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Scheme In One Define. The garbage collector, the name and other parts of this program are * COPYRIGHT (c) 1989 BY * * PARADIGM ASSOCIATES INCORPORATED, CAMBRIDGE, MASSACHUSETTS. * Conversion to full scheme standard, characters, vectors, ports, complex & rational numbers, and other major enhancments by * Scaglione Ermanno, v. Pirinoli 16 IMPERIA P.M. 18100 ITALY * Permission to use, copy, modify, distribute and sell this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation, and that the name of Paradigm Associates Inc not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. PARADIGM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL PARADIGM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. Siod is an interpreter for the algoritmic language SCHEME; the standard followed in the implementation is described in "TI Scheme Language Reference Manual" and follows the "Revised Revised Report on Scheme". Sorry the "Revised 3-rd Report on Scheme" is not available to me and therefore I can not update Siod. Siod is a pure interpreter and no compilation is performed, and so the evaluation, especially of complex procedures is very slow even if it requires only a small amount of memory to run. Siod checks always the type of objects before perform operation on them, the ispector allows the user to examine the contents of the stack frame and the environment in effect when an error or a breakpoint is entered and only a few procedures are implemented via macro, so errors can be easily individuated even if there isn't a stack frame backtrace. These features makes Siod an ideal tool to learn Scheme and functional programming. There isn't an esplicit control of evaluation and therefore Siod requires a well dimensioned stack to work. On AMIGA an abnormal termination error is performed in case of stack overflow. Other major problems on version 2.6: Bignum isn't implemented, integers are stored in a C-long until they overflows and then they are automatically stored in a C-double (numbers in siod are automatically stored in lowest type that can contain them with the minimum loss of information). There aren't breakpoint levels, when an error occours the inspector is invoked and then a reset is performed. Continuation aren't handled in the rigth way and are implemented in term of the Common-LISP-like *throw and *catch procedures, and so they hasn't an unlimited extent as prescribed by the standard but are valid only inside the procedure invoked by call/cc. Every reset reinitializes the *catch list and every *throw deletes all the *catch's that were set after the corrispondent one was. Resets and errors can be intercepted by the user via the non-standard call-on-reset procedure. Currently the procedures with-input-from-file and with-output-to-file are implemented using this mechanism and therefore if you escape from the procedure using call/cc or *throw the file isn't closed and the current input or output isn't restored until the next reset or error. Siod uses a fixed size heap and its performances depends on the C stack. Siod's memory unit is called cons and is 10 bytes long, every scheme object is contained in a cons, and all the symbols with the same printed representation refers to the same cons (are interned). The number of cons available to Siod cannot be changed during the session due to a dirty mechanism of garbage collection, heritage of the original Paradigm code. Siod can be run with a really small amount of memory to the cost of frequent garbage collecting. The discipline of garbage collecting followed is mark & sweep: all the cons allocated are available in a singol heap to the user; no compaction is performed but this isn't a problem on microcomputers. The options available to the user are: -h<number> sets the number of cons in siod's fixed-size heap. Minimum 1000. Default 5000. -o<number> sets the number of buckets in siod's symbols hash table. Minimum 1. Default 100. -f<number> sets the number of buckets in siod's integers hash table. Minimum 1. Default 100. -i<filename> a file to be loaded in the high-speed user-global-environment. -q quiet flag. -s small set of predefined functions. The options can be set also setting environment variables (using the DOS command setenv): SIOD-HEAP-SIZE is equivalent to the -h option SIOD-SYMTAB-SIZE is equivalent to the -o option SIOD-FIXTAB-SIZE is equivalent to the -f option SIOD-INIT-FILE is equivalent to the -i option SIOD-QUIET if set to 1 is equivalent to the -q option SIOD-SMALL if set to 1 is equivalent to the -s option Options settled using environment variables are overrun by the options specified in the command string. Symbols with the same printed representation are stored at the same address using a hash table (symtab), the user-global-environment isn't a proper environment but refers directly to the symbols contained in the hash table, for this reason its bindings cannot be showed even if it can be accessed by the procedures like eval or load. Provided there is a well dimensioned hash table, loading or defining procedures directly in this environment can increase greatly the speed of evaluation depending on the number of procedures defined in the user-initial-environment. The only difference between integers and other numbers is that integers are interned, so two identical integers refers to the same heap cell and therefore can be compared using eq?. This way each integer is stored only once saving memory. Also identical characters are stored at the same address using hash tables. The table for characters has 256 buckets and can contain all the characters of the extended ASCII code, therefore there isn't any collision. The size of the symtab and fixtab can be specified by the user; collisions are handled with the chaining tecnique: symbols and integers hashed to the same bucket are stored into a linear list. Tables too small can reduce greately the speed of evaluation. The procedure eq? used to determine if two objects are identical, gives always the correct answer for interned objects. Uninterned objects can be compared using eqv? or equal?. NOTE: integers that overflows the size of a C-long aren't interned and cannot be compared with eq? even if the integer? predicate returns true. The behaviour of the interpreter during the session is determined by three variables that can be freely modified by the user: siod-debug-mode if set to #t cause the inspector to be invoked after an error; if set to #f a reset is performed. siod-repl-mode if set to #t cause the interpreter to print after the evaluation of each command some information about the memory usage and time needed else only the prompt is printed. siod-gc-mode if set to #t before and after each garbage collection the interpreter prints a message showing also the time needed and the number of cells collected. If siod is started with the -q option these three variables are set to #f otherwise to #t. If siod is started with the -s option only a small number of predefined symbols are defined, and variables such nil true are not defined. This can be useful to run siod with a small number of cons (i.e. 1500) to use it as a powerful calculator. On AMIGA the main program requires about 150k of mem and each cons is 10 bytes long; run siod with -h10000 -o1000 -f500 will require less than 280k and works fine on an old A500 not expanded leaving enough memory to run a good editor in background. Vectors and strings requires additional memory and the big stack size needed must be considered too. The smallest configuration -h1000 -o1 -f1 requires less than 180k to run. A suggested configuration is: stack size 50000, heap size 25000-50000, symtab size 1000-2000, fixtab size 500-5000 (depending on the character of the application to be run). When siod is started with full-set option it looks in the current directory for the file "siod.scm" and loads it in the user-global-environment, then, if specified, loads the init file; if is started with the small-set option loads only the init file. The file "siod.scm" should not be loaded in small-set mode because it requires procedures not defined in that mode, the file small-siod.scm can be loaded or specifiead as init file, providing some useful definition. Part of the runtime library is defined in separate files that are loaded only if necessary. Siod looks for this files in the SIOD: directory that should be correctly assigned. This path can be changed editing the file siod.scm and changing the definition of the variable "path" in the first line this variable is used only inside the file siod.scm and then can be redefined. LANGUAGE DEFINITION x any scheme object n any number r a rational number m a complex number i an integer o a procedure p a port s a string c a character y a symbol e an environment l a list or a pair v a vector {x} an optional argument x ... a list of argument x1 the first arg in the arg-list .... xn the n-th arg in the arg-list <exp> any scheme expression <pred> a scheme expression that returns #t or #f NOTES: constants should not be modified, <exp> is identical to x the use of one or the other indicates the tipical use in that context. Optional arguments of subroutines of types 1 2 3 can be replaced by nil (non standard), basic subroutines are defined also in -s mode, subroutine are available only in full mode, the other are defined in the file siod.scm directly or as autoload-from-file. #\backspace (defined in siod.scm) constant. #\escape (defined in siod.scm) constant. #\newline (defined in siod.scm) constant. #\page (defined in siod.scm) constant. #\return (defined in siod.scm) constant. #\rubout (defined in siod.scm) constant. #\space (defined in siod.scm) constant. #\tab (defined in siod.scm) constant. * (basic subroutine) (* n ... ) multiplies a list of numbers. *the-non-printing-object* (constant) *the-non-printing-object* This is a value that if intercected by the standard scheme-top-level cause it not to print nothing. + (basic subroutine) (+ n ... ) adds a list of numbers. - (basic subroutine) (- n ... ) subtracts a list of numbers. -1+ (basic subroutine) (-1+ n) subtracts 1 from n. Is faster than (- n 1). / (basic subroutine) (/ n ... ) divides a list of numbers. 1+ (basic subroutine) (1+ n) adds 1 to n. Is faster than (+ n 1). < <= <> = > >= (basic subroutine) (op n n) compares two numbers. abs (basic subroutine) (abs n) returns the absolute value of a number. access (subroutine) (access y {e}) returns the value of a symbol in an environment. If no environment is specified the current environment is used. acos (basic subroutine) (acos n) returns the arcosine of a number. add1 (subroutine) (add1 n) adds 1 to its argument. alias (defined in siod.scm) (alias y1 y2) It is a macro that allows the symbol y1 to be used instead of y2 in every contest. and (basic subroutine) (and <exp> ... ) Performs the logical and of a list of expressions. It evaluates the expressions until they evaluates to #t and returns the value returned by the last exp or #f. append (basic subroutine) (append l ... ) Return the list obtained concatenating its arguments. append! (subroutine) (append! l ... ) Return the list obtained destructively concatenating its arguments. apply (subroutine) (apply o l) Evaluates the procedure o with the arguments of l. apply-if (subroutine) (apply-if <pred> o x) Evaluates <pred> and if it returns a non-null value evaluates the procedure o with the result of <preed> as argument. If <pred> is #f returns x. ascii->symbol (subroutine) (ascii->symbol i) Return an interned symbol whose printed representation is the character of ASCII code i. asin (basic subroutine) (asin n) returns the arcosine of a number. assert (defined in siod.scm) (assert <pred> x ... ) Conditionally enters a breakpoint. If <pred> is #f prints every x and enters a breakpoint. assoc assq assv (subroutine) (op x l) Returns the first pair in a list of pairs whose car component matches x. Assco uses equal? for comparison, assq uses eq? and assv eqv?. atan (basic subroutine) (atan n) returns the arcotangent of a number. atom? (basic subroutine) (atom? x) returns # if its arg is an atom (not a pair). autoload-from-file (subroutine) (autoload-from-file s l {e}) s is a string that names a file and l a list of variables. autoload-from-file loads the file s in the environment e the first time one of the variables contained in l is referenced. If e is omitted the file is loaded in the current environment. begin (basic subroutine) (begin <exp> ... ) Begin evaluates in sequence a list of expressions returning the value of the last <exp>. begin0 (subroutine) (begin0 <exp> ... ) Begin0 evaluates in sequence a list of expressions returning the value of the first <exp>. boolean? (defined in siod.scm) (boolean? x) Checks if its arg is #t or #f. c....r (defined in siod.scm as autoload-from-file) (c....r l) Performs a serie of car and cdr on a list. the .... can be any combination of the letters a and d, up to 4 characters, the a indicates a car and the d a cdr. call-with-current-continuation (defined in siod.scm) (call-with-current-continuation o) o is a procedure of one argument. call/cc calls this procedure passing it a procedure of one argument that represent the future of evaluation at the moment call/cc was evaluated. When this procedure is invoked its argument is returned as result of call/cc. In Siod continuations are valid only inside the procedure invoked by call/cc. call-with-input-file call-with-output-file (defined in siod.scm as autoload-from-file) (op s o) o is a procedure of one argument, it opens the file specified by the string s (the first opens an input file and the second an output file), and then invokes o passing it the file as argument. If o returns the file is closed. call/cc (defined in siod.scm) (call/cc o) Another name for call-with-current-continuation. car (basic subroutine) (car l) Returns the car component of a pair. case (subroutine) (case <exp1> (x <exp2> ...) ..... {(else <exp3> ...)}) Case evaluates <exp1> an then compares the result with the x's until the comparison is #t, or finds the keyword else. The comparison is perfomed using eqv? if the x is an atom and using memv? if is a pair. When the matching clause is found the exp's are evaluated in sequence and the value of the last exp returned as result of case. cdr (basic subroutine) (cdr l) Returns the cdr component of a pair. ceiling (basic subroutine) (ceiling n) Returns the smallest integer greater than or equal to n. char->integer (basic subroutine) (char->integer c) Return the ascii code corrispondent to the character c. char-ci<=? char-ci<? char-ci=? char-ci>=? char-ci>? (defined in siod.scm as autoload-from-file) (op c c) compares two characters in a case insensitive way. char-downcase char-upcase (subroutine) (op c) Forces a caracter to lowercase or uppercase. char<=? char<? char=? char>=? char>? (defined in siod.scm as autoload-from-file) (op c c) compares two characters. char? (basic subroutine) (char? x) Checks if its arg is a character. close-input-port close-output-port (subroutine) (op p) Close a port. closure? (subroutine) (closure? o) Checks if its arg is a closure (lambda named-lambda or fluid-lambda). complex (basic subroutine) (complex n) Forces a number to complex. complex? (basic subroutine) (complex? x) Checks if its arg is a complex number. cond (basic subroutine) (cond (<pred> <exp1> ... ) ..... {(else <exp2> ... )}) Evaluates the pred's until one evaluates to #t or it finds the keyword else, then the corrispondent exp's are evaluated in sequence and the value of the last exp returned. cons (basic subroutine) (cons x1 x2) Creates a new pair with x1 as car and x2 as cdr. cons-stream (defined in siod.scm as autoload-from-file) (cons-stream x1 x2) Creates a stream with x1 as head and x2 as tail. x2 isn't evaluated. copy (subroutine) (copy l) Creates a copy of an entire tree of pairs. cos (basic subroutine) (cos n) returns the cosine of a number. current-input-port current-output-port (defined in siod.scm as autoload-from-file) (op) Returns respectively the current input or output port. define (basic subroutine) (define y) (define y <exp>) (define spec <exp> ... ) spec: (y1 y2 ... {. y3}) | (spec y4 y5 ... {. y6}) The first form defines a variable in the current environment frame without initialize it. The second first evaluates the exp and then defines a variable in the current environment frame initializing it with the value returned by exp. The third is an abbreviated form to define procedures. (define (y1 y2 ...) <exp>) is equivalent to: (define y1 (lambda (y2 ...) <exp>) and (define (((y1) y2) y3) <exp>) is equivalent to: (define y1 (lambda () (lambda (y2) (lambda (y3) <exp>)))). delay (defined in siod.scm as autoload-from-file) (delay <exp>) Creates a delayed object. exp isn't evaluated. The object is memoized. delayed-object? (defined in siod.scm as autoload-from-file) (delayed-object? x) Checks if itsarg is a delayed object. delete! delq! (subroutine) (op x l) Destructively eliminates all the occurrences of x in l. The first uses equal? for comparison, the second eq?. denominator (basic subroutine) (denominator r) Returns the denominator of a rational number. display (basic subroutine) (display x {p}) Prints x to a port. Strings are not enclosed in ", symbols are not slashified, characters are not preceeded by #\. do (basic subroutine) (do ((y1 <exp1> <exp2>) .... ) (<pred> <exp3> ...) <exp4> ...) Provides an iteration capability. First extends the environment with all the y1 bound to the exp1, then evaluates pred, if it is #f evaluates exp4 and the other expressions and then evaluates all the exp2 and in a second time binds the result to the corrispondent y1. After this evaluates back pred and repeats the process until pred evaluates #t at this point evaluates exp3 and the other expressions returning the value of the last. dos-call (basic subroutine) (dos-call s) Passes a string to the DOS. empty-stream? (defined in siod.scm as autoload-from-file) (empty-stream? x) Checks if its arg is an empty-stream. environment-bindings (basic subroutine) (environment-bindings e) Returns the bindings of an environment. The bindings should not be modified. environment-parent (basic subroutine) (environment-parent e) Returns the parent of an environment. environment? (basic subroutine) (environment? x) Checks if its arg is an environment. eof-object? (basic subroutine) (eof-object? x) Checks if its arg is an eof marker. Is the only way to identify an eof. eq? (basic subroutine) (eq? x1 x2) Checks if x1 is identical to x2. equal? (basic subroutine) (equal? x1 x2) Checks if x1 is equivalent to x2 verifing eventually all the components of lists and vectors. eqv? (basic subroutine) (eqv? x1 x2) Checks if x1 is equivalent to x2 where x1 and x2 are non-pairs and non-vectors. error (basic subroutine) (error s x ...) Cause an error of message s and sets errobj to the list of x's. eval (basic subroutine) (eval <exp> {e}) Evaluates an expression in an environment. If e is omitted the current environment is used instead. even? (subroutine) (even? i) Checks if its arg is an even integer. exit (subroutine) (exit) Exits Siod. exp (basic subroutine) (exp n) returns e^n (e is the Eulero number). explode (defined in siod.scm as autoload-from-file) (explode i) (explode s) (explode y) Returns a list of one character symbols corresponding to the characters of the printed representation of its argument. expt (basic subroutine) (expt n1 n2) Returns n1 powered to n2. f (constant) f initialized to #f false (constant) false initialized to #f file-exists? (subroutine) (file-exists? s) Checks if exists a file named s. file-length (defined in siod.scm as autoload-from-file) (file-length s) Returns the length in bytes of the file named s. float (basic subroutine) (float n) Forces a number to float. float? (basic subroutine) (float? x) Checks if its arg is a float number. floor (basic subroutine) (floor n) Return the largest integer not greater than n. fluid (subroutine) (fluid y) Access a symbol in the fluid environment. fluid-bound? (subroutine) (fluid-bound? y) Returns #t if y is bound in the fluid environment. fluid-lambda (subroutine) (fluid-lambda ({y1 ...} {. y2}) <exp> ...) Returns a closures whose arguments will be bound in the fluid environment. If y2 is specified all the arguments passed to the closure that exceed the number of arguments needed are bound to y2 in a list. fluid-let (subroutine) (fluid-let ((y1 <exp1>) .... ) <exp2> ... ) evaluates all the <exp1>, binds the results to the correspondent y in the fluid environment and then evaluates all the exp2 returning the value of the last exp. flush-input (subroutine) (flush-input {p}) clears an input port's buffer. If p is not specified the current input port is used instead. for-each (subroutine) (for-each o l) o is a procedure of one argument. For-each applyes o to all the elements of l from left to rigth. force (defined in siod.scm as autoload-from-file) (force x) Forces the evaluation of a delayed object. If the object has been forced previously the previous result is returned. freesp (basic subroutine) (freesp) Returns the number of bytes available. freeze (defined in siod.scm as autoload-from-file) (freeze <exp>) Return a thunk. <exp> isn't evaluated and not memoized. gc (basic subroutine) (gc) Forces a garbage collection. gcd (basic subroutine) (gcd i ...) Returns the greatest common divisor of a list of integers. gensym (subroutine) (gensym) (gensym i) (gensym s) Generates a new uninterned symbol. The symbol is generated from a string and a counter if the arg is a string it replaces the current string, if it is an integer resets the counter. get-file-position (subroutine) (get-file-position p) Returns the value of the file pointer associated to p. getprop (subroutine) (getprop y1 y2) Looks for the property y2 in the proplist of y1. head (defined in siod.scm as autoload-from-file) (head stream) Returns the head component of a stream. if (basic subroutine) (if <pred> <exp1> <exp2>) Evaluates pred, if pred is #t evaluates exp1 else exp2. imaginary (basic subroutine) (imaginary m) (returns the imaginary part of a complex number. implode (defined in siod.scm as autoload-from-file) (implode l) l is a list composed by numbers, symbols or strings. Implode creates a symbol composed by the first character of the printed representation of strings and symbols or from the character of ASCII code correspondent to the integers contained in the list. input-port (fluid variable) (fluid input-port) Contains the default port used by the i/o routines. Must evaluate to a port or a fatal error occours. input-port? (subroutine) (input-port? x) Checks if its arg is an input port. inspect (basic subroutine) (inspect {e}) The default inspector invoked after an error or in a breakpoint. integer->char (basic subroutine) (integer->char i) Returns a character of ASCII code i. integer->string (subroutine) (integer->string i1 i2) Returns a string containing the written representation of i1 expressed in base i2. integer? (basic subroutine) (integer? x) Checks if its arg is an integer. lambda (basic subroutine) (lambda ({y1 ...} {. y2}) <exp> ...) Creates a new closure of arguments y's and body exp's. If y2 is specified all the arguments exeeding the number of args needed are linked together in a list and bound to y2. last-pair (subroutine) (last-pair l) Returns the last pair of a list. lcm (basic subroutine) (lcm i ...) Returns the lowest common multiplier of a list of integers. length (subroutine) (length l) Returns the length of a list. let (basic subroutine) (let ((y <exp1>) ..... ) <exp2> ... ) Evaluates all the exp's and then extends the environment binding each y with the result of the corresponding exp then evaluates all the exp2 and returns the value of the last exp. let* (subroutine) (let* ((y1 <exp1>) .... ) <exp2> ... ) Evaluates the first exp then extends the environment binding the result to the firs symbol, then evaluates in the extended environment the second symbol extending again the environment with the new binding, repeat thi for all the symbols and exp, then evaluates exp2 and the other exp returning yhe value of the last exp. letrec (subroutine) (letrec ((y1 <exp1>) .... ) <exp2> ... ) Extends the environment with all the ys, then evaluates all the exp in the extended environment and binds each y with the result of the corresponding exp, then evaluates exp2 and the other exp returning the value of the last exp. list (basic subroutine) (list x ...) Returns a list composed of all its arguments. list* (subroutine) (list x ...) Returns a dot-list (not nil terminated) composed of all its arguments. list->stream (defined in siod.scm as autoload-from-file) (list->stream l) Returns a stream containing the elements of l. list->string (subroutine) (list->string l) l is a list of characters. Retuns a string composed by the characters contained in l. list->vector (subroutine) (list->vector l) Returns a vector containing the same elements of l. list-ref (subroutine) (list-ref l n) Returns the n-th elements of l. list-tail (subroutine) (list-tail l n) Returns the n-th pair of a list. load (basic subroutine) (load s {e}) Loads a file named s evaluating its expression in e. If e is not specified the current environment is used insead. The optional environment is not standard. log (basic subroutine) (log n1 {n2}) returns the logarithm of n1 in base n2. If n2 is omitted the natural logarithm is returned. macro (basic subroutine) (macro y o) o is a procedure of one argument. Defines in the current environment y bound to a macro. When the macro is evaluated the current expression is passed to o and the result is evaluated instead. macro? (basic subroutine) (macro? y) Checks if its arg is a macro. make-complex (basic subroutine) (make-complex n1 n2) Creates a new complex number with n1 as real part and n2 as imaginary part. make-environment (defined in siod.scm) (make-environment <exp> ...) Creates a new environment, evaluates in it all the exp's and returns it. make-rational (basic subroutine) (make-rational n1 n2) Creates a new rational number with n1 as numerator and n2 as denominator. make-string (subroutine) (make-string i {c}) Creates a string composed by i occurrence of c or of blanks if c is omitted. make-vector (subroutine) (make-vector i {x}) Creates a vector composed by i occurrences of x or nil of x is omitted. map (basic subroutine) (map o l) o is a procedure of one argument. Map applyes o to every element of l returning a list of the results. mapc (subroutine) (mapc o l) The same as for-each. mapcar (subroutine) (mapcar o l) The same as map. max (basic subroutine) (max n ... ) Returns the greatest of a list of numbers. member memq memv (subroutine) (op x l) Returns the sublist beginning with the first occurrece of x in l. Member uses equal? for comparison, memq eq? memv eqv?. min (basic subroutine) (min n ... ) Return the smallest of a list of numbers. minus (subroutine) (minus n) returns the opposite of a number. modulo (basic subroutine) (modulo i1 i2) Returns the remainder of i1/i2 with the sign of i2. named-lambda (subroutine) (named-lambda (y1 {y2 ...} {. y3}) <exp> ...) Creates a new closure of arguments y2 ... and body exp's. When it's evaluated the procedure is bound to its name allowing recusion and relatively faster speed of execution. If y3 is specified all the arguments exeeding the number of args needed are linked together in a list and bound to y3. negative? (subroutine) (negative? n) Checks if its arg is a negative number. newline (defined in siod.scm as autoload-from-file) (newline {p}) Prints a newline on a port. If p is omitted the current output port is used instead. nil (constant) initialized to #f. not (subroutine) (not <exp>) Logically negates an expression. null? (basic subroutine) (null? x) Checks if its arg is the empty list. number->string (subroutine) (number->string n l) Return a string containing the written representation of n. l is a list specifing the format of n. Format allowed are: (int) express n as integer (heur) express n heuristically. number? (basic subroutine) (number? x) Checks if its arg is a number. numerator (basic subroutine) (numerator r) Returns the numerator part of a rational number. odd? (subroutine) (odd? i) Checks if its arg is an odd integer. open-binary-input-file open-binary-output-file (defined in siod.scm as autoload-from-file) (op s) Returns a port bound to a binary file of name s. If the file does not exists is created, if exists open-binary-output-file overwrites it. open-extend-file open-input-file open-output-file (defined in siod.scm as autoload-from-file) (op s) Returns a port bound to a file named s. If the file does not exists is created, if does not exists open-extend-file append the output to the end of file, open-output-file overwrites it. or (basic subroutine) (or <exp> ...) Performs a logical or between the exps. Evaluates the exp until they evaluates to #f and returns the value of the first exp that doesn't evaluates to #f or #f. output-port (fluid variable) (fluid output-port) Contains the default port used by the i/o routines. Must evaluate to a port or a fatal error occours. output-port? (subroutine) (output-port? x) Checks if its arg is an output port. page (defined in siod.scm as autoload-from-file) (page {p}) Prints a linefeed to a port if p is omitted the current output port is used instead. pair? (subroutine) (pair? x) Checks if its arg is a pair. pi (constant) The ratio of a circumference to its diameter. port? (basic subroutine) (port? x) Checks if its arg is a port. positive? (subroutine) (positive? n) Returns #t if its arg is greater than or equal to 0. prin1 (subroutine) (prin1 x {p}) The same as write. princ (subroutine) (princ x {p}) The same as display. print (basic subroutine) (print x {p}) Prints x to a port on a new line using write. print-length (subroutine) (print-length x1 {x2}) Calculates the number of characters needed to print x1 using display. If x2 is specified and evaluates to #t uses write instead. x2 is not standard. proc? (basic subroutine) (procedure? x) Checks if its arg is a subroutine, a special form or a closure. procedure-environment (subroutine) (procedure-environment o) Returns the environment where o was defined. procedure? (subroutine) (procedure? x) Checks if its arg is a subroutine or a special form. proplist (subroutine) (proplist y) Returns the property-list associated to y. putprop (subroutine) (putprop y1 x y2) Adds the prop y2 to the proplist of y1 with the value of x. quasiquote (subroutine) (quasiquote x) `x Returns its arg unevaluated eventually evaluating the special forms , ,@ ,. unquote unquote-splicing contained in it. (unquote x) or ,x cause the x to be evaluated and inserted in the list instead of it. The arg of (unquote-splicing l) or ,@l must be a list and cause the elements of the list replace it without parenthesis. With ,.l the splicing is destructive. Unquoting happens only at the first level of quasiquoting. quote (basic subroutine) (quote x) 'x Returns its argument unevaluated. quotient (basic subroutine) (quotient i1 i2) Returns the quotient of i1/i2. random (basic subroutine) (random i) Returns a random number between 0 and i-1. randomize (basic subroutine) (randomize i) Start a new series of random numbers. If i is 0 the timer is used as seed. rational (basic subroutine) (rational n) Forces a number to rational. rational? (basic subroutine) (rational? x) Checks if its arg is a rational number. read (basic subroutine) (read {p}) Reads a scheme expression from a port. If p is omitted the current port is used instead. read-char (subroutine) (read-char {p}) Reads a character from a port. If p is omitted the current port is used instead. read-line (subroutine) (read-line {p}) Returns a string containing a line read from a port. If p is omitted the current port is used instead. real (basic subroutine) (real m) Returns the real part of a complex number. real? (subroutine) (real? x) Checks if its arg is a real number (integer rational or float). rec (defined in siod.scm) (rec y <exp>) Extend the environment binding y to exp and then evaluates exp and return it value. remainder (basic subroutine) (remainder i1 i2) Returns the remainder of i1/i2 with the sign of i1. remprop (subroutine) (remprop y1 y2) Removes The property y2 from the proplist of y1. reset (subroutine) (reset) aborts evaluation restarting the current scheme-top-level loop. reset-scheme-top-level (subroutine) (reset-scheme-top-level) Binds the fluid variable scheme-top-level to the default read-eval-print loop without starting it. reverse (basic subroutine) (reverse l) Returns a list containing the same elements of l in reverse order. reverse! (subroutine) (reverse l) Destructively returns a list containing the same elements of l in reverse order. round (basic subroutine) (round n) Returns the integer closest to n. runtime (subroutine) (runtime) Returns the time of day expressed in milliseconds. scheme-reset (subroutine) (scheme-reset) Resets the fluid variable scheme-top-level to its default value and the fluid variables input-port output-port to the value of standard-input standard-output respectively. Then restarts the execution. Resets also the inspector to the default inspector and *error* to the default error handler. scheme-top-level (fluid variable) (fluid scheme-top-level) contains the corrent top-level read-eval-print loop. Can be rebound by the user. If the procedure returns the system invokes it again. sequence (subroutine) (sequence <exp> ...) The same as begin. set! (basic subroutine) (set! y x) (set! (fluid y) x) (set! (vector-ref v i) x) (set! (access y {e}) x) The first form sets the binding of the symbol y in the current environment to x. The second sets the binding of the symbol y in the fluid environment to x. The third sets the i-th element of the vector v to x. The fourth sets the binding of the symbol y in the environment e to x. If e is omitted the current environment is used instead. set-car! (basic subroutine) (set-car! l x) sets the car component of the pair l to x. set-cdr! (basic subroutine) (set-cdr! l x) sets the cdr component of the pair l to x. set-file-position! (subroutine) (set-file-position! p i1 i2) Positions the file pointer inside the file associated to p if i2 is 0 sets the file position to i1 bytes from the beginning of the file. if i2 is 1 sets the file position to i1 bytes from the current position of the file. if i2 is 2 sets the file position to i1 bytes from the end of the file. set-fluid! (subroutine) (set-fluid! y x) Sets the binding of y in the fluid environment to x. sin (basic subroutine) (sin n) Returns the sin of a number. sort! (defined in siod.scm as autoload-from-file) (sort! l) (sort! v) Destructively sorts a list or a vector. It uses quicksort for vectors and merge-sort for lists. sqrt (basic subroutine) (sqrt n) Returns the square root of a number. standard-input (variable) standard-input Contains the standard input. Is initialized to the console. Must evaluate to a port or a fatal error occours. standard-output (variable) standard-output Contains the standard output. Is initialized to the console. Must evaluate to a port or a fatal error occours. stream->list (defined in siod.scm as autoload-from-file) (stream->list stream) Converts a finite stream to a list. stream? (defined in siod.scm as autoload-from-file) (stream? x) Checks if its arg is a stream. string->list (subroutine) (string->list s) returns a list composed of the characters contained in s. string->number (subroutine) (string->number s y1 y2) Converts a string to a number. y1 represent the exactness but it is not implemented on siod and then is ininfluent. y2 is the radix and can be: 'b indicates that s represents a binary number 'd indicates that s represents a decimal number 'o indicates that s represents an octal number 'x indicates that s represents an hexadecimal number string->symbol (subroutine) (string->symbol s) Returns a symbol of printed representation correspondent to the string s. string->uninterned-symbol (subroutine) (string->uninterned-symbol s) Returns an uninterned symbol of printed representation correspondent to the string s. string-CI<? string-CI=? (defined in siod.scm as autoload-from-file) (op s1 s2) Compares two string in a case insensitive way. string-append (basic subroutine) (string-append s ...) Returs the string obtained concatenating all its arg. string-copy (subroutine) (string-copy s) Returns a new string identical to s. string-fill! (subroutine) (string-fill! s {c}) Replaces all the caracters in s with the character c. If c is omitted a blank is used. string-length (basic subroutine) (string-length s) Returns the length of the string s. string-null? (defined in siod.scm as autoload-from-file) (string-null? x) Checks if its arg is an empty string. string-ref (basic subroutine) (string-ref s i) Returns the i-th character of the string s. The first character has index 0. string-set! (basic subroutine) (string-set! s i c) Replaces the i-th character of the string s with the character c. The first character has index 0. string<=? string<? string=? string>=? string>? (defined in siod.scm as autoload-from-file) (op s1 s2) Compares two strings. string? (basic subroutine) (string? x) Checks if its arg is a string. sub1 (subroutine) (sub1 n) Subtracts 1 from its arg. substring (basic subroutine) (substring s i1 i2) Returns a string that contains the part of the string s between i1 and i2-1. substring-CI<? substring-CI=? (defined in siod.scm as autoload-from-file) (op s1 i1 i2 s2 i3 i4) Compares the substring of s1 between i1 and i2-1 and the substring of s2 between i3 and i4-1 in a character insensitive way. substring-fill! (defined in siod.scm as autoload-from-file) (substring-fill! s i1 i2 c) Replaces all the characters in the string s between i1 and i2-1 with the character c. substring-find-next-char-in-set substring-find-previous-char-in-set (op s1 i1 i2 c) (op s1 i1 i2 s2) Searches, in the substring of s1 between i1 and i2, the first occurrence of the char c or of one of the characters of the string s2. The first procedure searches starting from i1 to i2 and the second from i2 to i1. substring-move-left! substring-move-right! (defined in siod.scm as autoload-from-file) (op s1 i1 i2 s2 i3) Copies the substring of s1 between i1 and i2-1 to s2 starting at position i3. The first starts copying from the left to the rigth and the second from the rigth to the left. If s1 and s2 are different strings there is no difference between the two procedures but if the string is the same and the indexes are overlapping the behaviour can be different. substring<? substring=? (defined in siod.scm as autoload-from-file) (op s1 i1 i2 s2 i3 i4) Compares the substring of s1 between i1 and i2-1 and the substring of s2 between i3 and i4-1. symbol->ascii (subroutine) (symbol->ascii y) Returns the ascii code correspondent to the first character in the printed representation of the symbol. symbol->string (subroutine) (symbol->string y) Returns a string containing the written representation of the symbol y. symbol? (basic subroutine) (symbol? x) Checks if its arg is a symbol. t (constant) t initialized to the value #t true (constant) true initialized to the value #t tail (defined in siod.scm as autoload-from-file) (tail stream) Forces the evaluation and returns the tail component of a stream. This component is memoized. tan (basic subroutine) (tan n) returns the tangent of a number. thaw (defined in siod.scm as autoload-from-file) (thaw o) Forces the evaluation of a thunk. Not memoized. the-empty-stream (defined in siod.scm as autoload-from-file) the-empty-stream is a stream representing the end-of-stream tag. the-environment (basic subroutine) (the-environment) Returns the current environment. transcript-off (subroutine) (transcript-off) Terminates the recording of all the console i/o to the transcript file and closes it. Non standard feature: returns #f if the transcript mode is already off otherwise #t. transcript-on (subroutine) (transcript-on s) Opens a file named s and starts recording all the console i/o to that file. truncate (basic subroutine) (truncate n) Returns the integer component of a number. unbound? (subroutine) (unbound? y {e}) Returns #t if the symbol y is not bound in the environment e. If e is omitted the current environment is used instead. unquote (subroutine) (unquote <exp>) ,<exp> Is valid only inside a quasiquote expression. Cause the exp to be evaluated and the result is inserted in the quasiquote expression instead of the unquote expression. unquote-splicing (subroutine) (unquote-splicing <exp>) ,@<exp> Is valid only inside a quasiquote expression. Cause the exp to be evaluated (it must evaluae to a list) and the result is inserted in the quasiquote expression instead of the unquote-splicing expression stripping away the parenthesis. user-global-environment (constant) user-global-environment To this variable is bound the global environment whose bindings cannot be examinated. user-initial-environment (constant) user-initial-environment In this environment are evaluated and defined the user procedures and commands. vector (basic subroutine) (vector x ...) Returns a vector containing its args. vector->list (subroutine) (vector->list v) Returns a list containing the same elements of the vector. vector-fill! (subroutine) (vector-fill! v x) Replaces each element of v with the value of x. vector-length (basic subroutine) (vector-length v) Returns the length of v. vector-ref (basic subroutine) (vector-ref v i) Returns the i-th element of a vector. The first element of the vector has index 0. vector-set! (basic subroutine) (vector-set! v i x) Sets the i-th element of a vector to the value of x. The first element of the vector has index 0. vector? (basic subroutine) (vector? x) Checks if its arg is a vector. when (subroutine) (when <pred> <exp> ...) Evaluates pred if its value is #t evaluates all the expression. with-input-from-file with-output-to-file (defined in siod.scm as autoload-from-file) (op s o) o is a thunk a procedure of no arguments. These procedures opens a file named s, replaces the current input or output port with this file and then invokes o. The file s is always closed and the current port restored. In Siod if you exit from o with an escape mechanism (call/cc or *thaw) this happens only at the first reset or error. write (subroutine) (write x {p}) Writes an expression to a port. The expression is written in such a way that if re-read into scheme using read will produce the same object. Strings are enclosed in " and eventually slashed, symbols are slashed if necesary, characters are preceeded by a #\, objects like ports, environment, procedures, closures, etc that can not be re-read into scheme prints a #<name> where name is the name of the object. To convey some information to the user write prints also the type of procedures and the number of arguments needed to a closure. Types of procedures are: 0 a procedure with 0 args 1 a procedure with 1 args 2 a procedure with 2 args 3 a procedure with 3 args 4 a procedure with more than 3 5 a special form 6 a special form write-char (subroutine) (write-char c {p}) writes a character to a port. If p is omitted the current output port is used. writeln (basic subroutine) (writeln x ... ) writes a list of objects to the current output port using display. zero? (subroutine) (zero? n) checks if n is zero. LANGUAGE EXTENSIONS, SYSTEM AND USER PACKAGES (non standard) *cargs* (variable) *cargs* Inside a breakpoint it evaluates to the current stack frame. *catch (subroutine) (*catch x <exp> ...) Sets a jump point of tag x, evaluates each exp and then removes the jump point. When a *throw jumps to the jump point removes all the jump points that have been set after it. *cenv* (variable) *cenv* Inside a breakpoint it evaluates to the environment in effect when the breakpoint was entered. *error* (basic subroutine) (*error*) This is the default error handler. It flushes all the output port, checks the current input or output ports and eventually replaces them with the standard ports, prints the error message and if the variable sym_debug_mode is #t invokes the inspector. When an error occours Siod sets the variables errobj *lasterr* *cenv* *cargs* and invokes *error*, when it returns siod sets the variables *cenv* and *cargs* to nil (they can point to very large an often useless structures and the gc cannot deallocate them until something points to them) and performs a reset. *lasterr* (variable) *lasterr* The last error message is bound by the system to this variable. *on-reset* (variable) *on-reset* This variable is evaluated each time a reset is performed in the file siod.scm is initialized to the reset-handler contained in *on-reset-env*. *on-reset-env* (constant) *on-reset-env* Contains a stack of thunks, procedures of 0 args that will be evaluated at the first reset. When a reset occours the first thunk is removed from the stack and then evaluated and so on until the stack is empty. Can be used by the user to intercept errors and resets. Each thunk is evaluated once. *throw (subroutine) (*throw x1 x2) Jumps to the jump point marked by the tag x1, the value x2 is returned by the corresponding *catch. All the jump points set after this are removed. *tracer* (defined in siod.scm as autoload-from-file) (*tracer* s e) Used by the trace procedure. 1st 2nd 3rd 4th (defined in siod.scm as autoload-from-file) (op l) The same as car cadr caddr cadddr respectively. bkpt (subroutine) (bkpt s x ...) Enters a breakpoint, sets the variables *cenv* *cargs* to the current stack frame and environment sets the errobj to the x's, prints s and all the x and invokes the standard inspector. break (defined in siod.scm as autoload-from-file) (break o {s}) This is a debugging utility. o is a procedure, break modify its code so that every time the procedure is entered the optional string s is printed and a breakpoint entered. If the breakpoint ever returns the evaluation restarts executing the body of the procedure. The break point is entered after the environment has been extended with the arguments. call-on-reset (defined in siod.scm) (call-on-reset o) Adds the thunk o to the stack of thunks that will be executed at the next reset. char-cmp (basic subroutine) (char-cmp c1 c2) Compares two characters. Returns 0 if c1=c2, a negative value if c1<c2, a positive value if c1>c2. char-digit? char-lower-case? char-upper-case? (defined in siod.scm as autoload-from-file) (op c) Checks if its arg is a character representing a digit, a lowercase letter or an uppercase letter respectively. close-port (basic subroutine) (close-port p) Closes a port. compose (defined in siod.scm) (compose o1 o2) Returns a procedure that is the equivalent of (o2 (o1 ..)). cxr (subroutine) (cxr s l) Performs a series of car and cdr on the list l as specified by the string s, read from rigth to left. Every a corresponds to a car and every d to a cdr. cycle (defined in siod.scm) (cycle <exp>) Evaluates indefinitely <exp>. flush-port (subroutine) (flush-port p) Performs a fflush and a clearerr on the file pointer associated to the port. for (defined in siod.scm) (for y <exp1> <exp2> <pred> <exp3> ...) Extends the environment binding the symbol y to the value of exp1 then evaluates the pred if its value is #t returns otherwise evaluates the other exps and then evaluates exp2, binds the symbol y to its value and evaluates back the pred. gc-status (subroutine) (gc-status) Prints some informations on the system variables, the number of cons available, the number of buckets of the symbol table used and calculates the loading factor of the table. nth (defined in siod.scm) (nth l i) The same as list-ref. open-port (basic subroutine) (open-port s1 s2 i) Return a port associated with the file named s1. s2 represents the open mode following the C-language convensions: "r" open a file in read mode, "w" open a file in write mode, "a" open a file in append mode, if a "+" is specified in the string the file is opened in read/write mode and if a "b" is specified opens a binary file. If a file is opened in read/write mode, following the C-language convensions between a read and a write operation a fflush (flush-port in siod) should be performed. i specifies the bufferization of the file, if its value is positive a full bufferization is used with a 512 bytes buffer, if its value is negative a line bufferization is used and if is 0 the file is unbuffered. procedure-code (subroutine) (procedure-code o) Returns the procedure code of o. The procedure code is a pair whose car is the arg-list and the cdr the body. quit (basic subroutine) (quit) Exits siod. repeat (defined in siod.scm) (repeat <exp> <pred>) Evaluates the exp and then the pred if its value is #t returns otherwise evaluates back th exp. set-procedure-code! (subroutine) (set-procedure-code! o l) Replaces the procedure code of o with l. Must be used carefully. The procedure code is a pair whose car is the arg-list and the cdr the body. siod-debug-mode (variable) siod-debug-mode If set to #t the inspector is invoked after each error. siod-gc-mode (variable) siod-gc-mode If set to #t before and after each gc a message is printed. siod-repl-mode (variable) siod-repl-mode If set to #t after the evaluation of each command some informations on the timing and the memory usage are printed. stream-append (defined in siod.scm as autoload-from-file) (stream-append stream1 stream2) Returns a stream obtained concatenating stream1 and stream2. stream-filter (defined in siod.scm as autoload-from-file) (stream-filter <pred> stream) Applies the pred to all the elements of a finite stream and returns a stream of that elements for which the result of the pred was #t. stream-for-each (defined in siod.scm as autoload-from-file) (stream-map o stream) Applies the procedure o to all the elements of a finite stream. stream-map (defined in siod.scm as autoload-from-file) (stream-map o stream) Applies the procedure o to all the elements of a finite stream returning a stream of the results. stream-nth (defined in siod.scm as autoload-from-file) (stream-nth i stream) The same as stream-ref. stream-ref (defined in siod.scm as autoload-from-file) (stream-ref i stream) Returns the i-th component of a stream. string-cmp (basic subroutine) (string-cmp s1 s2) Compares two strings. The result is 0 if s1=s2, is positive if s1>s2, negative if s1<s2. string-cmp-ci (subroutine) (string-cmp-ci s1 s2) Compares two strings in a case insensitive way. The result is 0 if s1=s2, is positive if s1>s2, negative if s1<s2. time-of-day (defined in siod.scm) (time-of-day) The same as runtime. trace (defined in siod.scm as autoload-from-file) (trace o {s}) This is a debugging utility o is a procedure, trace modify its code so that every time the procedure is entered the optional string s or the string "entering procedure " is printed and the contents of the last environment frame (the one that contains the argument bindings) is listed. Then the execution restarts. unbreak (defined in siod.scm as autoload-from-file) (unbreak o) Removes the break informations from o. uncall-on-reset (defined in siod.scm) (uncall-on-reset o) Removes the thunk o from the stack of thunks that will be executed at the next reset using delq!. untrace (defined in siod.scm as autoload-from-file) (untrace o) Removes the break informations from o. vector-append (defined in siod.scm as autoload-from-file) (vector-append v1 v2) Returns a vector containing all the elements of v1 and v2. vector-copy (defined in siod.scm as autoload-from-file) (vector-copy v) Returns a vector containing all the elements of v. vector-for-each (defined in siod.scm as autoload-from-file) (vector-for-each v o) Applies the procedure o to all the elements of v. vector-map (defined in siod.scm as autoload-from-file) (vector-map v o) Applies the procedure o to all the elements of v and returns avector of the results. vector-reverse (defined in siod.scm as autoload-from-file) (vector-reverse v) Returns a vector containing the same elements as v but in reverse order. vector-reverse! (defined in siod.scm as autoload-from-file) (vector-reverse! v) Destructively reverse the order of the elements of v. while (subroutine) (while <pred> <exp> ...) Evaluates pred and if its alue is #t evaluates the exps and then evaluates back the pred.