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Re: Always-true predicate?
From: |
Andrea Corallo |
Subject: |
Re: Always-true predicate? |
Date: |
Wed, 17 Feb 2021 12:31:57 +0000 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
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
- Always-true predicate?, Lars Ingebrigtsen, 2021/02/17
- Re: Always-true predicate?,
Andrea Corallo <=
- Re: Always-true predicate?, Basil L. Contovounesios, 2021/02/17
- Re: Always-true predicate?, Pip Cet, 2021/02/17
- Re: Always-true predicate?, Lars Ingebrigtsen, 2021/02/17
- Re: Always-true predicate?, Pip Cet, 2021/02/17
- Re: Always-true predicate?, Lars Ingebrigtsen, 2021/02/17
- Re: Always-true predicate?, Teemu Likonen, 2021/02/17
- RE: [External] : Re: Always-true predicate?, Drew Adams, 2021/02/17