Module Type NZParityProp
(Import A : NZOrdAxiomsSig')
(Import B : NZParity A)
(Import C : NZMulOrderProp A).
(** Morphisms *)
Instance Even_wd : Proper (eq==>iff) Even.
Instance odd_wd : Proper (eq==>Logic.eq) odd.
(** Evenness and oddity are dual notions *)

Lemma double_below : forall n m, n<=m -> 2*n < 2*m+1.