Re: [boost] Re: [Regex patch] compiling on Mac OSX with gcc 2.95

From: John Maddock (boost.regex_at_[hidden])
Date: 2003-10-10 06:23:05

> Incidentally, do you have any idea about what I'm doing wrong with
> match_partial
> http://article.gmane.org/gmane.comp.lib.boost.user/4569
>
> (Ok, I know that was sly ;-)

No problem, for some reason that one hasn't shown up in my inbox, anyway:

>I'm afraid I haven't got the hang of match_partial.
>
>Below is a little code with two functions that I think should produce
>identical results, but don't.
>
>In strip_commas_try1 I use:
>        boost::regex const front("^( *[[],*)(.*)$");
>        regex_match(it, end, what, front);
>In strip_commas_try2 I use:
>        boost::regex const front("^( *[[],*)");
>        regex_match(it, end, what, front, boost::match_partial);
>
>Why does this second case not result in
>        what[0].matched

There are two errors in your code:

1) you should check the return value of regex_match to see if there is some
kind of match before checking what[0].matched to see if it was partial or
not.
2) The second match fails because you called regex_match and the expression
cannot match *all* of the text.  If you want to match *some* of the text
then use regex_search.  The match_partial flag will only come into play if
all of the text is matched, but not all of the expression.

John.