From Newsgroup: comp.lang.lisp

B. Pym wrote:

Kenny Tilton wrote:

KMP: The example you cite is quite simplistic.....snip...A
loop like this:

(loop for x from 0
for y in some-list
when (good-result? y)
collect (list x y))

is easy to write and maintain, and much easier to explain than the equivalent, but more Lispy:

(do ((x 0 (+ x 1))
(y-list some-list (cdr y-list))
(result '()))
((null y-list) ;; [fixed]
(nreverse result))
(let ((y (first y-list)))
(when (good-result? y)
(push (list x y) result))))

Ugh. Howse about:

(let ((goody-pos -1)
goodies)
(dolist (it some-list (nreverse goodies))
(incf goody-pos)
(when (good-result? it)
(push (list goody-pos it) goodies))))

perhaps i will be swayed someday by the charms of loop, but i gotta
tell you, i just don't get it. is loop for people who can't read lisp? can't be, lisp is easier to read than loop. stumped.

Gauche Scheme:

(use gauche.collection) ;; size-of

(filter-map
(lambda (x i)
(and (> (size-of x) 1) (list i x)))
'("a" "or" "I" "can" "o" "burn")
(liota))

===>
((1 "or") (3 "can") (5 "burn"))

(use srfi-42) ;; list-ec

(define some-list '((d) () (g) (o) () (w)))

(list-ec
(:list x (index i) some-list)
(if (pair? x))
(list i x))

===>
((0 (d)) (2 (g)) (3 (o)) (5 (w)))

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