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Function split list to lists of length n.

/ Published in: Scheme
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Function group-for which return list of list of length n.
(group-for '(1 2 3 4 5 6 7 8 9) 3)
=> ((1 2 3) (4 5 6) (7 8 9))

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  1. (define (skip list n)
  2.     (cond ((null? list) '())
  3.           ((<= n 0) list)
  4.           (else
  5.               (skip (cdr list) (- n 1)))))
  6.  
  7. (define (splice list n m)
  8.     (let loop ((stop (- m n)) (list (skip list n)))
  9.         (if (or (eq? stop 0) (null? list))
  10.             '()
  11.             (cons (car list) (loop (- stop 1) (cdr list))))))
  12.  
  13. (define (group-for list count)
  14.     (let ((step (/ (length list) count)))
  15.         (let loop ((i 0))
  16.             (if (eq? i count)
  17.                 '()
  18.                 (cons (splice list (* i count) (* (+ i 1) count)) 
  19.                       (loop (+ i 1)))))))

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