proposition: Lemma substring_concat0 {s1 s2 : string} : substring 0 (length s1) (s1 ++ s2) = s1.
proof: Proof. induction s1; simpl. { rewrite substring_correct0; trivial. } { rewrite IHs1; 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