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Re: using non-Emacs regexp syntax

From: Jari Aalto
Subject: Re: using non-Emacs regexp syntax
Date: 29 Nov 2006 22:53:22 +0200
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4

Paul Pogonyshev <address@hidden> writes:

> David Kastrup wrote:
> > "Drew Adams" <address@hidden> writes:
> > 
> > >>     Is there a function to convert non-Emacs regexps (e.g. "ab(c+|d)" to
> > >>     Emacs regexps (example to "ab\(c+\|d\)")?
> > >>
> > >> The first form appears to be an "extended regexp" or egrep-style regexp.
> > >> The second appears to be a "basic regexp" or grep-style regexp.
> > >>
> > >> This conversion feature in Lisp would be useful to add after the release.
> > >
> > > Very glad to hear that.
> > >
> > > I'm hoping there will also be support for toggling the newline sensitivity
> > > of dot. This means a "doc-matches-newline" mode (aka "single-line" mode)
> > > where `.' will also match newline. Please see the thread "short regexp to
> > > match any character?" from 2006/03/04 and 03/11.
> > 
> > I don't know any other matcher where dot matches a newline.  Quite
> > more relevant would be inverse character ranges like [^A-Z] that do
> > _not_ match newline by default.
> As far as I remember, Perl regexp syntax has a flag to match or not match
> newline by default.  

Yes, it. It goes like this:


    /.*/        "This"
    /.*/s       Make dot to match (m)ultiline: "This\nLine"

Common modifiers used are:

    i           Case (i)nsensitive match.
    g           (g)lobal match; all occurrances until last one
    m           (m)ultiline achors. The ^ and $ match in between the
                lines, not just at the beginning or end of string. 
    s           Change semantics of "." to also match \r or \n.
    x           e(x)tended. Treat all white space in regexp
                non-significant. Makes it possible to wrire readable
                regular expressions /Like  \s  This/

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