proposition: Lemma Forall3_app_inv_l l1 l2 k k' : Forall3 P (l1 ++ l2) k k' → ∃ k1 k2 k1' k2', k = k1 ++ k2 ∧ k' = k1' ++ k2' ∧ Forall3 P l1 k1 k1' ∧ Forall3 P l2 k2 k2'.
proof: Proof. revert k k'. induction l1 as [|x l1 IH]; simpl; inv 1. - by repeat eexists; eauto. - by repeat eexists; eauto. - edestruct IH as (?&?&?&?&?&?&?&?); eauto; naive_solver. Qed.
imports: stdpp(options)