Subject: Re: [Boost-users] [regex] why partial match / early break ?
From: John Maddock (boost.regex_at_[hidden])
Date: 2011-11-01 14:15:04
> why is this regex
> const string sRe =
> "((([a-zA-Z]|([a-zA-Z][a-zA-Z0-9\\-]))+[a-zA-Z0-9])\\.)+"
> "((([a-zA-Z]|([a-zA-Z][a-zA-Z0-9\\-]))+[a-zA-Z0-9]))";
>
> not matching this string wholly?
> "a1a.a2a.a3a.a4aaaa"
>
> It rather matches only this part:
> "a1a.a2a.a3a.a4"
>
> What's the problem here?
> (I know I can append a delimiter to solve the problem,
> but I think the regex should've match it wholly, shouldn't it?)
No, in Perl mode, early alternatives are preferred to later ones, so given:
a|aa
against:
aaaa
will only match the first "a".
This is what's happening in your expression.
HTH, John.