Base Library

The (scheme base) library exports many of the procedures and syntax bindings that are traditionally associated with Scheme.

For more information see the R7RS Scheme Specification.

abs

(abs num)

Return the absolute value of num.

and

Syntax

(and {test1} ...)

Semantics: The {test} expressions are evaluated from left to right, and if any expression evaluates to #f, then #f is returned. Any remaining expressions are not evaluated. If all the expressions evaluate to true values, the values of the last expression are returned. If there are no expressions, then #t is returned.

(and (= 2 2) (> 2 1)) => #t
(and (= 2 2) (< 2 1)) => #f
(and 1 2 '(f g)) => (f g)
(and) => #t

any

(any pred lst)

Return #t if predicate function pred is true for any value of lst. Otherwise #f is returned.

append

(append list ...)

The last argument, if there is one, can be of any type.

Returns a list consisting of the elements of the first list followed by the elements of the other lists. If there are no arguments, the empty list is returned. If there is exactly one argument, it is returned. Otherwise the resulting list is always newly allocated, except that it shares structure with the last argument. An improper list results if the last argument is not a proper list.

(append '(x) '(y)) => (x y)
(append '(a) '(b c d)) => (a b c d)
(append '(a (b)) '((c))) => (a (b) (c))
(append '(a b) '(c . d)) => (a b c . d)
(append '() 'a) => a

assoc

(assoc obj alist)

(assoc obj alist compare)

It is an error if alist (for “association list”) is not a list of pairs.

This procedure finds the first pair in alist whose car field is obj, and returns that pair. If no pair in alist has obj as its car, then #f (not the empty list) is returned.

assoc uses compare to compare obj with the car fields of the pairs in alist if given and equal? otherwise.

assq

(assq obj alist)

The assq procedure is the same as assoc except it uses eq? to compare obj with the car fields of the pairs in alist.

assv

(assv obj alist)

The assv procedure is the same as assoc except it uses eqv? to compare obj with the car fields of the pairs in alist.

begin

Syntax

(begin {expression or definition} ...)

This form of begin can appear as part of a {body}, or at the outermost level of a {program}, or at the REPL, or directly nested in a begin that is itself of this form. It causes the contained expressions and definitions to be evaluated exactly as if the enclosing begin construct were not present.

Rationale: This form is commonly used in the output of macros which need to generate multiple definitions and splice them into the context in which they are expanded.

(begin {expression1} {expression2} ...)

This form of begin can be used as an ordinary expression. The {expression}’s are evaluated sequentially from left to right, and the values of the last {expression} are returned. This expression type is used to sequence side effects such as assignments or input and output.

(define x 0)

(and (= x 0)
     (begin (set! x 5)
            (+ x 1))) => 6

(begin (display "4 plus 1 equals ")
       (display (+ 4 1))) => unspecified and prints 4 plus 1 equals 5

boolean=?

(boolean=? b1 b2 ...)

Returns #t if all the arguments are booleans and all are #t or all are #f.

bytevector-copy

(bytevector-copy bytevector)

(bytevector-copy bytevector start)

(bytevector-copy bytevector start end)

Returns a newly allocated bytevector containing the bytes in bytevector between start and end.

(define a #u8(1 2 3 4 5))
(bytevector-copy a 2 4)) => #u8(3 4)

bytevector-copy!

(bytevector-copy! to at from)

(bytevector-copy! to at from start)

(bytevector-copy! to at from start end)

Copies the bytes of bytevector from between start and end to bytevector to, starting at at.

(define a (bytevector 1 2 3 4 5))
(define b (bytevector 10 20 30 40 50))
(bytevector-copy! b 1 a 0 2)
b => #u8(10 1 2 40 50)

call-with-current-continuation

(call-with-current-continuation proc)

call-with-port

(call-with-port port proc)

It is an error if proc does not accept one argument.

The call-with-port procedure calls proc with port as an argument. If proc returns, then the port is closed automatically and the values yielded by the proc are returned.

call-with-values

(call-with-values producer consumer)

Calls its producer argument with no arguments and a continuation that, when passed some values, calls the consumer procedure with those values as arguments. The continuation for the call to consumer is the continuation of the call to call-with-values.

(call-with-values (lambda () (values 4 5))
(lambda (a b) b))
=> 5
(call-with-values * -) => -1

call/cc

(call/cc proc)

An abbreviation for call-with-current-continuation.

case

Syntax

(case {key} {clause1} {clause2} ...)

Syntax: {Key} can be any expression. Each {clause} has the form

(({datum1} ...) {expression1} {expression2} ...),

where each {datum} is an external representation of some object. It is an error if any of the {datum}’s are the same anywhere in the expression. Alternatively, a {clause} can be of the form

((hdatum1} ...) => {expression})

The last {clause} can be an “else clause,” which has one of the forms

(else {expression1} {expression2} . . . )

or

(else => {expression}).

Semantics: A case expression is evaluated as follows. {Key} is evaluated and its result is compared against each {datum}. If the result of evaluating {key} is the same to a {datum}, then the expressions in the corresponding {clause} are evaluated in order and the results of the last expression in the {clause} are returned as the results of the case expression.

If the result of evaluating {key} is different from every {datum}, then if there is an else clause, its expressions are evaluated and the results of the last are the results of the case expression; otherwise the result of the case expression is unspecified.

If the selected {clause} or else clause uses the => alternate form, then the {expression} is evaluated. It is an error if its value is not a procedure accepting one argument. This procedure is then called on the value of the {key} and the values returned by this procedure are returned by the case expression.

(case (* 2 3)
  ((2 3 5 7) 'prime)
  ((1 4 6 8 9) 'composite)) => composite
(case (car '(c d))
  ((a) 'a)
  ((b) 'b)) => unspecified
(case (car '(c d))
  ((a e i o u) 'vowel)
  ((w y) 'semivowel)
  (else => (lambda (x) x))) => c

ceiling

(ceiling z)

Returns the smallest integer not smaller than z.

char<=?

(char<=? c1 c2 c3 ...)

Return #t if the results of passing the arguments to char->integer are monotonically increasing or equal.

char<?

(char<?  c1 c2 c3 ...)

Return #t if the results of passing the arguments to char->integer are respectively equal, monotonically increasing.

char=?

(char=?  c1 c2 c3 ...)

Return #t if the results of passing the arguments to char->integer are equal.

char>=?

(char>=? c1 c2 c3 ...)

Return #t if the results of passing the arguments to char->integer are monotonically decreasing or equal.

char>?

(char>?  c1 c2 c3 ...)

Return #t if the results of passing the arguments to char->integer are monotonically decreasing.

complex?

(complex? obj)

Return #t if obj is a complex number, #f otherwise.

cond

Syntax

(cond {clause1} {clause2} ...)
else
=>

Syntax: {Clauses} take one of two forms, either

({test} {expression1} ...)

where {test} is any expression, or

({test} => {expression})

The last {clause} can be an “else clause,” which has the form

(else {expression1} {expression2} ...)

Semantics: A cond expression is evaluated by evaluating the {test} expressions of successive {clause}’s in order until one of them evaluates to a true value. When a {test} evaluates to a true value, the remaining {expression}’s in its {clause} are evaluated in order, and the results of the last {expression} in the {clause} are returned as the results of the entire cond expression.

If the selected {clause} contains only the {test} and no {expression}’s, then the value of the {test} is returned as the result. If the selected {clause} uses the => alternate form, then the {expression} is evaluated. It is an error if its value is not a procedure that accepts one argument. This procedure is then called on the value of the {test} and the values returned by this procedure are returned by the cond expression.

If all {test}’s evaluate to #f, and there is no else clause, then the result of the conditional expression is unspecified; if there is an else clause, then its {expression}’s are evaluated in order, and the values of the last one are returned.

(cond ((> 3 2) 'greater)
      ((< 3 2) 'less)) => greater
(cond ((> 3 3) 'greater)
      ((< 3 3) 'less)
      (else 'equal)) => equal
(cond ((assv 'b '((a 1) (b 2))) => cadr)
      (else #f)) => 2

cond-expand

Syntax

(cond-expand {ce-clause2} {ce-clause2} ...)

Syntax: The cond-expand expression type provides a way to statically expand different expressions depending on the implementation. A {ce-clause} takes the following form:

({feature requirement} {expression} ...)

The last clause can be an “else clause,” which has the form

(else {expression} ...)

A {feature requirement} takes one of the following forms:

Semantics: Each Scheme implementation maintains a list of feature identifiers which are present, as well as a list of libraries which can be imported. The value of a {feature requirement} is determined by replacing each {feature identifier} and (library {library name}) on the implementation’s lists with #t, and all other feature identifiers and library names with #f, then evaluating the resulting expression as a Scheme boolean expression under the normal interpretation of and, or, and not.

A cond-expand is then expanded by evaluating the {feature requirement}’s of successive {ce-clause}’s in order until one of them returns #t. When a true clause is found, the corresponding {expression}’s are expanded to a begin, and the remaining clauses are ignored. If none of the {feature requirement}’s evaluate to #t, then if there is an else clause, its {expression}’s are included. Otherwise, the behavior of the cond-expand is unspecified. Unlike cond, cond-expand does not depend on the value of any variables.

current-error-port

(current-error-port)

Returns the current error port (an output port).

current-input-port

(current-input-port)

Return the current input port.

current-output-port

(current-output-port)

Return the current output port.

define-record-type

Syntax

(define-record-type {name}

  {constructor} {pred} {field} ...)

Create a new record type.

Record-type definitions are used to introduce new data types, called record types. Like other definitions, they can appear either at the outermost level or in a body. The values of a record type are called records and are aggregations of zero or more fields, each of which holds a single location. A predicate, a constructor, and field accessors and mutators are defined for each record type.

denominator

(denominator n)

Return the denominator of n.

do

Syntax

(do (({variable1} {init1} {step1})

     ...)

({test} {expression} ...)

{command} ...)

dynamic-wind

(dynamic-wind before thunk after)

Calls thunk without arguments, returning the result(s) of this call.

before is called whenever execution enters the dynamic extent of the call to thunk and after is called whenever it exits that dynamic extent.

eof-object

(eof-object)

Return the end of file (EOF) object.

error

(error message obj ...)

Raise an error with message message and one or more associated objects obj.

even?

(even? num)

Return #t if num is even and #f if it is not. It is an error if num is not a number.

every

(every pred lst)

Return #t if predicate function pred is true for every value of lst. Otherwise #f is returned.

exact

(exact num)

Return an exact representation of number num.

exact-integer?

(exact-integer? num)

Returns #t if num is both exact and an integer; otherwise returns #f.

exact?

(exact? num)

Return #t if num is exact.

expt

(expt z1 z2)

features

(features)

Return a list of feature identifiers which cond-expand treats as true.

floor

(floor z)

Return an integer not larger than z.

floor-quotient

(floor-quotient n m)

Returns the integer quotient of dividing n by m.

floor-remainder

(floor-remainder n m)

Returns the integer remainder of dividing n by m.

floor/

(floor/ n m)

Return integer quotient and remainder of dividing n by m.

flush-output-port

(flush-output-port)

(flush-output-port port)

Flushes any buffered output from the buffer of output-port to the underlying file or device and returns an unspecified value.

foldl

(foldl func accum lst)

Perform a left fold.

foldr

(foldr func end lst)

for-each

(for-each proc list1 list2 ...)

It is an error if proc does not accept as many arguments as there are lists.

The arguments to for-each are like the arguments to map, but for-each calls proc for its side effects rather than for its values. Unlike map, for-each is guaranteed to call proc on the elements of the lists in order from the first element(s) to the last, and the value returned by for-each is unspecified. If more than one list is given and not all lists have the same length, for-each terminates when the shortest list runs out. The lists can be circular, but it is an error if all of them are circular.

(let ((v (make-vector 5)))
  (for-each (lambda (i)
              (vector-set! v i (* i i)))
            ’(0 1 2 3 4))
  v) => #(0 1 4 9 16)

gcd

(gcd n1 ...)

Return the greatest commong divisor of the arguments.

get-output-bytevector

(get-output-bytevector port)

Returns a bytevector consisting of the bytes that have been output to the port so far in the order they were output.

get-output-string

(get-output-string port)

Returns a string consisting of the characters that have been output to the port so far in the order they were output. If the result string is modified, the effect is unspecified.

(parameterize
  ((current-output-port
   (open-output-string)))
  (display "piece")
  (display " by piece ")
  (display "by piece.")
  (newline)
  (get-output-string (current-output-port)))

  => "piece by piece by piece.\n"

guard

Syntax

(guard ({variable}

        {cond clause1} {cond clause2} ...)

  {body})

inexact

(inexact z)

Return z as an inexact number.

inexact?

(inexact? num)

Return #t if num is inexact and #f otherwise.

input-port-open?

(input-port-open? port)

Return #t if the given input port is open and #f otherwise.

input-port?

(input-port? port)

Return #t if port is an input port and #f otherwise.

lcm

(lcm n1 ...)

Return the least common multiple of the arguments.

let

Syntax

(let {bindings} {body})

{bindings} has the form:

(({variable1} {init1}) ...)

where each {init} is an expression, and {body} is a sequence of zero or more definitions followed by a sequence of one or more expressions. It is an error for a {variable} to appear more than once in the list of variables being bound.

Semantics: The {init}’s are evaluated in the current environment (in some unspecified order), the {variable}’s are bound to fresh locations holding the results, the {body} is evaluated in the extended environment, and the values of the last expression of {body} are returned. Each binding of a {variable} has {body} as its region.

(let ((x 2) (y 3))
  (* x y)) => 6

(let ((x 2) (y 3))
  (let ((x 7)
    (z (+ x y)))
  (* z x))) => 35

let*

Syntax

(let* {bindings} {body})

{bindings} has the form:

(({variable1} {init1}) ...)

where each {init} is an expression, and {body} is a sequence of zero or more definitions followed by a sequence of one or more expressions. It is an error for a {variable} to appear more than once in the list of variables being bound.

Semantics: The let* binding construct is similar to let, but the bindings are performed sequentially from left to right, and the region of a binding indicated by ({variable} {init}) is that part of the let* expression to the right of the binding. Thus the second binding is done in an environment in which the first binding is visible, and so on.

The {variable}’s need not be distinct.

(let ((x 2) (y 3))
    (let* ((x 7)
           (z (+ x y)))
      (* z x))) => 70

let*-values

Syntax

(let*-values {mv binding spec} {body})

let-values

Syntax

(let-values {mv binding spec} {body})

letrec

Syntax

(letrec {bindings} {body})

{bindings} has the form:

(({variable1} {init1}) ...)

where each {init} is an expression, and {body} is a sequence of zero or more definitions followed by a sequence of one or more expressions. It is an error for a {variable} to appear more than once in the list of variables being bound.

Semantics: The {variable}’s are bound to fresh locations holding unspecified values, the {init}’s are evaluated in the resulting environment (in some unspecified order), each {variable} is assigned to the result of the corresponding {init}, the {body} is evaluated in the resulting environment, and the values of the last expression in {body} are returned.

Each binding of a {variable} has the entire letrec expression as its region, making it possible to define mutually recursive procedures.

(letrec ((even?
          (lambda (n)
            (if (zero? n)
                #t
                (odd? (- n 1)))))
         (odd?
          (lambda (n)
            (if (zero? n)
                #f
                (even? (- n 1))))))
  (even? 88))
      => #t

One restriction on letrec is very important: if it is not possible to evaluate each {init} without assigning or referring to the value of any {variable}, it is an error. The restriction is necessary because letrec is defined in terms of a procedure call where a lambda expression binds the {variable}’s to the values of the {init}’s. In the most common uses of letrec, all the {init}’s are lambda expressions and the restriction is satisfied automatically.

letrec*

Syntax

(letrec* {bindings} {body})

{bindings} has the form:

(({variable1} {init1}) ...)

where each {init} is an expression, and {body} is a sequence of zero or more definitions followed by a sequence of one or more expressions. It is an error for a {variable} to appear more than once in the list of variables being bound.

Semantics: The {variable}’s are bound to fresh locations, each {variable} is assigned in left-to-right order to the result of evaluating the corresponding {init}, the {body} is evaluated in the resulting environment, and the values of the last expression in {body} are returned. Despite the left-to-right evaluation and assignment order, each binding of a {variable} has the entire letrec* expression as its region, making it possible to define mutually recursive procedures.

If it is not possible to evaluate each {init} without assigning or referring to the value of the corresponding {variable} or the {variable} of any of the bindings that follow it in {bindings}, it is an error. Another restriction is that it is an error to invoke the continuation of an {init} more than once.

(letrec* ((p
            (lambda (x)
              (+ 1 (q (- x 1)))))
          (q
            (lambda (y)
              (if (zero? y)
                  0
                  (+ 1 (p (- y 1))))))
          (x (p 5))
          (y x))
  y)
    => 5

list

(list obj ...)

Return a newly allocated list of its arguments.

list-copy

(list-copy lst)

Returns a newly allocated copy of the given obj if it is a list. Only the pairs themselves are copied; the cars of the result are the same (in the sense of eqv?) as the cars of list.

If obj is an improper list, so is the result, and the final cdrs are the same in the sense of eqv?. An obj which is not a list is returned unchanged.

It is an error if obj is a circular list.

(define a ’(1 8 2 8)) ; a may be immutable
(define b (list-copy a))
(set-car! b 3) ; b is mutable

b => (3 8 2 8)
a => (1 8 2 8)

list-ref

(list-ref lst k)

Returns the kth element of lst.

list-set!

(list-set! lst k obj)

Stores obj in element k of lst.

list-tail

(list-tail lst k)

Returns the sublist of lst obtained by omitting the first k elements.

list?

(list? o)

Returns #t if the given object is a list, and #f otherwise.

make-constructor

(make-constructor make name)

make-getter

(make-getter sym name idx)

make-list

(make-list k )

(make-list k fill)

Returns a newly allocated list of k elements. If a second argument is given, then each element is initialized to fill. Otherwise the initial contents of each element is unspecified.

make-parameter

(make-parameter init)

(make-parameter init converter)

Returns a newly allocated parameter object, which is a procedure that accepts zero arguments and returns the value associated with the parameter object.

make-setter

(make-setter sym name idx)

make-string

(make-string k)

(make-string k fill)

The make-string procedure returns a newly allocated string of length k. If fill char is given, then all the characters of the string are initialized to fill , otherwise the contents of the string are unspecified.

make-type-predicate

(make-type-predicate pred name)

map

(map proc list1 list2 ...)

The map procedure applies proc element-wise to the elements of the lists and returns a list of the results, in order.

If more than one list is given and not all lists have the same length, map terminates when the shortest list runs out. The lists can be circular, but it is an error if all of them are circular. It is an error for proc to mutate any of the lists. The dynamic order in which proc is applied to the elements of the lists is unspecified. If multiple returns occur from map, the values returned by earlier returns are not mutated.

(map cadr ’((a b) (d e) (g h)))
  => (b e h)

(map (lambda (n) (expt n n))
     ’(1 2 3 4 5))
  => (1 4 27 256 3125)

(map + ’(1 2 3) ’(4 5 6 7)) => (5 7 9)

max

(max x1 x2 ...)

max returns the largest of its arguments.

member

(member obj lst) 

(member obj lst compare)

Returns the first sublist of lst whose car is obj, where the sublists are the non-empty lists returned by (list-tail lst k) for k less than the length of lst.

If obj does not occur in list, then #f (not the empty list) is returned.

member uses compare to compare elements of the list, if given, and equal? otherwise.

memq

(memq obj lst)

The memq procedure is the same as member but uses eq? to compare obj with the elements of lst.

memv

(memv obj lst)

The memv procedure is the same as member but uses eqv? to compare obj with the elements of lst.

min

(min x1 x2 ...)

min returns the smallest of its arguments.

modulo

(modulo a b)

Return the integer remainder after dividing a by b.

negative?

(negative? n)

Returns #t if n is a negative number and #f otherwise. It is an error if n is not a number.

newline

(newline)

(newline port)

Write a newline to port, or the current output port if no argument is given.

not

(not x)

The not procedure returns #t if x is false, and returns #f otherwise.

numerator

(numerator n)

Return the numerator of n.

odd?

(odd? num)

Return #t if num is an odd number and #f otherwise.

open-input-bytevector

(open-input-bytevector bv)

Takes a bytevector and returns a binary input port that delivers bytes from the bytevector.

open-input-string

(open-input-string string)

Takes a string and returns a textual input port that delivers characters from the string.

open-output-bytevector

(open-output-bytevector open-output-string)

Returns a binary output port that will accumulate bytes for retrieval by get-output-bytevector.

open-output-string

(open-output-string)

Returns a textual output port that will accumulate characters for retrieval by get-output-string.

or

Syntax

(or {test1} ...)

Semantics: The {test} expressions are evaluated from left to right, and the value of the first expression that evaluates to a true value is returned. Any remaining expressions are not evaluated. If all expressions evaluate to #f or if there are no expressions, then #f is returned.

(or (= 2 2) (> 2 1)) => #t
(or (= 2 2) (< 2 1)) => #t
(or #f #f #f) => #f
(or (memq 'b '(a b c))
    (/ 3 0)) => (b c)

output-port-open?

(output-port-open? port)

Returns #t if port is an open output port, and #f otherwise.

output-port?

(output-port? obj)

Returns #t if obj is an output port, and #f otherwise.

parameterize

Syntax

(parameterize (({param1} {value1}) ...)

  {body})

positive?

(positive? n)

Returns #t if n is a positive number and #f otherwise.

quasiquote

Syntax

(quasiquote {qq template})

quotient

(quotient x y)

Return the quotient of dividing x by y.

raise

(raise obj)

Raises an exception by invoking the current exception handler on obj.

The handler is called with the same dynamic environment as that of the call to raise, except that the current exception handler is the one that was in place when the handler being called was installed. If the handler returns, a secondary exception is raised in the same dynamic environment as the handler.

raise-continuable

(raise-continuable obj)

Raises an exception by invoking the current exception handler on obj.

The handler is called with the same dynamic environment as the call to raise-continuable, except that: (1) the current exception handler is the one that was in place when the handler being called was installed, and (2) if the handler being called returns, then it will again become the current exception handler. If the handler returns, the values it returns become the values returned by the call to raise-continuable.

rational?

(rational? obj)

Returns #t if obj is a rational number and #f otherwise.

read-line

(read-line)

(read-line port)

Read a line of text from the current input port or port if specified.

read-string

(read-string k)

(read-string k port)

Read a string from the current input port or port if specified.

receive

Syntax

(receive {formals} {expression} {body})

record?

(record? obj)

Returns #t if obj is a record type and #f otherwise.

remainder

(remainder num1 num2)

Returns the remainder of dividing num1 by num2.

reverse

(reverse lst)

Returns a newly allocated list that is the reverse of lst.

round

(round z)

Returns the closest integer to z.

slot-set!

(slot-set! name obj idx val)

square

(square z)

Returns the square of z.

string

(string char ...)

Returns a string containing the given characters.

string->list

(string->list string)

(string->list string start)

(string->list string start end)

Returns a newly allocated list containing the characters of string.

string->utf8

(string->utf8 string)

(string->utf8 string start)

(string->utf8 string start end)

Returns a newly allocated bytevector containing the UTF-8 bytecodes of string.

string->vector

(string->vector string)

(string->vector string start)

(string->vector string start end)

Returns a newly allocated vector containing the contents of string.

string-copy

(string-copy string)

(string-copy string start)

(string-copy string end)

Returns a copy of string.

string-copy!

(string-copy! to at from)

(string-copy! to at from start)

(string-copy! to at from start end)

Copies the characters of string from between start and end to string to, starting at at.

(define a "12345")
(define b (string-copy "abcde"))
(string-copy! b 1 a 0 2)
b => "a12de"

string-fill!

(string-fill! str fill)

(string-fill! str fill start)

(string-fill! str fill start end)

The string-fill! procedure stores fill in the elements of str between start and end.

string-for-each

(string-for-each proc string1 string2 ...)

string-for-each is like for-each but the arguments consist of strings instead of lists.

string-map

(string-map proc string1 string2 ...)

string-maph is like map but the arguments consist of strings instead of lists.

string<=?

(string<=? str1 str2)

string<?

(string<? str1 str2)

string=?

(string=? str1 str2)

Returns #t if all of the given strings are equal and false otherwise.

string>=?

(string>=? str1 str2)

string>?

(string>? str1 str2)

symbol=?

(symbol=? symbol1 symbol2 symbol3 ...)

Returns #t if all of the arguments are the same symbol and #f otherwise.

syntax-error

Syntax

(syntax-error {message} {args} ...)

truncate

(truncate z)

truncate-quotient

(truncate-quotient quotient)

truncate-remainder

(truncate-remainder remainder)

truncate/

(truncate/ n m)

type-slot-offset

(type-slot-offset name sym)

unless

Syntax

(unless {test} {expression1} {expression2} ...)

Syntax: The {test} is an expression.

Semantics: The test is evaluated, and if it evaluates to #f, the expressions are evaluated in order. The result of the when expression is unspecified.

(unless (= 1 1.0)
  (display "1")
  (display "2")) => unspecified and prints nothing

utf8->string

(utf8->string bytevector)

(utf8->string bytevector start)

(utf8->string bytevector start end)

Convert bytecodes in the given bytevector to a string.

values

(values obj ...)

Return arguments received as multiple values.

vector

(vector obj ...)

vector returns a vector of its arguments.

vector->list

(vector->list vector)

(vector->list vector start)

(vector->list vector start end)

Return a newly-allocated list containing the contents of vector.

vector->string

(vector->string vector)

(vector->string vector start)

(vector->string vector start end)

Return a newly-allocated string containing the contents of vector.

vector-append

(vector-append vector ...)

Returns a newly allocated vector whose elements are the concatenation of the elements of the given vectors.

vector-copy

(vector-copy vector)

(vector-copy vector start)

(vector-copy vector start end)

Returns a newly allocated copy of the elements of the given vector between start and end. The elements of the new vector are the same (in the sense of eqv?) as the elements of the old.

vector-copy!

(vector-copy! to at from)

(vector-copy! to at from start)

(vector-copy! to at from start end)

Copies the elements of vector from between start and end to vector to, starting at at.

(define a (vector 1 2 3 4 5))
(define b (vector 10 20 30 40 50))
(vector-copy! b 1 a 0 2)
b => #(10 1 2 40 50)

vector-fill!

(vector-fill! vector fill)

(vector-fill! vector fill start)

(vector-fill! vector fill start end)

The vector-fill! procedure stores fill in the elements of vector between start and end.

vector-for-each

(vector-for-each proc vector1 vector2 ...)

vector-for-each is like for-each but the arguments consist of vectors instead of lists.

vector-map

(vector-map proc vector1 vector2 ...)

vector-map is like map but the arguments consist of vectors instead of lists.

when

Syntax

(when {test} {expression1} {expression2} ...)

Syntax: The {test} is an expression.

Semantics: The test is evaluated, and if it evaluates to a true value, the expressions are evaluated in order. The result of the when expression is unspecified.

(when (= 1 1.0)
  (display "1")
  (display "2")) => unspecified and prints 12

with-exception-handler

(with-exception-handler handler thunk)

The with-exception-handler procedure returns the results of invoking thunk. handler is installed as the current exception handler in the dynamic environment used for the invocation of thunk.

with-handler

Syntax

(with-handler handler expression1 expression2 ...)

with-handler provides a convenient exception handling syntax.

The expressions are executed in order and if no exceptions are raised the result of the last expression is returned. Otherwise if an exception is raised then handler is called and its results are returned.

write-char

(write-char char)

(write-char char port)

Write char to the current output port or port if specified.

write-string

(write-string string)

(write-string string port)

Write string to the current output port or port if specified.

zero?

(zero? n)

Returns #t if n is zero and #f otherwise.