intros.
induction l.
auto.
simpl.
rewrite insert_reorder. rewrite IHl. auto.
Qed.
rewrite insert_insertion_sort. cancel.
unfold body_post.
forward_intro sorted_list.
forward.
apply exp_right with sorted.
entailer!.
Qed.

(* Specifications: *)
Lemma body_insert: semax_body Vprog Gprog f_insert insert_spec.
apply insert_value_right in H1. subst. rewrite H1.