Section contents.
Variables (ee: E) (ol: list ee) (i j: Index ee ol).
Variable n: nat.
Variable v: Vector.t (Index ee ol) (S n).
Variable iltj: (i < j)%nat.
Let flt x0 cr := filter (fun f: Index ee ol => unsum_bool (cmp_cmp (Ecmp (UE ee ol) f (vec.nth v x0)) cr)) (vec.to_list (vec.remove v x0)).
Variable IH: forall (x0: natBelow (S n)) (cr: comparison) (b: nat),
IndexSeq b (flt x0 cr) ->
monoid_expec (U.ijcount i j) (qs (U.cmp (e:=ee) (ol:=ol)) U.pick (flt x0 cr)) <= 2 / INR (S (j - i)).
Variables (b: nat) (is: IndexSeq b (vec.to_list v)).
apply IndexSeq_NoDup with b.
assumption.
Qed.
Variable iin: In i (vec.to_list v).
Variable jin: In j (vec.to_list v).
Variable pi: natBelow (S n).
Proof with auto.
unfold flt.
intros.
intro.
destruct (proj1_conj (filter_In _ _ _) H). clear H.
simpl in H0.
simpl in H2.
destruct (Ecmp ee (subscript k) (subscript (vec.nth v pi))); destruct dr; auto; simpl in H2; try discriminate...
Qed.
Hint Immediate ndi_flt.
Hint Immediate U.hom_ijcount.
Hint Immediate vec.remove_perm.

Lemma pivot_not_In_flt cr: ~ In (vec.nth v pi) (flt pi cr).