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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp
Subject: Re: MAP (and variants) vs LOOP - Popular opinion observation?
Date: Wed, 18 Jun 2025 20:50:07 -0000 (UTC)
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Nathan Baum wrote:

> Then suppose you later need the loop/map to collect some of the values
> under certain conditions. You might have
> 
>    (loop for x in (get-list)
>          for i from 0
>          do (format t "~A - ~A~%" i x)
>          if (test x)
>          collect (foo x))

Gauche Scheme

(filter-map
  (lambda (x i)
    (print i " - " x)
    (and (odd? x) (square x)))
  '(0 2 3 5 6 9)
  (liota))

  ===>
0 - 0
1 - 2
2 - 3
3 - 5
4 - 6
5 - 9
(9 25 81)