[Jscheme-user] Re: easy way to break list up?

[Ken A. <kan...@bb...>]

Yes,
In elf/sort.scm there is (by n xs):

(define (by n xs)
  (define (by0 i xs items so-far)
    (if (= i 0) (by0 n xs '() (cons (reverse items) so-far))
        (if (null? xs) (finish items so-far)
            (by0 (- i 1) (cdr xs) (cons (car xs) items) so-far))))
  (define (finish items so-far)
    (reverse
     (if (null? items) so-far
         (cons (reverse items) so-far))))
  (assert (> n 0))
  (by0 n xs '() '()))

I think i got this idea from Peter Norvig:
Put parens around your data any way it comes and use (by) and (map) to
organize it into the way you want it.

k

At 05:36 PM 11/7/2002, Renu Kurien Bostwick wrote:

>Ken - 
>
>Do you know of an easy way (jscheme function perhaps) that'll break up
>a list into sublists that are max of n long?
>
>'(a b c d e f g h i j) with n=3 would become
>
>'((a b c) (d e f) (g h i) (j)) 
>
>or 
>
>'((a) (b c d) (e f g) (h i j))
>
>The ordering isn't important to me.  I've been writing my own function
>to do the split but it involves converting to vectors and back to
>lists.  Is there a more elegant solution?
>
>Thanks,
>Renu
>
>-- 
>-----------------------
>Renu Kurien Bostwick
>re...@bb...
>(617) 873-4543
>-----------------------