bug#72754: 31.0.50; Add a pcase-pattern-let?

bug#72754: 31.0.50; Add a pcase-pattern-let?

[Michael Heerdegen via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hello,

wouldn't it be a significant improvement and maybe a low hanging fruit
to add a macro allowing to add local pattern definitions?  I.e., like
`macrolet' by for pcase patterns?

It could help to make larger patterns better readable, by factoring out
long or repeatedly appearing patterns and giving them meaningful names.
Without cluttering the global namespace.

Maybe an implementation could be similar and as simple as that of
`rx-let'?


TIA,

Michael.

bug#72754: 31.0.50; Add a pcase-pattern-let?

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> wouldn't it be a significant improvement and maybe a low hanging fruit
> to add a macro allowing to add local pattern definitions?  I.e., like
> `macrolet' by for pcase patterns?

I don't know how important/useful it would be, but yes it would make
a lot of sense.  As a matter of fact, it's a general pattern which
recurs in all the packages which provide an extensible domain specific
language (peg.el, pcase.el, bindat.el, rx.el, gv.el, ...) and I'd like
to find a general solution.

It can also make sense to allow defining a set of extensions at one
place, and then make them available locally.


        Stefan

bug#72754: 31.0.50; Add a pcase-pattern-let?

[Michael Heerdegen via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> > wouldn't it be a significant improvement and maybe a low hanging fruit
> > to add a macro allowing to add local pattern definitions?  I.e., like
> > `macrolet' by for pcase patterns?
>
> I don't know how important/useful it would be, but yes it would make
> a lot of sense.  As a matter of fact, it's a general pattern which
> recurs in all the packages which provide an extensible domain specific
> language (peg.el, pcase.el, bindat.el, rx.el, gv.el, ...) and I'd like
> to find a general solution.

Makes sense, we could then also implement the dynamical docstring
generation for all of these in a general way.  As whole it's a bigger
project, though.

> It can also make sense to allow defining a set of extensions at one
> place, and then make them available locally.

Absolutely.

If you want to give it a try, I'm here...


Michael.