intuition.
eapply evalDet_steps_done_evalDist_h; eauto.
Qed.
Definition lowDistApprox (A : Set)(c : Comp A)(a : A)(n : nat)(v : Rat) :=
exists vals count,
rel_map (evalDet c) (getAllBlists n) vals /\
pred_count (eq (ca_done a)) vals count  /\
v == (count / expnat 2 n).

Lemma map_Ret_repeat : forall (A : Set)(eqd : eq_dec A)(a : A) ls ls',
rel_map (evalDet (Ret eqd a)) ls ls' ->
ls' = listRepeat (ca_done a) (length ls).