Re: Always-true predicate?

[Barry Fishman]

On 2021-02-17 13:40:14 +01, Lars Ingebrigtsen wrote:
> Andrea Corallo <akrl@sdf.org> writes:
>
>> Maybe something like CONSTANTLY would be more generic?
>> <http://www.lispworks.com/documentation/HyperSpec/Body/f_cons_1.htm>

> I'm not sure that's a net win.  The use case here is, for instance
>
> (defalias 'mouse-sel--ignore #'ignore)
> (defvar after-focus-change-function #'ignore
>
> etc, which is fast and easy to read.  If you're doing a predicate, you
> now have to say
>
> (setq some-predicate #'ignore)
>
> but
>
> (setq some-predicate (lambda (&rest _) t))
>
> or
>
> (setq some-predicate (constantly t))
>
> which seems unsymmetric.

Something symmetric would be:

(setq some-predicate (constantly nil))

Ignore seems more about its lack of effects rather than its return value.

--
Barry Fishman