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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp
Subject: Re: YANQ - When to map, when to iterate, when to recurse? And why CLOS?
Date: Mon, 19 Aug 2024 07:20:00 -0000 (UTC)
Organization: A noiseless patient Spider
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Wade Humeniuk wrote:

> John Connors wrote: 
> 
> > Yet Another Noob Question. 
> 
> > What are the characteristics of each implementation? 
> 
> > How can I tell which I should be writing in what context... 
> 
> > (defun find-indicies (lst tst) 
> >   (let ((li 0)) 
> >     (labels ((qpred (a) 
> >                (incf li) 
> >                (if (funcall tst a) 
> >                    (1- li) 
> >                    nil))) 
> >       (remove nil (mapcar #'qpred lst))))) 
> 
> > (defun find-indices (lst tst) 
> >   (loop 
> >    for el in lst 
> >    counting t into index 
> >    if (funcall tst el) 
> >    collect index)) 
> 
> You are allergic to loop 
> 
> (defun find-indices (list test) 
>    (loop for element in list 
>          for index from 1 
>          when (funcall test element) collect index))

newLISP

(define (find-indices lst test)
  (index test lst))

(find-indices '(200 209 250 257 260 263) odd?)
  ===>
(1 3 5)