proposition: Lemma list_of_string_substring n m str : StringOperations.list_of_string (String.substring n m str) = List.take m (List.drop n (StringOperations.list_of_string str)).
proof: Proof. revert n m; induction str as [|?? IHstr]; intros [|?] [|?]; simpl; rewrite ?IHstr; reflexivity. 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