wctypeconst

wctypeconst is a term used in some C library implementations to denote a compile-time constant value of type wctype_t that represents a wide-character classification. It is intended to allow code to refer to a character class without performing a runtime lookup.

In standard C, wide-character classes are obtained at run time by calling wctype with a string name (for example, wctype("alpha") or wctype("space")), which returns a wctype_t value. That value can then be used with iswctype or related functions to test whether a wide character belongs to the class. wctypeconst, when provided by an implementation, aims to supply a precomputed, usable constant of type wctype_t so that constant expressions can be used in contexts that require them.

Availability and portability are important notes. wctypeconst is not part of the ISO C standard, and its presence, exact name, and syntax vary by library and platform. Some implementations may expose predefined constants or provide a different mechanism to obtain a compile-time wctype_t, while others may offer only the runtime wctype() API. developers should consult their compiler's or standard library’s documentation to determine whether wctypeconst or an equivalent feature is available and how to use it correctly.

Commonly supported classification names, when available, include standard categories such as alnum, alpha, digit, space, lower, upper, punct, cntrl, xdigit, graph, print, and more, though the exact set depends on the library. If wctypeconst is not available, code can fall back to using wctype() at runtime or to library-provided constants if the implementation offers them.

See also: wctype, iswctype, wctype_t, wchar.h.