Re: processing a sequence

joswig@....  wrote:

I am trying to process a sequence like:
>
(0 1 2 3 0 1 2 3 0 1 2 3)
>
and produce:
>
((0 1 2 3)(0 1 2 3)(0 1 2 3))
>
i.e. create sub-sequences beginning whenever the value decreases.
>

Gauche Scheme

(monotonic-slices '(0 1 2 3 0 1 2 3 0 1 2 3) + >)

  ===>
((0 1 2 3) (0 1 2 3) (0 1 2 3))


Given:

(define (each-mono-slice func LST :optional (KEY-FUNC values) (CMP equal?))
  (let ((RESULT '())  (TMP '())  (OLD-KEY 0)  (NEW-KEY 0))
    (dolist (X LST)
      (set! NEW-KEY (KEY-FUNC X))
      (cond ((null? TMP) (push! TMP X))
            ((CMP NEW-KEY OLD-KEY)
             (push! TMP X))
            (#t (func (reverse TMP)) (set! TMP (list X))))
      (set! OLD-KEY NEW-KEY))
    (unless (null? TMP) (func (reverse TMP)))
    (reverse RESULT)))

(define (monotonic-slices LST :optional (KEY-FUNC values) (CMP equal?))
  (let ((result '()))
    (each-mono-slice (lambda(xs) (push! result xs)) LST KEY-FUNC  CMP)
    (reverse result)))