iswctype

iswctype is a function in the C standard library used to test whether a given wide character belongs to a specified character class. It is declared in the header <wctype.h> and works with wide characters represented as wint_t. The function takes two arguments: the wide character wc and a mask of type wctype_t that describes one or more character classes. It returns a nonzero value if wc has any of the properties indicated by the mask, and zero otherwise.

The mask is obtained or constructed through the wctype function, which maps a character class name to a corresponding wctype_t value. Typical class names include "alpha", "digit", "space", "upper", and "lower". A mask may represent a single class or, in some implementations, a combination of classes using bitwise operations on wctype_t values. The exact interpretation of a combined mask is implementation dependent, so users should consult their compiler’s documentation for portable usage.

iswctype is locale-sensitive; the classification of a character depends on the current locale settings. Therefore the same wide character may yield different results in different locales.

Common usage involves testing a wide character against a known class, for example testing whether a character is a decimal digit or an alphabetic letter. A positive result indicates that wc satisfies at least one of the classes encoded in mask.

See also iswalpha, iswalnum, wctype, and setlocale for related means of character classification and locale control.