iswdigit function — Determines whether a wide character is a digit
int iswdigit(wint_t wc)
The iswdigit function returns true (nonzero) if wc is a decimal digit character—that is, '0'-'9'—regardless of locale.
iswdigit
wc
0
9
iswxdigit function, isdigit in <cctype>
isdigit
<cctype>