expr> the expressions to be ORed returns nil if all expressions evaluate to nil, otherwise the value of the first non-nil expression (evaluation of expressions stops after the first expression that does not evaluate to nil) (if <texpr> <expr1> [<expr2>]) EVALUATE EXPRESSIONS CONDITIONALLY <texpr> the test expression <expr1> the expression to be evaluated if texpr is non-nil <expr2> the expression to be evaluated if texpr is nil returns the value of the selected expression (when <texpr> <expr>...) EVALUATE ONLY WHEN A CONDITION IS TRUE <texpr> the test expression <expr> the expression(s) to be evaluted if texpr is non-nil returns the value of the last expression or nil (unless <texpr> <expr>...) EVALUATE ONLY WHEN A CONDITION IS FALSE <texpr> the test expression <expr> the expression(s) to be evaluated if texpr is nil returns the value of the last expression or nil (case <expr> <case>...) SELECT BY CASE <expr> the selection expression <case> pair consisting of: (<value> <expr>...) where: <value> is a single expression or a list of expressions (unevaluated) <expr> are expressions to execute if the case matches returns the value of the last expression of the matching case XLISP CONTROL CONSTRUCTS Page 30 (let (<binding>...) <expr>...) CREATE LOCAL BINDINGS (let* (<binding>...) <expr>...) LET WITH SEQUENTIAL BINDING <binding> the variable bindings each of which is either: 1) a symbol (which is initialized to nil) 2) a list whose car is a symbol and whose cadr is an initialization expression <expr> the expressions to be evaluated returns the value of the last expression (flet (<binding>...) <expr>...) CREATE LOCAL FUNCTIONS (labels (<binding>...) <expr>...) FLET WITH RECURSIVE FUNCTIONS (macrolet (<binding>...) <expr>...) CREATE LOCAL MACROS <binding> the function bindings each of which is: (<sym> <fargs> <expr>...) where: <sym> the function/macro name <fargs> formal argument list (lambda list) <expr> expressions constituting the body of the function/macro <expr> the expressions to be evaluated returns the value of the last expression (catch <sym> <expr>...) EVALUATE EXPRESSIONS AND CATCH THROWS <sym> the catch tag <expr> expressions to evaluate returns the value of the last expression the throw expression (throw <sym> [<expr>]) THROW TO A CATCH <sym> the catch tag <expr> the value for the catch to return (defaults to nil) returns never returns (unwind-protect <expr> <cexpr>...) PROTECT EVALUATION OF AN EXPRESSION <expr> the expression to protect <cexpr> the cleanup expressions returns the value of the expression Note: unwind-protect guarantees to execute the cleanup expressions even if a non-local exit terminates the evaluation of the protected expression XLISP LOOPING CONSTRUCTS Page 31 LOOPING CONSTRUCTS (loop <expr>...) BASIC LOOPING FORM <expr> the body of the loop returns never returns (must use non-local exit) (do (<binding>...) (<texpr> <rexpr>...) <expr>...) (do* (<binding>...) (<texpr> <rexpr>...) <expr>...) <binding> the variable bindings each of which is either: 1) a symbol (which is initialized to nil) 2) a list of the form: (<sym> <init> [<step>]) where: <sym> is the symbol to bind <init> is the initial value of the symbol <step> is a step expression <texpr> the termination test expression <rexpr> result expressions (the default is nil) <expr> the body of the loop (treated like an implicit prog) returns the value of the last result expression (dolist (<sym> <expr> [<rexpr>]) <expr>...) LOOP THROUGH A LIST <sym> the symbol to bind to each list element <expr> the list expression <rexpr> the result expression (the default is nil) <expr> the body of the loop (treated like an implicit prog) (dotimes (<sym> <expr> [<rexpr>]) <expr>...) LOOP FROM ZERO TO N-1 <sym> the symbol to bind to each value from 0 to n-1 <expr> the number of times to loop <rexpr> the result expression (the default is nil) <expr> the body of the loop (treated like an implicit prog) XLISP THE PROGRAM FEATURE Page 32 THE PROGRAM FEATURE (prog (<binding>...) <expr>...) THE PROGRAM FEATURE (prog* (<binding>...) <expr>...) PROG WITH SEQUENTIAL BINDING <binding> the variable bindings each of which is either: 1) a symbol (which is initialized to nil) 2) a list whose car is a symbol and whose cadr is an initialization expression <expr> expressions to evaluate or tags (symbols) returns nil or the argument passed to the return function (block <name> <expr>...) NAMED BLOCK <name> the block name (symbol) <expr> the block body returns the value of the last expression (return [<expr>]) CAUSE A PROG CONSTRUCT TO RETURN A VALUE <expr> the value (defaults to nil) returns never returns (return-from <name> [<value>]) RETURN FROM A NAMED BLOCK <name> the block name (symbol) <value> the value to return (defaults to nil) returns never returns (tagbody <expr>...) BLOCK WITH LABELS <expr> expression(s) to evaluate or tags (symbols) returns nil (go <sym>) GO TO A TAG WITHIN A TAGBODY OR PROG <sym> the tag (quoted) returns never returns (progv <slist> <vlist> <expr>...) DYNAMICALLY BIND SYMBOLS <slist> list of symbols <vlist> list of values to bind to the symbols <expr> expression(s) to evaluate returns the value of the last expression (prog1 <expr1> <expr>...) EXECUTE EXPRESSIONS SEQUENTIALLY <expr1> the first expression to evaluate <expr> the remaining expressions to evaluate returns the value of the first expression (prog2 <expr1> <expr2> <expr>...) EXECUTE EXPRESSIONS SEQUENTIALLY <expr1> the first expression to evaluate <expr2> the second expression to evaluate <expr> the remaining expressions to evaluate returns the value of the second expression (progn <expr>...) EXECUTE EXPRESSIONS SEQUENTIALLY <expr> the expressions to evaluate returns the value of the last expression (or nil) XLISP DEBUGGING AND ERROR HANDLING Page 33 DEBUGGING AND ERROR HANDLING (trace <sym>) ADD A FUNCTION TO THE TRACE LIST <sym> the function to add (quoted) returns the trace list (untrace <sym>) REMOVE A FUNCTION FROM THE TRACE LIST <sym> the function to remove (quoted) returns the trace list (error <emsg> [<arg>]) SIGNAL A NON-CORRECTABLE ERROR <emsg> the error message string <arg> the argument expression (printed after the message) returns never returns (cerror <cmsg> <emsg> [<arg>]) SIGNAL A CORRECTABLE ERROR <cmsg> the continue message string <emsg> the error message string <arg> the argument expression (printed after the message) returns nil when continued from the break loop (break [<bmsg> [<arg>]]) ENTER A BREAK LOOP <bmsg> the break message string (defaults to "**BREAK**") <arg> the argument expression (printed after the message) returns nil when continued from the break loop (clean-up) CLEAN-UP AFTER AN ERROR returns never returns (top-level) CLEAN-UP AFTER AN ERROR AND RETURN TO THE TOP LEVEL returns never returns (continue) CONTINUE FROM A CORRECTABLE ERROR returns never returns (errset <expr> [<pflag>]) TRAP ERRORS <expr> the expression to execute <pflag> flag to control printing of the error message returns the value of the last expression consed with nil or nil on error (baktrace [<n>]) PRINT N LEVELS OF TRACE BACK INFORMATION <n> the number of levels (defaults to all levels) returns nil (evalhook <expr> <ehook> <ahook> [<env>]) EVALUATE WITH HOOKS <expr> the expression to evaluate <ehook> the value for *evalhook* <ahook> the value for *applyhook* <env> the environment (default is nil) returns the result of evaluating the expression XLISP ARITHMETIC FUNCTIONS Page 34 ARITHMETIC FUNCTIONS (truncate <expr>) TRUNCATES A FLOATING POINT NUMBER TO AN INTEGER <expr> the number returns the result of truncating the number (float <expr>) CONVERTS AN INTEGER TO A FLOATING POINT NUMBER <expr> the number returns the result of floating the integer (+ <expr>...) ADD A LIST OF NUMBERS <expr> the numbers returns the result of the addition (- <expr>...) SUBTRACT A LIST OF NUMBERS OR NEGATE A SINGLE NUMBER <expr> the numbers returns the result of the subtraction (* <expr>...) MULTIPLY A LIST OF NUMBERS <expr> the numbers returns the result of the multiplication (/ <expr>...) DIVIDE A LIST OF NUMBERS <expr> the numbers returns the result of the division (1+ <expr>) ADD ONE TO A NUMBER <expr> the number returns the number plus one (1- <expr>) SUBTRACT ONE FROM A NUMBER <expr> the number returns the number minus one (rem <expr>...) REMAINDER OF A LIST OF NUMBERS <expr> the numbers returns the result of the remainder operation (min <expr>...) THE SMALLEST OF A LIST OF NUMBERS <expr> the expressions to be checked returns the smallest number in the list (max <expr>...) THE LARGEST OF A LIST OF NUMBERS <expr> the expressions to be checked returns the largest number in the list (abs <expr>) THE ABSOLUTE VALUE OF A NUMBER <expr> the number returns the absolute value of the number (gcd <n1> <n2>...) COMPUTE THE GREATEST COMMON DIVISOR <n1> the first number (integer) <n2> the second number(s) (integer) returns the greatest common divisor XLISP ARITHMETIC FUNCTIONS Page 35 (random <n>) COMPUTE A RANDOM NUMBER BETWEEN 1 and N-1 <n> the upper bound (integer) returns a random number (sin <expr>) COMPUTE THE SINE OF A NUMBER <expr> the floating point number returns the sine of the number (cos <expr>) COMPUTE THE COSINE OF A NUMBER <expr> the floating point number returns the cosine of the number (tan <expr>) COMPUTE THE TANGENT OF A NUMBER <expr> the floating point number returns the tangent of the number (expt <x-expr> <y-expr>) COMPUTE X TO THE Y POWER <x-expr> the floating point number <y-expr> the floating point exponent returns x to the y power (exp <x-expr>) COMPUTE E TO THE X POWER <x-expr> the floating point number returns e to the x power (sqrt <expr>) COMPUTE THE SQUARE ROOT OF A NUMBER <expr> the floating point number returns the square root of the number (< <n1> <n2>...) TEST FOR LESS THAN (<= <n1> <n2>...) TEST FOR LESS THAN OR EQUAL TO (= <n1> <n2>...) TEST FOR EQUAL TO (/= <n1> <n2>...) TEST FOR NOT EQUAL TO (>= <n1> <n2>...) TEST FOR GREATER THAN OR EQUAL TO (> <n1> <n2>...) TEST FOR GREATER THAN <n1> the first number to compare <n2> the second number to compare returns the result of comparing <n1> with <n2>... XLISP BITWISE LOGICAL FUNCTIONS Page 36 BITWISE LOGICAL FUNCTIONS (logand <expr>...) THE BITWISE AND OF A LIST OF NUMBERS <expr> the numbers returns the result of the and operation (logior <expr>...) THE BITWISE INCLUSIVE OR OF A LIST OF NUMBERS <expr> the numbers returns the result of the inclusive or operation (logxor <expr>...) THE BITWISE EXCLUSIVE OR OF A LIST OF NUMBERS <expr> the numbers returns the result of the exclusive or operation (lognot <expr>) THE BITWISE NOT OF A NUMBER <expr> the number returns the bitwise inversion of number XLISP STRING FUNCTIONS Page 37 STRING FUNCTIONS (string <expr>) MAKE A STRING FROM AN INTEGER ASCII VALUE <expr> the integer returns a one character string (string-trim <bag> <str>) TRIM BOTH ENDS OF A STRING <bag> a string containing characters to trim <str> the string to trim returns a trimed copy of the string (string-left-trim <bag> <str>) TRIM THE LEFT END OF A STRING <bag> a string containing characters to trim <str> the string to trim returns a trimed copy of the string (string-right-trim <bag> <str>) TRIM THE RIGHT END OF A STRING <bag> a string containing characters to trim <str> the string to trim returns a trimed copy of the string (string-upcase <str> &key :start :end) CONVERT TO UPPERCASE <str> the string :start the starting offset :end the ending offset + 1 returns a converted copy of the string (string-downcase <str> &key :start :end) CONVERT TO LOWERCASE <str> the string :start the starting offset :end the ending offset + 1 returns a converted copy of the string (nstring-upcase <str> &key :start :end) CONVERT TO UPPERCASE <str> the string :start the starting offset :end the ending offset + 1 returns the converted string (not a copy) (nstring-downcase <str> &key :start :end) CONVERT TO LOWERCASE <str> the string :start the starting offset :end the ending offset + 1 returns the converted string (not a copy) (strcat <expr>...) CONCATENATE STRINGS <expr> the strings to concatenate returns the result of concatenating the strings (subseq <string> <start> [<end>]) EXTRACT A SUBSTRING <string> the string <start> the starting position (zero origin) <end> the ending position + 1 (defaults to end) returns substring between <start> and <end> XLISP STRING FUNCTIONS Page 38 (string< <str1> <str2> &key :start1 :end1 :start2 :end2) (string<= <str1> <str2> &key :start1 :end1 :start2 :end2) (string= <str1> <str2> &key :start1 :end1 :start2 :end2) (string/= <str1> <str2> &key :start1 :end1 :start2 :end2) (string>= <str1> <str2> &key :start1 :end1 :start2 :end2) (string> <str1> <str2> &key :start1 :end1 :start2 :end2) <str1> the first string to compare <str2> the second string to compare :start1 first substring starting offset :end1 first substring ending offset + 1 :start2 second substring starting offset :end2 second substring ending offset + 1 returns t if predicate is true, nil otherwise Note: case is significant with these comparison functions. (string-lessp <str1> <str2> &key :start1 :end1 :start2 :end2) (string-not-greaterp <str1> <str2> &key :start1 :end1 :start2 :end2) (string-equalp <str1> <str2> &key :start1 :end1 :start2 :end2) (string-not-equalp <str1> <str2> &key :start1 :end1 :start2 :end2) (string-not-lessp <str1> <str2> &key :start1 :end1 :start2 :end2) (string-greaterp <str1> <str2> &key :start1 :end1 :start2 :end2) <str1> the first string to compare <str2> the second string to compare :start1 first substring starting offset :end1 first substring ending offset + 1 :start2 second substring starting offset :end2 second substring ending offset + 1 returns t if predicate is true, nil otherwise Note: case is not significant with these comparison functions. XLISP CHARACTER FUNCTIONS Page 39 CHARACTER FUNCTIONS (char <string> <index>) EXTRACT A CHARACTER FROM A STRING <string> the string <index> the string index (zero relative) returns the ascii code of the character (upper-case-p <chr>) IS THIS AN UPPER CASE CHARACTER? <chr> the character returns true if the character is upper case, nil otherwise (lower-case-p <chr>) IS THIS A LOWER CASE CHARACTER? <chr> the character returns true if the character is lower case, nil otherwise (both-case-p <chr>) IS THIS AN ALPHABETIC (EITHER CASE) CHARACTER? <chr> the character returns true if the character is alphabetic, nil otherwise (digit-char-p <chr>) IS THIS A DIGIT CHARACTER? <chr> the character returns the digit weight if character is a digit, nil otherwise (char-code <chr>) GET THE ASCII CODE OF A CHARACTER <chr> the character returns the ASCII character code (integer) (code-char <code>) GET THE CHARACTER WITH A SPECFIED ASCII CODE <code> the ASCII code (integer) returns the character with that code or nil (char-upcase <chr>) CONVERT A CHARACTER TO UPPER CASE <chr> the character returns the upper case character (char-downcase <chr>) CONVERT A CHARACTER TO LOWER CASE <chr> the character returns the lower case character (digit-char <n>) CONVERT A DIGIT WEIGHT TO A DIGIT <n> the digit weight (integer) returns the digit character or nil (char-int <chr>) CONVERT A CHARACTER TO AN INTEGER <chr> the character returns the ASCII character code (int-char <int>) CONVERT AN INTEGER TO A CHARACTER <int> the ASCII character code returns the character with that code XLISP CHARACTER FUNCTIONS Page 40 (char< <chr1> <chr2>...) (char<= <chr1> <chr2>...) (char= <chr1> <chr2>...) (char/= <chr1> <chr2>...) (char>= <chr1> <chr2>...) (char> <chr1> <chr2>...) <chr1> the first character to compare <chr2> the second character(s) to compare returns t if predicate is true, nil otherwise Note: case is significant with these comparison functions. (char-lessp <chr1> <chr2>...) (char-not-greaterp <chr1> <chr2>...) (char-equalp <chr1> <chr2>...) (char-not-equalp <chr1> <chr2>...) (char-not-lessp <chr1> <chr2>...) (char-greaterp <chr1> <chr2>...) <chr1> the first string to compare <chr2> the second string(s) to compare returns t if predicate is true, nil otherwise Note: case is not significant with these comparison functions. XLISP INPUT/OUTPUT FUNCTIONS Page 41 INPUT/OUTPUT FUNCTIONS (read [<stream> [<eof> [<rflag>]]]) READ AN EXPRESSION <stream> the input stream (default is standard input) <eof> the value to return on end of file (default is nil) <rflag> recursive read flag (default is nil) returns the expression read (print <expr> [<stream>]) PRINT AN EXPRESSION ON A NEW LINE <expr> the expression to be printed <stream> the output stream (default is standard output) returns the expression (prin1 <expr> [<stream>]) PRINT AN EXPRESSION <expr> the expression to be printed <stream> the output stream (default is standard output) returns the expression (princ <expr> [<stream>]) PRINT AN EXPRESSION WITHOUT QUOTING <expr> the expressions to be printed <stream> the output stream (default is standard output) returns the expression (pprint <expr> [<stream>]) PRETTY PRINT AN EXPRESSION <expr> the expressions to be printed <stream> the output stream (default is standard output) returns the expression (terpri [<stream>]) TERMINATE THE CURRENT PRINT LINE <stream> the output stream (default is standard output) returns nil (flatsize <expr>) LENGTH OF PRINTED REPRESENTATION USING PRIN1 <expr> the expression returns the length (flatc <expr>) LENGTH OF PRINTED REPRESENTATION USING PRINC <expr> the expression returns the length XLISP THE FORMAT FUNCTION Page 42 THE FORMAT FUNCTION (format <stream> <fmt> <arg>...) DO FORMATTED OUTPUT <stream> the output stream <fmt> the format string <arg> the format arguments returns output string if <stream> is nil, nil otherwise The format string can contain characters that should be copied directly to the output and formatting directives. The formatting directives are: ~A print next argument using princ ~S print next argument using prin1 ~% start a new line ~~ print a tilde character XLISP FILE I/O FUNCTIONS Page 43 FILE I/O FUNCTIONS (open <fname> &key :direction) OPEN A FILE STREAM <fname> the file name string or symbol :direction :input or :output (default is :input) returns a stream (close <stream>) CLOSE A FILE STREAM <stream> the stream returns nil (read-char [<stream>]) READ A CHARACTER FROM A STREAM <stream> the input stream (default is standard input) returns the character (peek-char [<flag> [<stream>]]) PEEK AT THE NEXT CHARACTER <flag> flag for skipping white space (default is nil) <stream> the input stream (default is standard input) returns the character (integer) (write-char <ch> [<stream>]) WRITE A CHARACTER TO A STREAM <ch> the character to write <stream> the output stream (default is standard output) returns the character (read-line [<stream>]) READ A LINE FROM A STREAM <stream> the input stream (default is standard input) returns the string (read-byte [<stream>]) READ A BYTE FROM A STREAM <stream> the input stream (default is standard input) returns the byte (integer) (write-byte <byte> [<stream>]) WRITE A BYTE TO A STREAM <byte> the byte to write (integer) <stream> the output stream (default is standard output) returns the byte (integer) XLISP STRING STREAM FUNCTIONS Page 44 STRING STREAM FUNCTIONS These functions operate on unnamed streams. An unnamed output stream collects characters sent to it when it is used as the destination of any output function. The functions 'get-output- stream-string' and string or a list of characters. An unnamed input stream is setup with the 'make-string-input- stream' function and returns each character of the string when it is used as the source of any input function. (make-string-input-stream <str> [<start> [<end>]]) <str> the string <start> the starting offset <end> the ending offset + 1 returns an unnamed stream that reads from the string (make-string-output-stream) returns an unnamed output stream (get-output-stream-string <stream>) <stream> the output stream returns the output so far as a string Note: the output stream is emptied by this function (get-output-stream-list <stream>) <stream> the output stream returns the output so far as a list Note: the output stream is emptied by this function XLISP SYSTEM FUNCTIONS Page 45 SYSTEM FUNCTIONS (load <fname> &key :verbose :print) LOAD A SOURCE FILE <fname> the filename string or symbol :verbose the verbose flag (default is t) :print the print flag (default is nil) returns the filename (save <fname>) SAVE WORKSPACE TO A FILE <fname> the filename string or symbol returns t if workspace was written, nil otherwise (restore <fname>) RESTORE WORKSPACE FROM A FILE <fname> the filename string or symbol returns nil on failure, otherwise never returns (dribble [<fname>]) CREATE A FILE WITH A TRANSCRIPT OF A SESSION <fname> file name string or symbol (if missing, close current transcript) returns t if the transcript is opened, nil if it is closed (gc) FORCE GARBAGE COLLECTION returns nil (expand <num>) EXPAND MEMORY BY ADDING SEGMENTS <num> the number of segments to add returns the number of segments added (alloc <num>) CHANGE NUMBER OF NODES TO ALLOCATE IN EACH SEGMENT <num> the number of nodes to allocate returns the old number of nodes to allocate (room) SHOW MEMORY ALLOCATION STATISTICS returns nil (type-of <expr>) RETURNS THE TYPE OF THE EXPRESSION <expr> the expression to return the type of returns nil if the value is nil otherwise one of the symbols: SYMBOL for symbols OBJECT for objects CONS for conses SUBR for built-in functions FSUBR for special forms CLOSURE for defined functions STRING for strings FIXNUM for integers FLONUM for floating point numbers CHARACTER for characters FILE-STREAM for file pointers UNNAMED-STREAM for unnamed streams ARRAY for arrays XLISP SYSTEM FUNCTIONS Page 46 (peek <addrs>) PEEK AT A LOCATION IN MEMORY <addrs> the address to peek at (integer) returns the value at the specified address (integer) (poke <addrs> <value>) POKE A VALUE INTO MEMORY <addrs> the address to poke (integer) <value> the value to poke into the address (integer) returns the value (address-of <expr>) GET THE ADDRESS OF AN XLISP NODE <expr> the node returns the address of the node (integer) (exit) EXIT XLISP returns never returns XLISP EXAMPLES Page 47 FILE I/O FUNCTIONS Input from a File To open a file for input, use the OPEN function with the keyword argument :DIRECTION set to :INPUT. To open a file for output, use the OPEN function with the keyword argument :DIRECTION set to :OUTPUT. The OPEN function takes a single required argument which is the name of the file to be opened. This name can be in the form of a string or a symbol. The OPEN function returns an object of type FILE-STREAM if it succeeds in opening the specified file. It returns the value NIL if it fails. In order to manipulate the file, it is necessary to save the value returned by the OPEN function. This is usually done by assigning it to a variable with the SETQ special form or by binding it using LET or LET*. Here is an example: (setq fp (open "init.lsp" :direction :input)) Evaluating this expression will result in the file "init.lsp" being opened. The file object that will be returned by the OPEN function will be assigned to the variable "fp". It is now possible to use the file for input. To read an expression from the file, just supply the value of the "fp" variable as the optional "stream" argument to READ. (read fp) Evaluating this expression will result in reading the first expression from the file "init.lsp". The expression will be returned as the result of the READ function. More expressions can be read from the file using further calls to the READ function. When there are no more expressions to read, the READ function will return NIL (or whatever value was supplied as the second argument to READ). Once you are done reading from the file, you should close it. To close the file, use the following expression: (close fp) Evaluating this expression will cause the file to be closed. XLISP EXAMPLES Page 48 Output to a File Writing to a file is pretty much the same as reading from one. You need to open the file first. This time you should use the OPEN function to indicate that you will do output to the file. For example: (setq fp (open "test.dat" :direction :output)) Evaluating this expression will open the file "test.dat" for output. If the file already exists, its current contents will be discarded. If it doesn't already exist, it will be created. In any case, a FILE-STREAM object will be returned by the OPEN function. This file object will be assigned to the "fp" variable. It is now possible to write to this file by supplying the value of the "fp" variable as the optional "stream" parameter in the PRINT function. (print "Hello there" fp) Evaluating this expression will result in the string "Hello there" being written to the file "test.dat". More data can be written to the file using the same technique. Once you are done writing to the file, you should close it. Closing an output file is just like closing an input file. (close fp) Evaluating this expression will close the output file and make it permanent. XLISP EXAMPLES Page 49 A Slightly More Complicated File Example This example shows how to open a file, read each Lisp expression from the file and print it. It demonstrates the use of files and the use of the optional "stream" argument to the READ function. 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