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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: getting list of keys
Date: Fri, 30 Aug 2024 22:27:57 -0000 (UTC)
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> > an `update' function for the mp3 database.
> > I need a function for doing something like this with a list:
> >
> > * (xxxx (list :artist "something" :song "sss"))
> > => (:artist :song)
> >
> > Thanks in advance, and sorry for my bad english.
> > --
> > Pablo.
> 
> CL-USER> (loop :for (x y) :on (list :artist "something" :song "sss") :by #'cddr
>             :collect x)
> (:ARTIST :SONG)

Gauche Scheme and Racket using unfold from SRFI-1.

(use srfi-1)  ;; unfold for Gauche
  or
(require srfi/1)  ;; unfold for Racket

(unfold null? car cddr '(:artist "something" :song "sss"))
  ===>
(:artist :song)