fact: Definition merge {A B C}(f:key->option A->option B->option C) m1 m2 := xmerge (fun k o1 o2 => match o1,o2 with | None,None => None | _, _ => f k o1 o2 end) m1 m2 xH.
imports: Coq(Bool PeanoNat BinPos Orders OrdersEx OrdersLists) MMaps(Utils Comparisons Interface)