proposition: Lemma str_le_drop {str n} : drop n str ≤s str.
proof: Proof. destruct n. { rewrite drop_0; reflexivity. } { hnf; rewrite drop_length. case_eq (length str); intro H'. { right; apply bool_eq_empty. { rewrite drop_length, H'; reflexivity. } { assumption. } } { intro; left; omega. } } Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Fiat.Common Fiat.Common.List.Operations Fiat.Common.List.ListFacts Fiat.Common.Le Fiat.Common.Tactics.SetoidSubst Fiat.Common.Tactics.IsClosed Fiat.Parsers.StringLike.Core Fiat.Common.UIP