Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Global alpha

boost::xpressive::alpha — Matches an alphabetic character.

// In header: <boost/xpressive/regex_primitives.hpp>

unspecified alpha;

The regex traits are used to determine which characters are alphabetic. To match any character that is not alphabetic, use ~alpha.

	Note
	alpha is equivalent to /[[:alpha:]]/ in perl. ~alpha is equivalent to /[[:^alpha:]]/ in perl.