iswdigit

Indicates if a wide character is classed as a digit in the program's current locale.

#include  <wctype.h> (ISO C)

#include  <wchar.h> (XPG4)

int iswdigit  (wint_t wc);

wc: An object of type wint_t. The value of wc must be representable as a wchar_t in the current locale, or must equal the value of the macro WEOF. If it has any other value, the behavior is undefined.

nonzero	If a decimal digit.
0	If not a decimal digit.