string-splitter.scm

;; split a string with a token-list
;; eg.
;; (string-split "dccdd53cccdd" '(#\c #\d))-> ("d" "c" "c" "d" "d" "53" "c" "c" "c" "d" "d" "")
;; (string-split "demo, char., detecting " '(#\c #\d)) -> ("d" "emo, " "c" "har., " "d" "ete" "c" "ting ")
(define (string-split string token-list)
  (define temp-string "")
  (string-split-iter token-list string temp-string '()))
  
  (define (string-split-iter token-list rest-string temp-string result-list)
    (define rest-str-len (string-length rest-string))
    (define 1st-char (if (>  (string-length rest-string) 0) (string-ref rest-string 0) ""))
    (cond ((eq? rest-str-len 0)
         (append result-list (list temp-string)))
      ((memq 1st-char token-list)
       (string-split-iter
        token-list
         (substring rest-string 1 rest-str-len)
        ""
        (if (eq? (string-length temp-string) 0) (append result-list (list (string 1st-char)))
           (append result-list (list temp-string (string 1st-char))
           ))))
      (else 
           (string-split-iter
            token-list
            (substring rest-string 1 rest-str-len)
            (string-append temp-string (string 1st-char))
            result-list)
           )
))