Re: A faster derived-mode-p

[Óscar Fuentes]

"Basil L. Contovounesios" <contovob@tcd.ie> writes:

> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> On 14.02.2021 22:22, Lars Ingebrigtsen wrote:
>>> There are only 11K commands in the Emacs tree, so I don't know whether
>>> the current default completion predicate is going to turn out to be
>>> problematically slow or not.
>>
>> I just evaluated
>>
>>   (length (cl-delete-if-not #'commandp obarray))
>>
>> in a running Emacs session with a bunch of third-party packages installed and
>> loaded, and that still evaluated only to 1083.
>
> That's not counting the obarray's buckets.  I get ~6x as many results in
> my session with (length (all-completions "" obarray #'commandp)).

~10000 here.

Can't we memoize derived-mode-p ? It doesn't look like something that
could take a lot of space.