proposition: Lemma decides_length_firstn_skipn_app {A} : forall (n m o : nat) (l : list A), length l = n + (m + o) -> decides true (length (firstn m (skipn n l) ) = m).
proof: Proof. intros. rewrite length_firstn_skipn_app with (o0 := o); simpl; omega. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.Bool.Bool Coq.ZArith.ZArith Coq.Lists.List Fiat.Common.DecideableEnsembles Fiat.Common.EnumType Fiat.Common.BoundedLookup Fiat.Common Fiat.Common.ilist Fiat.Common.Tactics.CacheStringConstant Fiat.Common.IterateBoundedIndex Fiat.Computation Bedrock.Word