proposition: Lemma find_index: forall (l: list Z) i, 0 <= i < Zlength l -> ~ In (Znth i l) (sublist 0 i l) -> find l (Znth i l) 0 = i.
proof: Proof. intros. replace i with (i + 0) at 2 by lia. apply find_index_gen; trivial. Qed.
imports: VST.floyd.proofauto Coq.Classes.Equivalence CertiGraph.lib.List_ext