iswxdigit

iswxdigit is a function from the C standard library that tests whether a given wide character represents a hexadecimal digit. It is declared in the header <wchar.h> and has the prototype int iswxdigit(wint_t wc). To use it, include <wchar.h> and pass a wide character value (of type wint_t), such as a wide character literal like L'A' or a value returned by towc.

The function returns a nonzero value if wc is a hexadecimal digit, and zero otherwise. The classification is locale-dependent: in the default C locale, the recognized hex digits are the ASCII characters 0–9, A–F, and a–f. In non-C locales, the set of hex digits may include additional wide characters defined as hexadecimal digits by the current locale’s LC_CTYPE category. As with other wide-character classification functions, the exact behavior for non-ASCII characters depends on the implementation and locale.

Usage and purpose: iswxdigit is used to validate or parse hexadecimal input in programs that process wide-character strings. It serves as the wide-character equivalent of isxdigit for narrow characters and is often used in conjunction with other wide-character classification routines such as iswdigit or iswalpha.

Portability and notes: iswxdigit is part of the standard library interfaces for wide characters and is available on platforms that implement <wchar.h>, including many Unix-like systems and Windows. When writing portable code, be mindful of locale settings, as the result may vary with LC_CTYPE. It expects a wint_t input; passing WEOF is not meaningful for this function. See also isxdigit and iswdigit.