fact: Definition isAlpha (c : ascii) : bool := let n := nat_of_ascii c in orb (andb (65 <=? n) (n <=? 90)) (andb (97 <=? n) (n <=? 122)).
imports: Coq.Strings.String Coq.Strings.Ascii Coq.Arith.Arith Coq.Arith.EqNat Coq.Lists.List Maps Imp