Boost C++ Libraries: Ticket #679: regex - perl syntax affects what gets matched

nobody — Mon, 10 Jul 2006 09:03:32 GMT

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If you use the Perl syntax then you now get Perl matching
rules.  You can pass match_posix to the matching algorithms
to force them to use leftmost-longest, but the behaviour is
very hard to specify for Perl-expressions.  Or you can
compile the expression as a POSIX regex using
regex::extended or regex::basic and then get well-defined
leftmost longest behaviour with POSIX compatible expressions.
The problem is that mixing Perl syntax and leftmost longest
rules leads to all kinds of problems when you try and figure
out what a "non-greedy-repeat" should do for example.  There
are similar issues with other Perl extensions.
HTH, John.

nobody — Mon, 24 Jul 2006 11:14:36 GMT

Logged In: NO
Thanks. I'll try that.
I'm still left with one question:
Where are the flags "match_posix" and "no_perl_ex" appear
documentated?
Thanks, Moddy.

component changed; severity set

Daryle Walker — Fri, 03 Aug 2007 12:11:22 GMT

component None → regex
severity → Problem

status, resolution, description changed

John Maddock — Mon, 13 Aug 2007 17:48:15 GMT

status assigned → closed
resolution None → fixed
description modified (diff)

Sorry for the delay: no_perl_ex is intended for internal use and intentionally not documented. The new match_flag_type options I've just added to the docs in SVN now.