;;seperate a long line into pieces, each fitting into a smaller line.
(define (seperate-line line width)
  (let loop ((new '())
	     (old line))
    (if (> width (string-length old))
	(if (= 0 (string-length old))
	    (if (equal? new '())
		'("")
		new)
	    (append (list old) new))
	(let ((next-line (substring old 0 width))
	      (rest-old (substring old width (string-length old))))
	  (loop (cons next-line new) rest-old)))))

;;the result is the "answer" of scsh
(define (layout-result-standard result-str width)
  (reverse (seperate-line result-str width)))

;useful helpers
;;; EK: useful for what=
(define (get-marked-positions-1 all-items marked-items)
  (let loop ((count 0)
	     (result '()))
    (if (>= count (length all-items))
	result
	(let ((act-item (list-ref all-items count)))
	  (if (member act-item marked-items)
	      (loop (+ count 1)
		    (append result (list (+ count 1))))
	      (loop (+ count 1) result))))))

(define (get-marked-positions-2 all-items marked-items)
  (let loop ((count 0)
	     (result '()))
    (if (>= count (length all-items))
	result
	(let ((act-item (list-ref all-items count)))
	  (if (member act-item marked-items)
	      (loop (+ count 1)
		    (append result (list (+ count 2))))
	      (loop (+ count 1) result))))))

(define (get-marked-positions-3 all-items marked-items)
  (let loop ((count 0)
	     (result '()))
    (if (>= count (length all-items))
	result
	(let ((act-item (list-ref all-items count)))
	  (if (member act-item marked-items)
	      (loop (+ count 1)
		    (append result (list (+ count 3))))
	      (loop (+ count 1) result))))))

;;expression as string
(define (exp->string exp)
  (let ((exp-port (open-output-string)))
    (write exp exp-port)
    (get-output-string exp-port)))

(define (sublist l pos k)
  (let ((tmp (list-tail l pos)))
    (reverse (list-tail (reverse tmp) 
			(- (length tmp) k)))))