fact: Definition cring_catamorphism_fun (R : CRing) (z : cring_Z) : R := match z with | neg z => pos_peano_rec R (-1) (fun n nr => -1 + nr) z | 0%int => 0 | pos z => pos_peano_rec R 1 (fun n nr => 1 + nr) z end.
imports: Classes.interfaces.abstract_algebra Algebra.AbGroups Algebra.Rings.CRing Spaces.Int Spaces.Pos WildCat.Core