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Construction of Strings

procedure: make-string k [char]

Returns a newly allocated string of length k. If you specify char, all elements of the string are initialized to char, otherwise the contents of the string are unspecified. Char must satisfy the predicate char-ascii?.

(make-string 10 #\x)              =>  "xxxxxxxxxx"

procedure+: string char ...

Returns a newly allocated string consisting of the specified characters. The arguments must all satisfy char-ascii?.

(string #\a)                                =>  "a"
(string #\a #\b #\c)                        =>  "abc"
(string #\a #\space #\b #\space #\c)        =>  "a b c"
(string)                                    =>  ""

For compatibility with old code, char->string is a synonym for this procedure.

procedure: list->string char-list

Char-list must be a list of ASCII characters. list->string returns a newly allocated string formed from the elements of char-list. This is equivalent to (apply string char-list). The inverse of this operation is string->list.

(list->string '(#\a #\b))               =>  "ab"
(string->list "Hello")                  =>  (#\H #\e #\l #\l #\o)

procedure: string-copy string

Returns a newly allocated copy of string.

Note regarding variable-length strings: the maximum length of the result depends only on the length of string, not its maximum length. If you wish to copy a string and preserve its maximum length, do the following:

(define (string-copy-preserving-max-length string)
  (let ((length))
    (dynamic-wind 
     (lambda ()
       (set! length (string-length string))
       (set-string-length! string (string-maximum-length string)))
     (lambda ()
       (string-copy string))
     (lambda ()
       (set-string-length! string length)))))

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