Section Partition.
Variable f : key -> elt -> bool.
Hypothesis Hf : Proper (E.eq==>eq==>eq) f.
End Partition.

Lemma Partition_Add :
forall m m' x e , ~In x m -> Add x e m m' ->
forall m1 m2, Partition m' m1 m2 ->
exists m3, (Add x e m3 m1 /\ Partition m m3 m2 \/
Add x e m3 m2 /\ Partition m m1 m3).