Re: 21.1 incorrect Regular expression parsing

[Stefan Monnier]

>>> (string-match "[0-9]++" "12")
> | Where have you seen it documented as "not valid" ?
> I'm not sure I understand your question. If you mean that we need a
> section from POSIX documentation before, I'm afraid I cannot provide
> one. I guess the official chapter may label the behavior "undefined."

What I meant was "what makes you think it is not valid?".
I indeed don't think POSIX defines them as not-valid but since Emacs
regexps do not implement POSIX, it's not necessarily relevant (although
I did try to make the regexp engine a bit more POSIX compliant).

> I understand this to be a regular expressing bug and It would be good
> if Emacs signalled error.
> For reference - I checked XEmacs 21.4.3 and it signals error.

But Emacs-20.7 doesn't.  For compatibility reasons, I'd only consider
changing the behavior if there's a compelling reason to do so,
and I fail to see any.


        Stefan