30 Localization library [localization]

30.4 Standard locale categories [locale.categories]

30.4.2 The ctype category [category.ctype]

30.4.2.1 General [category.ctype.general]

namespace std { class ctype_base { public: using mask = see below; // numeric values are for exposition only. static const mask space = 1 << 0; static const mask print = 1 << 1; static const mask cntrl = 1 << 2; static const mask upper = 1 << 3; static const mask lower = 1 << 4; static const mask alpha = 1 << 5; static const mask digit = 1 << 6; static const mask punct = 1 << 7; static const mask xdigit = 1 << 8; static const mask blank = 1 << 9; static const mask alnum = alpha | digit; static const mask graph = alnum | punct; }; }
The type mask is a bitmask type.