Cartesian products of categories #
We define the category instance on C × D when C and D are categories.
We define:
sectL C Z: the functorC ⥤ C × Dgiven byX ↦ ⟨X, Z⟩sectR Z D: the functorD ⥤ C × Dgiven byY ↦ ⟨Z, Y⟩fst: the functor⟨X, Y⟩ ↦ Xsnd: the functor⟨X, Y⟩ ↦ Yswap: the functorC × D ⥤ D × Cgiven by⟨X, Y⟩ ↦ ⟨Y, X⟩(and the fact that this is an equivalence)
We further define evaluation : C ⥤ (C ⥤ D) ⥤ D and evaluationUncurried : C × (C ⥤ D) ⥤ D,
and products of functors and natural transformations, written F.prod G and α.prod β.
CategoryStruct.prod C D gives the Cartesian product of two CategoryStruct's.
Construct a morphism in a product category by giving its constituent components.
This constructor should be preferred over Prod.mk, because Lean infers better the
source and target of the resulting morphism.
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Construct a morphism in a product category by giving its constituent components.
This constructor should be preferred over Prod.mk, because Lean infers better the
source and target of the resulting morphism.
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Analogue of Prod.mk.injEq in this setting.
prod C D gives the Cartesian product of two categories.
The isomorphism between (X.1, X.2) and X.
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Construct an isomorphism in C × D out of two isomorphisms in C and D.
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Category.uniformProd C D is an additional instance specialised so both factors have the same
universe levels. This helps typeclass resolution.
sectL C Z is the functor C ⥤ C × D given by X ↦ (X, Z).
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sectR Z D is the functor D ⥤ C × D given by Y ↦ (Z, Y) .
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fst is the functor (X, Y) ↦ X.
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snd is the functor (X, Y) ↦ Y.
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The functor swapping the factors of a Cartesian product of categories, C × D ⥤ D × C.
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Swapping the factors of a Cartesian product of categories twice is naturally isomorphic to the identity functor.
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The equivalence, given by swapping factors, between C × D and D × C.
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Any morphism in a product factors as a morphism whose left component is an identity followed by a morphism whose right component is an identity.
Any morphism in a product factors as a morphism whose left component is an identity followed by a morphism whose right component is an identity.
Any morphism in a product factors as a morphism whose right component is an identity followed by a morphism whose left component is an identity.
Any morphism in a product factors as a morphism whose right component is an identity followed by a morphism whose left component is an identity.
The "evaluation at X" functor, such that
(evaluation.obj X).obj F = F.obj X,
which is functorial in both X and F.
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The "evaluation of F at X" functor,
as a functor C × (C ⥤ D) ⥤ D.
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The constant functor followed by the evaluation functor is just the identity.
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The Cartesian product of two functors.
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Similar to prod, but both functors start from the same category A
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The product F.prod' G followed by projection on the first component is isomorphic to F
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The product F.prod' G followed by projection on the second component is isomorphic to G
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The diagonal functor.
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The Cartesian product of two natural transformations.
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The Cartesian product of two natural transformations where both functors have the same source.
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The Cartesian product functor between functor categories
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The Cartesian product of two natural isomorphisms.
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The Cartesian product of two equivalences of categories.
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F.flip composed with evaluation is the same as evaluating F.
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F composed with evaluation is the same as evaluating F.flip.
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Whiskering by F and then evaluating at a is the same as evaluating at F.obj a.
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Whiskering by F and then evaluating at a is the same as evaluating at F.obj a.
Whiskering by F and then evaluating at a is the same as evaluating at F and then
applying F.
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Whiskering by F and then evaluating at a is the same as evaluating at F and then
applying F.
The forward direction for functorProdFunctorEquiv
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The backward direction for functorProdFunctorEquiv
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The unit isomorphism for functorProdFunctorEquiv
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The counit isomorphism for functorProdFunctorEquiv
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The equivalence of categories between (A ⥤ B) × (A ⥤ C) and A ⥤ (B × C)
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The equivalence between the opposite of a product and the product of the opposites.