proposition: Lemma cvmgil_not_eq: forall to n l, n <> to -> to < length l -> nth n (copy_v_mod_gen_info_list l to) null_info = nth n l null_info.
proof: Proof. intros. unfold copy_v_mod_gen_info_list. assert (length (firstn to l) = to) by (rewrite firstn_length_le; lia). destruct (Nat.lt_ge_cases n to). - rewrite app_nth1 by lia. apply nth_firstn. assumption. - rewrite Nat.lt_eq_cases in H2. destruct H2. 2: exfalso; intuition auto. rewrite <- (firstn_skipn (to + 1) l) at 4. rewrite app_cons_assoc, !app_nth2. + do 2 f_equal. rewrite app_length, H1, firstn_length_le by lia. reflexivity. + rewrite firstn_length_le; lia. + rewrite app_length, H1. simpl. lia. Qed.
imports: Coq.ZArith.ZArith Coq.Program.Basics Coq.micromega.Lia compcert.lib.Integers compcert.common.Values VST.veric.base VST.veric.Clight_lemmas VST.veric.val_lemmas VST.veric.shares VST.msl.seplog VST.msl.shares VST.zlist.sublist VST.floyd.coqlib3 VST.floyd.functional_base VST.floyd.data_at_rec_lemmas VST.zlist.list_solver CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_gen