Re: [PATCH] add compiled regexp primitive lisp object

["Björn Bidar" <bjorn.bidar@thaodan.de>]

Ihor Radchenko <yantar92@posteo.net> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> 2. They could maybe even be constructed from Elisp, opening
>>>    opportunities for custom regexp compilers that can be tailored to
>>>    specific application needs rather than having to stick to hard-coded
>>>    generic tradeoffs Emacs has to do without knowing the purpose of a
>>>    regexp.
>>
>> How will this help making matching faster, and why does this have to
>> be via compiled regexp objects?
>
> My motivation is
> https://burntsushi.net/regex-internals/#literal-extraction that explains
> how regexp compilation depends on certain heuristics.
>
> For example, when searching for "\\(foo\\|bar\\)[a-z]+", heuristics
> invoking simple string literal search for "foo" and "bar" first before
> using heavy regexp automata is justified. Not so much when the prefix is
> simply " " that usually occurs very frequently in text.

I want to highlight that is example would already cover many of the
operations which modes do for example for fontification or
text-extraction.