From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Robert Pluim Newsgroups: gmane.emacs.bugs Subject: bug#58278: Add new function seq-keep Date: Tue, 04 Oct 2022 12:05:51 +0200 Message-ID: <87lepvaoow.fsf@gmail.com> References: <87y1twtx22.fsf@bernoul.li> <87pmf84ggg.fsf@gnus.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="8290"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 58278@debbugs.gnu.org, Jonas Bernoulli To: Lars Ingebrigtsen Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Tue Oct 04 12:07:12 2022 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1ofepT-0001wY-Tw for geb-bug-gnu-emacs@m.gmane-mx.org; Tue, 04 Oct 2022 12:07:11 +0200 Original-Received: from localhost ([::1]:43690 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ofepS-0005gb-MN for geb-bug-gnu-emacs@m.gmane-mx.org; 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Tue, 04 Oct 2022 03:05:52 -0700 (PDT) In-Reply-To: <87pmf84ggg.fsf@gnus.org> (Lars Ingebrigtsen's message of "Tue, 04 Oct 2022 01:47:59 +0200") X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:244380 Archived-At: >>>>> On Tue, 04 Oct 2022 01:47:59 +0200, Lars Ingebrigtsen said: Lars> Jonas Bernoulli writes: >> Unfortunately I cannot find a replacement for `-keep', which I have been >> using a lot. I propose that we add something like: >> >> (cl-defgeneric seq-keep (pred sequence) >> "Return a list of all non-nil results of (PRED element) for elements in SEQUENCE." >> (delq nil (seq-map (lambda (elt) (funcall pred elt)) >> sequence))) Lars> Hm... well, here PRED isn't a predicate, really, but a transforming Lars> function? But you wish to filter out the nil results of that Lars> transforming function. Lars> That sounds useful -- there's more than a 100 matches for "delq Lars> nil.*map" in-tree only -- but it's slightly confusing that the function Lars> isn't altogether a predicate, but only kinda. Would a function Lars> signature like Lars> (cl-defgeneric seq-keep (function sequence &optional pred) Lars> ...) Lars> make more sense for this combination of map/filter? (The default Lars> predicate would, of course, be "not null".) How is this different from 'cl-mapcan'? (apart from the syntactic sugar) Robert --