proposition: Lemma is_empty_bindings m : is_empty m = true <-> bindings m = nil.
proof: Proof. rewrite <- is_empty_iff, cardinal_Empty, cardinal_spec. now destruct bindings. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)