Re: Lookarounds and recursion in Emacs regexes

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 04 Feb 2023 17:28:11 -0500
> From:  Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>
> 
> There's a common confusion that ELisp is some kind of extension language
> for Emacs.  That's not quite true.  ELisp is an *implementation*
> language of Emacs (along with C for the other half).

That depends on what one considers as "Emacs" and what as
"extensions".

And besides, given that Emacs extends itself, what exactly are the
significant and fundamental differences between "extension language"
and "implementation language"?


> It doesn't prevent adding other extension languages, nor even does it
> necessarily prevent changing the implementation language to another one
> in theory.

Indeed, but replacing ELisp would probably need to rewrite a lot of
internals currently implemented in C, since most, if not all, of them
are currently very tightly coupled with Lisp and assume the existence
and design/implementation of various aspects of the Lisp machine.