`skipN` function.

_CoqProject

 -Q theories actris
 -arg -w -arg -notation-overridden,-redundant-canonical-projection,-several-object-files,-convert_concl_no_check,-undeclared-scope,-ambiguous-paths
+theories/utils/skip.v
 theories/utils/llist.v
 theories/utils/compare.v
 theories/utils/contribution.v

theories/utils/skip.v

+From iris.heap_lang Require Export lang.
+From iris.heap_lang Require Import proofmode notation.
+
+Definition skipN : val :=
+  rec: "go" "n" := if: #0 < "n" then "go" ("n" - #1) else #().
+
+Lemma skipN_spec `{heapG Σ} Φ (n : nat) : ▷^n (Φ #()) -∗ WP skipN #n {{ Φ }}.
+Proof.
+  iIntros "HΦ". iInduction n as [|n] "IH"; wp_rec; wp_pures; [done|].
+  rewrite Z.sub_1_r Nat2Z.inj_succ Z.pred_succ. by iApply "IH".
+Qed.