Re: [Boost-users] [regex] why partial match / early break ?

Anthony Foiani wrote, On 2011-11-01 19:10:

"U.Mutlu" writes:

...

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"

I think you're getting caught by "first match, not longest match". Put differently, the regex engine isn't backtracking where you think it is.

Thanks for the detailed info, it helped me much.

I'm also curious if you're capturing those substrings for some purpose?

Actually it was my first attempt for writing a "regex for hostnames", because the regex I had found on the web had some bugs. I know there are RFC's for hostname, and that nowadays hostname elements can also start with a digit, but for me a simple (ie. the old) solution suffices.