proposition: Lemma substring_correct3 {s : string} m (H : length s <= m) : substring 0 m s = s.
proof: Proof. revert m H. induction s; simpl. { intros; destruct m; trivial. } { intros; destruct m. { apply Nat.nlt_0_r in H. destruct H. } { rewrite IHs; trivial. apply Nat.succ_le_mono; 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