intuition.
eapply refl.
eapply evalDist_commute_eq.
Qed.

Lemma rel_sumList_compat :
forall (A : Set)(f1 f2 : A -> Rat) ls rel,
RatRel rel ->
(forall a, In a ls -> rel (f1 a) (f2 a)) ->
rel (sumList ls f1) (sumList ls f2).