Commit 2024-12-13 13:44 ddbd4951
View on Github →refactor(Algebra/Category/Ring): make morphisms a structure (#19757)
Following the pattern of #19065, we introduce a Hom structure for morphisms in SemiRingCat, CommSemiRingCat, RingCat and CommRingCat allowing for many simplified proofs and reducing the need of erw.
Besides the additional explicitness in form of ofHom and Hom.hom, the main regression is friction with the FunLike instance from the general ConcreteCategory API, causing the need for explicit rws between f.hom x and (forget RingCat).map f x. This regression can be fixed by replacing the general ConcreteCategory.instFunLike by a CoeFun (or FunLike) instance that is part of the ConcreteCategory data.