re-char char str ret)
  (let ((end (or (string-index str char)
		 (string-length str))))
    (ret (substring str 0 end)
	 (substring str end))))

(define (split-discarding-char char str ret)
  (let ((end (string-index str char)))
    (if (not end)
	(ret str "")
	(ret (substring str 0 end)
	     (substring str (1+ end))))))

(define (split-after-char-last char str ret)
  (let ((end (cond
	      ((string-rindex str char) => 1+)
	      (else 0))))
    (ret (substring str 0 end)
	 (substring str end))))

(define (split-before-char-last char str ret)
  (let ((end (or (string-rindex str char) 0)))
    (ret (substring str 0 end)
	 (substring str end))))

(define (split-discarding-char-last char str ret)
  (let ((end (string-rindex str char)))
    (if (not end)
	(ret str "")
	(ret (substring str 0 end)
	     (substring str (1+ end))))))

(define (split-before-predicate pred str ret)
  (let loop ((n 0))
    (cond
     ((= n (string-length str))		(ret str ""))
     ((not (pred (string-ref str n)))	(loop (1+ n)))
     (else				(ret (substring str 0 n)
					     (substring str n))))))
(define (split-after-predicate pred str ret)
  (let loop ((n 0))
    (cond
     ((= n (string-length str))		(ret str ""))
     ((not (pred (string-ref str n)))	(loop (1+ n)))
     (else				(ret (substring str 0 (1+ n))
					     (substring str (1+ n)))))))

(define (split-discarding-predicate pred str ret)
  (let loop ((n 0))
    (cond
     ((= n (string-length str))		(ret str ""))
     ((not (pred (string-ref str n)))	(loop (1+ n)))
     (else				(ret (substring str 0 n)
					     (substring str (1+ n)))))))

(define (separate-fields-discarding-char ch str ret)
  (let loop ((fields '())
	     (str str))
    (cond
     ((string-rindex str ch)
      => (lambda (w) (loop (cons (substring str (+ 1 w)) fields)
			   (substring str 0 w))))
     (else (apply ret str fields)))))

(define (separate-fields-after-char ch str ret)
  (reverse
   (let loop ((fields '())
             (str str))
     (cond
      ((string-index str ch)
       => (lambda (w) (loop (cons (substring str 0 (+ 1 w)) fields)
                           (substring str (+ 1 w)))))
      (else (apply ret str fields))))))

(define (separate-fields-before-char ch str ret)
  (let loop ((fields '())
	     (str str))
    (cond
     ((string-rindex str ch)
      => (lambda (w) (loop (cons (substring str w) fields)
			     (substring str 0 w))))
     (else (apply ret str fields)))))