Re: [Boost-users] Regex failure

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-02-05 19:50:11

Bob Kline wrote:

> #include <boost/regex.hpp>
> int main() {
>    boost::wregex  e(L"^[^\\s]( ?([^\\s]+ ?)*[^\\s])?$");
>    boost::wcmatch m;
>    boost::regex_match(L"codeine phosphate ", m, e);
>    return 0;
> }

[...]

> I'm pretty sure that the expression is boiled down to the least
> ambiguous form (without changing the semantics).  In plain English,
> it's looking for strings that have no leading or trailing whitespace,
> and for which any internal whitespace runs are comprised solely of a
> single blank character.

I've no idea which part of the regexp causes the library to give up, but 
isn't there a much simpler reformulation:

  ^[^\s]+( [^\s]+)*$

that achieves the same result? In addition to running at all, it should also 
run much faster. :-) Unless I've missed something, of course.