proposition: Lemma eq_empty (m: t elt) : m == empty <-> is_empty m = true.
proof: Proof. unfold Equal. rewrite is_empty_spec. now setoid_rewrite empty_spec. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)