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 constexpr mask space = 1 << 0; static constexpr mask print = 1 << 1; static constexpr mask cntrl = 1 << 2; static constexpr mask upper = 1 << 3; static constexpr mask lower = 1 << 4; static constexpr mask alpha = 1 << 5; static constexpr mask digit = 1 << 6; static constexpr mask punct = 1 << 7; static constexpr mask xdigit = 1 << 8; static constexpr mask blank = 1 << 9; static constexpr mask alnum = alpha | digit; static constexpr mask graph = alnum | punct; }; }
The type mask is a bitmask type.