Strips leading and trailing characters in the stripchars list off of a string and returns the stripped string.
The string to strip
A list of characters that should be stripped.
(define (strip str #!optional (stripchars '(#\space #\
#\U-0009)))
;; Strip leading and trailing characters off of a string
(let* ((startpos (let loop ((count 0))
(if (>= count (string-length str))
(string-length str)
(if (member (string-ref str count) stripchars)
(loop (+ count 1))
count))))
(tailstr (substring str startpos (string-length str)))
(endpos (let loop ((count (- (string-length tailstr) 1)))
(if (< count 1)
0
(if (member (string-ref tailstr count) stripchars)
(loop (- count 1))
count)))))
(if (or (< endpos 0)
(string=? tailstr ""))
""
(substring tailstr 0 (+ endpos 1)))))