fact: Definition charToNibble c : NIBBLE := fromNat (findex 0 (String c EmptyString) "0123456789ABCDEF0123456789abcdef").
imports: Coq(ZArith.ZArith Strings.String) mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq fintype tuple zmodp)