Section MapDisjointExtra.
Variables A B : Type.

Lemma MapMerge_disjoint :
forall m m':Map A,
MapDisjoint A A m m' ->
forall a:ad,
in_dom A a (MapMerge A m m') =
orb (andb (in_dom A a m) (negb (in_dom A a m')))
(andb (in_dom A a m') (negb (in_dom A a m))).