proposition: Lemma Eqdom_cardinal m m' : Eqdom m m' -> cardinal m = cardinal m'.
proof: Proof. intro. rewrite 2 cardinal_foldkeys. apply foldkeys_Proper with (eqA:=eq); try congruence; auto with map. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)