proposition: Lemma substring_correct0 {s : string} {n} : substring n 0 s = ""%string.
proof: Proof. revert n; induction s; intro n; destruct n; simpl; trivial. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Arith.PeanoNat Coq.Strings.Ascii Coq.Strings.String Fiat.Common.List.Operations Fiat.Common.StringOperations