bug#66554: [PATCH] Add the public API of Compat to the core

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Thu, 18 Jan 2024 12:33:31 -0800
> Cc: mail@daniel-mendler.de, 66554@debbugs.gnu.org, monnier@iro.umontreal.ca
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> +** New package Compat
> >> +The Compat package on GNU ELPA provides forwards-compatibility
> >> +support, so that packages that still provide support for older
> >
> > I think this is known as "backward compatibility".
> 
> AFAIU, backwards-compatibility is about making code written for Emacs 28
> work without changes on Emacs 29 (N -> N+1).
> 
> But forwards-compatibility is about making code written for Emacs 29
> work without changes on Emacs 28 (N -> N-1).
> 
> Compat is doing the latter.

AFAIU, Compat allows Lisp programs written for newer Emacs version to
work with older Emacs versions.  This makes those Lisp programs
compatible with old versions of Emacs, and in my book this is
backwards-compatibility.  But if I'm the only one who thinks that, so
be it.