fact: Definition retract_is_int_to_ring : IntegersToRing Z2 := λ Z2 _ _ _ _ _, integers_to_ring Z Z2 ∘ f⁻¹.
imports: Coq.setoid_ring.Ring MathClasses.interfaces.naturals MathClasses.interfaces.abstract_algebra MathClasses.implementations.natpair_integers MathClasses.interfaces.integers