(define (range lo hi)
(if (>= hi lo)
(build-list (+ (- hi lo) 1) (lambda (i) (+ lo i)))
(build-list (+ (- lo hi) 1) (lambda (i) (- lo i)))))
(define (sort2 l) (sort l (lambda (i j) (< (second i) (second j)))))
-- Matthias
On Apr 1, 2009, at 10:39 PM, David Vanderson wrote:
Matthias Felleisen wrote:
(define (fence s n)
(define is (shared ((x (append (range 1 n) (range (- n 1) 2)
x))) x))
(define wv (for/list ((c s)) (begin0 (list c (car is)) (set! is
(cdr is)))))
(map first (sort2 wv)))
I very much enjoyed trying my hand at this problem and then
figuring out how this function works. But I couldn't find "range"
or "sort2" in the PLT docs. Are those functions that seasoned
schemers are assumed to know about and have on hand?
Thanks,
Dave
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