Proof with auto with arith.
subst qs. unfold U.qs.
intro.
pattern l, (qs_definitions.mon_nondet.qs (U.cmp (e:=ee) (ol:=ol)) U.pick l).
apply U.qs_ind.
simpl.
intros r H.
inversion_clear H.
simpl.
intros.
elimtype False...
intros.
cset (NeTree_In_Node_inv H0). clear H0.
destruct (ne_tree.InL_map_inv _ _ H3). clear H3. destruct H0.
destruct (ne_tree.In_map_inv _ _ H0). clear H0. destruct H4.
subst r.
unfold monoid_expec.map_fst in H2.
unfold fst in H2.
destruct (in_app_or _ _ _ H2); clear H2.
destruct (In_map_inv H0). clear H0. destruct H2.
unfold U.unordered_nat_pair in H0.
destruct (le_lt_dec x1 (vec.nth v x)); destruct (pair_eq_inv H0)...
subst.
apply ne_le_impl_lt...
intro.
rewrite (vec.List_Permutation (vec.perm_sym (vec.remove_perm x v))) in H1.
inversion_clear H1.
apply H6.
cset(natBelow_unique _ _ H5).
subst x1...
subst...
destruct (ne_tree_monad.In_bind_inv _ _ H4). clear H4. destruct H2.
unfold U.M in H4.
rewrite MonoidMonadTrans.bind_toLower in H4.
rewrite (@mon_assoc ne_tree_monad.M ) in H4.
destruct (ne_tree_monad.In_bind_inv _ _ H4). clear H4. destruct H5.
revert H0.
rewrite (@mon_assoc ne_tree_monad.M) in H5.
rewrite MonoidMonadTrans.ret_toLower in H5.
rewrite (@mon_lunit ne_tree_monad.M) in H5.
simpl @fst in H5.
rewrite (@mon_lunit ne_tree_monad.M) in H5.
simpl @fst in H5.
unfold snd in H5.
inversion_clear H5.
simpl.
rewrite app_nil_r.
intros.
assert (forall cr, NoDup (filter (fun f: Index ee ol => unsum_bool (cmp_cmp (Ecmp ee (subscript f) (subscript (vec.nth v x))) cr)) (vec.remove v x))).
intros.
apply NoDup_SkipList with v...
apply SkipList_trans with (vec.remove v x).
apply SkipList_filter.
apply vec.SkipList_remove.
assert (forall k cr, IndexIn k (filter (fun f: Index ee ol => unsum_bool (cmp_cmp (Ecmp ee (subscript f) (subscript (vec.nth v x))) cr)) (vec.remove v x)) -> IndexIn k v).
intros.
unfold IndexIn in *.
apply (incl_In _ H6).
apply incl_map.
apply incl_trans with (vec.remove v x)...
apply SkipList_incl.
apply vec.SkipList_remove.
destruct (in_app_or _ _ _ H0).
apply H with x Lt x1...
apply H with x Gt x2...
Qed.

Lemma sound_cmp_expec_0 i j (l: list (Index ee ol)):
(~ In i l \/ ~ In j l) -> monoid_expec (U.ijcount i j) (qs l) = 0.