Section Monotonicity.
Variables (leT' : rel T') (leT : rel T).
Hypothesis f_mono : {mono f : x y / leT' x y >-> leT x y}.
End Monotonicity.
Variable leT : rel T.

Lemma merge_map s1 s2 :
merge leT (map f s1) (map f s2) = map f (merge (relpre f leT) s1 s2).