WCtype

wctype is a function in the C standard library, declared in the header <wctype.h>, that provides runtime lookup of wide-character classification properties. It maps a character class name, supplied as a string, to a corresponding classification mask of type wctype_t. This mask can then be used with the iswctype function to test whether a given wide character belongs to that class.

The signature is: wctype_t wctype(const char *name); The function returns a nonzero mask when the name is recognized, or 0 if the name is not recognized. The actual meaning of the returned mask depends on the current LC_CTYPE locale, so classification can vary with locale settings. Names commonly recognized include "alpha", "digit", "space", "upper", "lower", "xdigit", "print", and "punct", among others defined by the standard and extended by implementations.

Usage typically involves obtaining a mask once and applying it to multiple wide characters via iswctype. For example, wctype_t m = wctype("digit"); if (iswctype(ch, m)) { /* ch is a decimal digit */ } A more general form is to test a wide character directly with a specified class: iswctype(L'A', wctype("alpha")) returns true if the character is alphabetic. The wctype mechanism is useful when the set of character classes is determined at runtime or when writing portable code that relies on locale-specific character properties rather than hard-coded constants.

Portability notes: Not all environments implement every class name, and the exact set of names is locale-dependent. If wctype returns 0, the requested property is not available in the current locale or implementation. For basic classification, traditional iswalpha, iswdigit, and related functions remain available and often more straightforward.