cant use math function

*TODO: Return true if input is a digit C'0', '1', '2', '3', '4', '5', '6' *"7', "8', or '9). Return false otherwise. *Hints: ae chars can be compared like ints. and doubles can. For example, you can do * things like 'a' 'b'. Check out http://www.asciitable.com/ to see what *integers different chars map to * a >= b means "a is greater than or equal to b" * a