Re: rx and rx-to-string handle (regexp VAR) differently

["Kévin Le Gouguec" <kevin.legouguec@gmail.com>]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Platon Pronko <platon7pronko@gmail.com> writes:
>
>> rx-to-string docs explicitly say: "The arguments to ‘literal’ and
>> ‘regexp’ forms inside FORM must be constant strings."
>
> Is this a correct way to get what Kévin wants?
>
> #+begin_src emacs-lisp
>   (setq foo-regexp "fo+")
>   (rx-define foo (eval `(regexp ,foo-regexp)))
> #+end_src

Ah, nice catch!  I had started messing around with rx's 'eval', but
figured I should sort out my understanding of 'regexp' before throwing
more indirection at the problem.  It does seem like it fits my original
use-case better:

  (eval-and-compile
    (put 'foo 'rx-definition
         '((eval
            `(regexp ,foo-regexp))))
    'foo)

AFAICT (from that expansion and some cursory testing) that does allow
for (rx-to-string '(seq foo)) to change whenever foo-regexp changes.

> This also works in both cases:
>
> #+begin_src emacs-lisp
>   (setq foo-regexp '(regexp "fo+"))
>   (rx-define foo (eval foo-regexp))
> #+end_src

Noted.  Thanks a bunch for these hints!