hex()
Treats leading characters from str as a string of hexadecimal digits (with an optional sign and an optional 0x) and returns the corresponding number. Zero is returned on error.
"0x0a".hex #=> 10 "-1234".hex #=> -4660 "0".hex #=> 0 "wombat".hex #=> 0
static VALUE rb_str_hex(VALUE str) { return rb_str_to_inum(str, 16, FALSE); }