bug#26338: 26.0.50; Collect all matches for REGEXP in current buffer

[Drew Adams <drew.adams@oracle.com>]

> Regarding Drew's concerns about extending cl-loop with more non-Common
> Lisp things, I just don't see that as a problem.

It depends on what one considers "a problem".  I think it
is a problem for `cl-', which was intended for Common Lisp
emulation, to become a dumping ground for anyone's idea of
a cool thing to add to Emacs.  That's not what it's for.

We've already had a couple of things unrelated to CL that
were misguidedly added to `cl-'.  We should not continue
that practice (and we really should remove those from the
`cl-' namespace).

There is nothing preventing Emacs from adding any constructs
it wants.  There just is no reason why the `cl-' namespace
(and the `cl*.el' files) should be polluted with stuff that
is not Common Lisp emulation.

A user of `cl-loop' should be able to expect Common Lisp
`loop', or as close to it as we can get.

> I suppose it would be nice to have a more easily extensible
> looping macro, like iterate [1].  That would be quite a bit
> of work though.

As for `iterate': If this is what you mean:
https://common-lisp.net/project/iterate/

then I'm all in favor of it.  I much prefer it to `loop'.
But I don't see anyone stepping forward to add it to Emacs.

Even then, I would probably prefer that we add it to the
`cl-' namespace and stay as close as possible to emulating
the Common Lisp `iterate' (no, it is not part of the CL
language, but yes, it is something developed for/with CL).

There are lots of users of CL, and lots of CL code.  Both
should find a simple, straightforward path to Emacs.  We
should minimize any differences between Emacs emulations
and the things being emulated.

But again, nothing prevents Emacs adding a different
construct that does exactly what you want, with all the
bells and whistles you think are improvements over `loop'
or `iterate' or whatever.

That should not be in the `cl-' namespace, and we should
not confuse users by passing it off as (even a partial)
emulation of a Common Lisp construct.  That's all.

Just one opinion.