induction c; intuition; simpl in *.
inversion H; clear H; subst.
trivial.
case_eq (evalDet_step c nil); intuition;
rewrite H1 in H0;
try discriminate.
destruct n; simpl.
discriminate.
discriminate.
discriminate.
Qed.

Lemma lowDistApprox_low : forall (A : Set)(c : Comp A),
well_formed_comp c ->
forall n a r,
lowDistApprox c a n r ->
r <= evalDist c a.