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Mathlib.CategoryTheory.Limits.Preserves.Finite

Preservation of finite (co)limits. #

These functors are also known as left exact (flat) or right exact functors when the categories involved are abelian, or more generally, finitely (co)complete.

A functor is said to preserve finite limits, if it preserves all limits of shape J, where J : Type is a finite category.

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    If we preserve limits of some arbitrary size, then we preserve all finite limits.

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      We can always derive PreservesFiniteLimits C by showing that we are preserving limits at an arbitrary universe.

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        The composition of two left exact functors is left exact.

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          Transfer preservation of finite limits along a natural isomorphism in the functor.

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            A functor F preserves finite products if it preserves all from Discrete J for Fintype J

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              class CategoryTheory.Limits.ReflectsFiniteLimits {C : Type u₁} [CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [CategoryTheory.Category.{v₂, u₂} D] (F : CategoryTheory.Functor C D) :
              Type (max (max (max (max 1 u₁) u₂) v₁) v₂)

              A functor is said to reflect finite limits, if it reflects all limits of shape J, where J : Type is a finite category.

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                A functor F preserves finite products if it reflects limits of shape Discrete J for finite J

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                  If we reflect limits of some arbitrary size, then we reflect all finite limits.

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                    If F ⋙ G preserves finite limits and G reflects finite limits, then F preserves finite limits.

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                      If F ⋙ G preserves finite products and G reflects finite products, then F preserves finite products.

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                        A functor is said to preserve finite colimits, if it preserves all colimits of shape J, where J : Type is a finite category.

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                          If we preserve colimits of some arbitrary size, then we preserve all finite colimits.

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                            We can always derive PreservesFiniteColimits C by showing that we are preserving colimits at an arbitrary universe.

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                              The composition of two right exact functors is right exact.

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                                Transfer preservation of finite colimits along a natural isomorphism in the functor.

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                                  A functor F preserves finite products if it preserves all from Discrete J for Fintype J

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                                    A functor is said to reflect finite colimits, if it reflects all colimits of shape J, where J : Type is a finite category.

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                                      If we reflect colimits of some arbitrary size, then we reflect all finite colimits.

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                                        A functor F preserves finite coproducts if it reflects colimits of shape Discrete J for finite J

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                                          If F ⋙ G preserves finite colimits and G reflects finite colimits, then F preserves finite colimits.

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                                            If F ⋙ G preserves finite coproducts and G reflects finite coproducts, then F preserves finite coproducts.

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