From: Adam Porter <adam@alphapapa.net>
To: emacs-devel@gnu.org
Subject: Re: Make regexp handling more regular
Date: Wed, 02 Dec 2020 22:16:45 -0600 [thread overview]
Message-ID: <87y2ifsevm.fsf@alphapapa.net> (raw)
In-Reply-To: 87lfeg60iy.fsf@gnus.org
Lars Ingebrigtsen <larsi@gnus.org> writes:
> I constant source of confusion and subtle bugs is the way Emacs does
> regexp match handling: The way `string-match' (and the rest) sets a
> global state, and you sort of have to catch them "early" is often a
> challenge for new users.
>
> Experienced Emacs Lisp programmers know to be safe and will say:
>
> (when (string-match "[a-z]" string)
> (let ((match (match-string 0 string)))
> (foo)
> (bar match)))
>
> while people new to Emacs Lisp will expect this to work:
>
> (when (string-match "[a-z]" string)
> (foo)
> (bar (match-string - string)))
>
> And sometimes it does, and sometimes it doesn't, depending on whether
> `foo' also messes with the match data.
>
> So my idle shower thought for the day is: Is there any reasonable path
> forward that the Emacs Lisp language could take here?
It's funny that you should post this today, Lars, because I just
encountered this very problem while using code from your format-spec
function in combination with code from your shr-insert-document function
(the latter of which changed the match data, making the former fail
inexplicably...until I figured it out). Not that I'm blaming you, of
course--it's me who's using your code in unintended ways. :)
Anyway, I'd be very happy if Emacs had "safer" matching functions like
this. And I like the idea of prefixing them with "rx-", as was
suggested.
Thanks for your work on Emacs!
prev parent reply other threads:[~2020-12-03 4:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 9:05 Make regexp handling more regular Lars Ingebrigtsen
2020-12-02 10:44 ` Lars Ingebrigtsen
2020-12-02 11:12 ` Stefan Kangas
2020-12-02 11:21 ` Philipp Stephani
2020-12-03 8:31 ` Lars Ingebrigtsen
2020-12-02 17:17 ` Stefan Monnier
2020-12-02 17:45 ` Yuan Fu
2020-12-02 19:24 ` Stefan Monnier
2020-12-03 8:40 ` Lars Ingebrigtsen
2020-12-03 8:38 ` Lars Ingebrigtsen
2020-12-03 15:10 ` Stefan Monnier
2020-12-03 16:58 ` Lars Ingebrigtsen
2020-12-03 17:40 ` Stefan Monnier
2020-12-02 21:19 ` Juri Linkov
2020-12-03 8:41 ` Lars Ingebrigtsen
2020-12-03 15:00 ` Stefan Monnier
2020-12-03 21:02 ` Juri Linkov
2020-12-03 22:20 ` Vasilij Schneidermann
2020-12-02 21:28 ` Daniel Martín
2020-12-03 4:16 ` Adam Porter [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87y2ifsevm.fsf@alphapapa.net \
--to=adam@alphapapa.net \
--cc=emacs-devel@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.