Subject: bug#58727: 29.0.50; rx doc: Semantics of RX...

From: Michael Heerdegen <[email-masked]>
Date: Mon, 24 Oct 2022 04:34:09 +0200

Mattias Engdegård <[email-masked]> writes:

> > The resulting regexps are concatenating like with an implicit `seq'.
> > This is not trivial, though: in stringish regexps the repetition
> > operators are only unary, and different interpretations would make sense
> > for `rx' (implicit `seq', implicit `or').
>
> The rule is implicit concatenation unless specified otherwise; maybe
> we could say that in the leading paragraph. (`or` is the only place
> where concatenation isn't done.)

Yes, that would be good.

> > Oh, and maybe let's also make more clear that `rx' always cares
> > about implicit grouping when necessary.
>
> No, there is no such thing in rx.

I think you misunderstood what I meant, I meant the implicit shy
grouping added in the return value, as in

  (rx (or "ab" "cd")) ==> "\\(?:ab\\|cd\\)"
                           ^^^^^       ^^^
> The manual provides corresponding string-notation constructs for
> orientation only.  This is important -- rx forms are defined by their
> semantics, not by what strings they translate to.

Is this trivial however?  Is it clear that, even for people that see rx
more as a translator to stringish regexps, `rx' is that smart?

A sentence like "rx forms are defined by their semantics" would help to
make that clear I think.
Dunno, I'm just guessing that here is a potential for misunderstanding.

Telling about the implicit concatenation of RX... is the more important
point for me.

Thanks so far,

Michael.