Re: RFC 72 (v2) The regexp engine should go backward as well as forward.

From: "Peter Heslin" <[email protected]>
Sent: Thursday, August 31, 2000 10:51 PM

> I would propose that your version of the syntax might also function in
> the middle of a regexp: /GHI(?`<=DEF)JKL(?`<=^ABC)MNO/ would match the
> start of the alphabet (fixed-length example used for simplicity).

That's not what I had in mind; I would have the new look-behind look (in
terms of left-to-right placement) and act like the existing (?<=pat), except
that it would have non-zero width and create a back-reference.

The example above would (if we remove the ^ ) match GHIDEFJKLABCMNO

Hmm, that non-zero width thing is screwy.  The zero-width analog,
/GHI(?<=DEF)JKL(?<=^ABC)MNO/, would NEVER match.  That asks for a GHI
immediately followed by a JKL immediately preceeded by a DEF.

Without some better motivating examples, I'd rather keep the old and
proposed look-behinds working the same.  So let me retract what I said above
about matching GHIDEFJKLABCMNO  A match would be had with
/GHI.*(?`<=DEF)JKL.*(?`<=ABC)MNO/

  mike mulligan