From: Andrea Corallo via "Emacs development discussions." <emacs-devel@gnu.org>
To: Lars Ingebrigtsen <larsi@gnus.org>
Cc: emacs-devel@gnu.org
Subject: Re: Always-true predicate?
Date: Wed, 17 Feb 2021 12:31:57 +0000 [thread overview]
Message-ID: <xjfo8giri2q.fsf@sdf.org> (raw)
In-Reply-To: <875z2qoqc6.fsf@gnus.org> (Lars Ingebrigtsen's message of "Wed, 17 Feb 2021 13:01:45 +0100")
Lars Ingebrigtsen <larsi@gnus.org> writes:
> Currently, Emacs has:
>
> ----
> Sometimes, when you call a functional, it is useful to supply a no-op
> function as the argument. Here are two different kinds of no-op
> function:
>
> -- Function: identity argument
> This function returns ARGUMENT and has no side effects.
>
> -- Function: ignore &rest arguments
> This function ignores any ARGUMENTS and returns ‘nil’.
> ----
>
> `identity' is kinda-sorta used as the opposite of `ignore' many places
> where you're feeding predicates to functions, but takes only one
> parameter and, of course, returns nil if you give it nil.
>
> Would it make sense to add a function that's exactly the opposite of
> `ignore' (for symmetry and convenience)? If so, what would it be
> called?
>
> I've googled to see what other languages do. Rust and NPM has "always",
> and many more Java-inspired frameworks have "truePredicate", but this
> isn't trivial to google for...
Maybe something like CONSTANTLY would be more generic?
<http://www.lispworks.com/documentation/HyperSpec/Body/f_cons_1.htm>
Andrea
next prev parent reply other threads:[~2021-02-17 12:31 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 12:01 Always-true predicate? Lars Ingebrigtsen
2021-02-17 12:31 ` Andrea Corallo via Emacs development discussions. [this message]
2021-02-17 12:40 ` Lars Ingebrigtsen
2021-02-17 16:59 ` Barry Fishman
2021-02-19 15:24 ` Stefan Kangas
2021-02-17 13:16 ` Basil L. Contovounesios
2021-02-17 18:56 ` Pip Cet
2021-02-17 19:19 ` Lars Ingebrigtsen
2021-02-17 19:31 ` Pip Cet
2021-02-17 19:37 ` Lars Ingebrigtsen
2021-02-17 20:18 ` Teemu Likonen
2021-02-17 22:25 ` [External] : " Drew Adams
2021-02-17 23:04 ` Basil L. Contovounesios
2021-02-17 23:13 ` Drew Adams
2021-02-17 23:01 ` Stefan Monnier
2021-02-19 11:27 ` Pip Cet
2021-02-19 15:07 ` Stefan Monnier
2021-02-19 19:04 ` Pip Cet
2021-02-19 20:11 ` Stefan Monnier
2021-02-20 9:40 ` Pip Cet
2021-02-20 13:58 ` Stefan Monnier
2021-02-19 5:39 ` Richard Stallman
2021-02-19 8:52 ` Robert Pluim
2021-02-19 9:10 ` Eli Zaretskii
2021-02-19 12:12 ` Eli Zaretskii
2021-02-19 12:52 ` Stefan Kangas
2021-02-19 13:00 ` Lars Ingebrigtsen
2021-02-19 13:34 ` Eli Zaretskii
2021-02-19 13:40 ` Lars Ingebrigtsen
2021-02-19 13:53 ` Eli Zaretskii
2021-02-19 14:05 ` Lars Ingebrigtsen
2021-02-19 18:04 ` [External] : " Drew Adams
2021-02-19 14:42 ` Stefan Monnier
2021-02-20 12:47 ` Lars Ingebrigtsen
2021-02-20 12:49 ` Lars Ingebrigtsen
2021-02-20 14:03 ` Stefan Monnier
2021-02-20 14:20 ` Lars Ingebrigtsen
2021-02-20 14:55 ` Stefan Monnier
2021-02-20 15:05 ` Lars Ingebrigtsen
2021-02-20 15:21 ` Stefan Monnier
2021-02-21 12:50 ` Robert Pluim
2021-02-21 13:04 ` Lars Ingebrigtsen
2021-02-19 15:09 ` Stefan Kangas
2021-02-19 15:22 ` Eli Zaretskii
2021-02-19 18:17 ` [External] : " Drew Adams
2021-02-19 18:41 ` Eli Zaretskii
2021-02-22 5:02 ` chad
2021-02-22 15:20 ` Eli Zaretskii
2021-02-22 23:07 ` chad
2021-02-21 6:12 ` Richard Stallman
2021-02-21 15:12 ` Eli Zaretskii
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