cpp/locale/ctype char

This specialization of std encapsulates character classification features for type. Unlike general-purpose std, which uses virtual functions, this specialization uses table lookup to classify characters (which is generally faster).

The base class implements character classification equivalent to the minimal "C" locale. The classification rules can be extended or modified if constructed with a non-default classification table argument, if constructed as or as a user-defined derived facet. All std formatted input functions are required to use for character classing during input parsing.