The category of abelian groups has finite biproducts

instance AddCommGrp.instHasBinaryBiproducts : CategoryTheory.Limits.HasBinaryBiproducts AddCommGrp

instance AddCommGrp.instHasFiniteBiproducts : CategoryTheory.Limits.HasFiniteBiproducts AddCommGrp

def AddCommGrp.binaryProductLimitCone (G H : AddCommGrp) : CategoryTheory.Limits.LimitCone (CategoryTheory.Limits.pair G H)

Construct limit data for a binary product in AddCommGrp, using AddCommGrp.of (G × H).

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem AddCommGrp.binaryProductLimitCone_isLimit_lift (G H : AddCommGrp) (s : CategoryTheory.Limits.Cone (CategoryTheory.Limits.pair G H)) : (G.binaryProductLimitCone H).isLimit.lift s = AddMonoidHom.prod (s.π.app { as := CategoryTheory.Limits.WalkingPair.left }) (s.π.app { as := CategoryTheory.Limits.WalkingPair.right })

@[simp]

theorem AddCommGrp.binaryProductLimitCone_cone_pt (G H : AddCommGrp) : (G.binaryProductLimitCone H).cone.pt = AddCommGrp.of (↑G × ↑H)

@[simp]

theorem AddCommGrp.binaryProductLimitCone_cone_π_app_left (G H : AddCommGrp) : (G.binaryProductLimitCone H).cone.π.app { as := CategoryTheory.Limits.WalkingPair.left } = AddMonoidHom.fst ↑G ↑H

@[simp]

theorem AddCommGrp.binaryProductLimitCone_cone_π_app_right (G H : AddCommGrp) : (G.binaryProductLimitCone H).cone.π.app { as := CategoryTheory.Limits.WalkingPair.right } = AddMonoidHom.snd ↑G ↑H

noncomputable def AddCommGrp.biprodIsoProd (G H : AddCommGrp) : G ⊞ H ≅ AddCommGrp.of (↑G × ↑H)

We verify that the biproduct in AddCommGrp is isomorphic to the cartesian product of the underlying types:

Equations

• G.biprodIsoProd H = (CategoryTheory.Limits.BinaryBiproduct.isLimit G H).conePointUniqueUpToIso (G.binaryProductLimitCone H).isLimit

@[simp]

theorem AddCommGrp.biprodIsoProd_inv_comp_fst (G H : AddCommGrp) : CategoryTheory.CategoryStruct.comp (G.biprodIsoProd H).inv CategoryTheory.Limits.biprod.fst = AddMonoidHom.fst ↑G ↑H

theorem AddCommGrp.biprodIsoProd_inv_comp_fst_apply (G H : AddCommGrp) (x : (CategoryTheory.forget AddCommGrp).obj (AddCommGrp.of (↑G × ↑H))) : CategoryTheory.Limits.biprod.fst ((G.biprodIsoProd H).inv x) = (AddMonoidHom.fst ↑G ↑H) x

@[simp]

theorem AddCommGrp.biprodIsoProd_inv_comp_snd (G H : AddCommGrp) : CategoryTheory.CategoryStruct.comp (G.biprodIsoProd H).inv CategoryTheory.Limits.biprod.snd = AddMonoidHom.snd ↑G ↑H

theorem AddCommGrp.biprodIsoProd_inv_comp_snd_apply (G H : AddCommGrp) (x : (CategoryTheory.forget AddCommGrp).obj (AddCommGrp.of (↑G × ↑H))) : CategoryTheory.Limits.biprod.snd ((G.biprodIsoProd H).inv x) = (AddMonoidHom.snd ↑G ↑H) x

def AddCommGrp.HasLimit.lift {J : Type w} (f : J → AddCommGrp) (s : CategoryTheory.Limits.Fan f) : s.pt ⟶ AddCommGrp.of ((j : J) → ↑(f j))

The map from an arbitrary cone over an indexed family of abelian groups to the cartesian product of those groups.

Equations

• AddCommGrp.HasLimit.lift f s = { toFun := fun (x : ↑s.pt) (j : J) => (s.π.app { as := j }) x, map_zero' := ⋯, map_add' := ⋯ }

def AddCommGrp.HasLimit.productLimitCone {J : Type w} (f : J → AddCommGrp) : CategoryTheory.Limits.LimitCone (CategoryTheory.Discrete.functor f)

Construct limit data for a product in AddCommGrp, using AddCommGrp.of (∀ j, F.obj j).

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem AddCommGrp.HasLimit.productLimitCone_isLimit_lift {J : Type w} (f : J → AddCommGrp) (s : CategoryTheory.Limits.Fan f) : (AddCommGrp.HasLimit.productLimitCone f).isLimit.lift s = AddCommGrp.HasLimit.lift f s

@[simp]

theorem AddCommGrp.HasLimit.productLimitCone_cone_π {J : Type w} (f : J → AddCommGrp) : (AddCommGrp.HasLimit.productLimitCone f).cone.π = CategoryTheory.Discrete.natTrans fun (j : CategoryTheory.Discrete J) => Pi.evalAddMonoidHom (fun (j : J) => ↑(f j)) j.as

@[simp]

theorem AddCommGrp.HasLimit.productLimitCone_cone_pt {J : Type w} (f : J → AddCommGrp) : (AddCommGrp.HasLimit.productLimitCone f).cone.pt = AddCommGrp.of ((j : J) → ↑(f j))

noncomputable def AddCommGrp.biproductIsoPi {J : Type} [Finite J] (f : J → AddCommGrp) : ⨁ f ≅ AddCommGrp.of ((j : J) → ↑(f j))

We verify that the biproduct we've just defined is isomorphic to the AddCommGrp structure on the dependent function type.

Equations

• AddCommGrp.biproductIsoPi f = (CategoryTheory.Limits.biproduct.isLimit f).conePointUniqueUpToIso (AddCommGrp.HasLimit.productLimitCone f).isLimit

@[simp]

theorem AddCommGrp.biproductIsoPi_inv_comp_π {J : Type} [Finite J] (f : J → AddCommGrp) (j : J) : CategoryTheory.CategoryStruct.comp (AddCommGrp.biproductIsoPi f).inv (CategoryTheory.Limits.biproduct.π f j) = Pi.evalAddMonoidHom (fun (j : J) => ↑(f j)) j

theorem AddCommGrp.biproductIsoPi_inv_comp_π_apply {J : Type} [Finite J] (f : J → AddCommGrp) (j : J) (x : (CategoryTheory.forget AddCommGrp).obj (AddCommGrp.of ((j : J) → ↑(f j)))) : (CategoryTheory.Limits.biproduct.π f j) ((AddCommGrp.biproductIsoPi f).inv x) = (Pi.evalAddMonoidHom (fun (j : J) => ↑(f j)) j) x