cpp/string/byte/isalnum

Checks if the given character is an alphanumeric character as classified by the current C locale. In the default locale, the following characters are alphanumeric:


 * digits
 * uppercase letters
 * lowercase letters

The behavior is undefined if the value of is not representable as  and is not equal to.

Return value
Non-zero value if the character is an alphanumeric character, otherwise.