Remove whitespace from string

Problem

Remove extraneous whitespace (i.e. space, tab, newline) characters from a string.

Solution

Using SRFI 13

These can remove arbitrary characters, but the default is to remove whitespace:

• (string-trim s)
• (string-trim-right s)
• (string-trim-both s)

Using regular expressions

(define string-trim-both
  (let ((r (regexp "^[ \t\r]*(.*?)[ \t\r]*$")))
    (lambda (s)
      (cadr (regexp-match r s)))))

The regular expression picks out the middle of the string. It is compiled only once, namely when string-trim-both is defined.

The regexp and regexp-match procedures are from Racket. Equivalent procedures exist for some other implementations, and in SRFI 115.

Credit: Jens Axel Søgaard

Usage

(string-trim-both " foo ")
;; ==> "foo"

(string-trim-both " foo bar ")
;; ==> "foo bar"

(string-trim-both " foo bar")
;; ==> "foo bar"

(string-trim-both "foo bar")
;; ==> "foo bar"

(string-trim-both "")
;; ==> ""

(string-trim-both "   ")
;; ==> ""

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