Module ZMulProp (Import Z : ZAxiomsMiniSig').
Include ZAddProp Z.
(** A note on naming: right (correspondingly, left) distributivity happens when the sum is multiplied by a number on the right (left), not when the sum itself is the right (left) factor in the product (see planetmath.org and mathworld.wolfram.com). In the old library BinInt, distributivity over subtraction was named correctly, but distributivity over addition was named incorrectly. The names in Isabelle/HOL library are also incorrect. *)
(** Theorems that are either not valid on N or have different proofs on N and Z *)

Theorem mul_opp_opp : forall n m, (- n) * (- m) == n * m.