Proof with auto.
intros.
pose proof (vec.length t).
rewrite H in H0.
rewrite vec.length in H0.
inversion H0.
subst. clear H0.
rewrite (vec.eq_as_lists t t')...
Qed.
Definition body n (v: Vector.t X n) :=
match v with
| Vector.nil => ret nil
| l => selectPivotPart l
end.
Definition raw_body (l0: list X) (qs: {l': list X | length l' < length l0} -> M (list X)) :=
match l0 as l1 return (l1 = l0 -> M (list X)) with
| nil => fun _ => ret nil
| h :: t => fun e =>
i <- pick (ne_list.from_vec (vec.nats 0 (length (h :: t))));
part <- partition M cmp (vec.nth (h :: t) i) (vec.remove (h :: t) i);
low <- qs (exist (fun l': list X => length l' < length l0) (proj1_sig part Lt) (qs_definitions.mon_nondet.qs_obligation_1 M (fun l H => qs (exist _ l H)) e i part));
upp <- qs (exist (fun l': list X => length l' < length l0) (proj1_sig part Gt) (qs_definitions.mon_nondet.qs_obligation_2 M (fun l H => qs (exist _ l H)) e i part));
ret (low ++ vec.nth (h :: t) i :: proj1_sig part Eq ++ upp)
end refl_equal.
Variable e: extMonad M.
Definition raw_body_ext (l: list X) (qs qs': {l': list X | length l' < length l} -> M (list X)):
(forall x y, proj1_sig x = proj1_sig y -> qs x = qs' y) -> raw_body l qs = raw_body l qs'.
Proof with auto.
unfold raw_body.
intros.
destruct l...
apply e. intro.
apply e. intro.
apply bind_eqq...
intro.
apply bind_eqq...
intro...
Qed.

Lemma bodies x0:
raw_body x0 (fun y: {y: list X | length y < length x0} => qs (M:=M) cmp pick (proj1_sig y)) = body x0.