proposition: Lemma length_drop {A} (n : nat) (ls : list A) : List.length (List.drop n ls) = List.length ls - n.
proof: Proof. revert ls; induction n; simpl; intros. { auto with arith. } { destruct ls; simpl; [ reflexivity | ]. apply IHn. } Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts