unfold extMonad.
induction x using ne_tree.alt_ind; simpl...
replace (ne_list.map (fun x: C A => bind x f) l) with (ne_list.map (fun x: C A => bind x g) l)...
generalize H0. clear H0.
induction l; simpl; intros; rewrite H0...
rewrite IHl...
Qed.

Lemma deterministic_ret (A: Set) (a: A): deterministic (ret a) a.