On Fri, Jan 12, 2024 at 3:05 AM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> I don't think there's a clear enough need for it right now in Emacs core
> to motivate its integration in Emacs proper. Also, because several
> people have expressed an opinion that leans towards recommending that
> Emacs's own code should probably better avoid using this functionality.
Those people are trying to come up with alternative pattern-matching
libraries which we start to see are not simpler or as powerful
as pcase.
But sure, other pattern-matching libraries exist out there. See
CL's optima/trivia [1/2] for some very good ones. Emacs just happens
to have pcase readily available.
> I'd be quite happy to include such a think in GNU ELPA, OTOH.
Could be, but why really? Why are CL things which rest on such
high-quality well-known designs, older than many things Emacs,
relegated to a place where they're less discoverable?
Here, I think at least the new fresh implementation of
lambda-list parsing (which is the meat-and-bones of this patch)
is worth taking a look at.
It's the function 'cl--pcase-cl-lambda-var-groups'.
I would definitely consider grooming this function, renaming
it, and keeping it in core, exposing to general Elisp usage
in cl-macs.el (or cl-lambdalist.el, cl-ll.el), even if a new
pcase pattern that uses it goes to ELPA (but why, really?)
That util could help us write other lambda-list destructuring
alternatives that understand &optional, &rest. Because with or
without it, we already use a lot of the &optional, &rest explicitly
in Emacs. And we also use &key and &allow-other-keys in many other
places, though sometimes in ad-hoc lets-not-call-this-bull-by-its-name
fashion.
IOW there is no general purpose-util like Alexandria's
'parse-ordinary-lambda-list', and this could be it. It could
not only be used to simplify and add coherence to many of these
existing compile-time structures, for example helping simplify
things and address FIXMEs in cl-lib.el.
João
[1] https://github.com/m2ym/optima
[2] https://github.com/guicho271828/trivia