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.
Related results #
CategoryTheory.Limits.preservesFiniteLimitsOfPreservesEqualizersAndFiniteProducts
: seeCategoryTheory/Limits/Constructions/LimitsOfProductsAndEqualizers.lean
. Also provides the dual version.CategoryTheory.Limits.preservesFiniteLimitsIffFlat
: seeCategoryTheory/Functor/Flat.lean
.
A functor is said to preserve finite limits, if it preserves all limits of shape J
,
where J : Type
is a finite category.
- preservesFiniteLimits : (J : Type) → [inst : CategoryTheory.SmallCategory J] → [inst_1 : CategoryTheory.FinCategory J] → CategoryTheory.Limits.PreservesLimitsOfShape J F
Instances
Preserving finite limits also implies preserving limits over finite shapes in higher universes, though through a noncomputable instance.
If we preserve limits of some arbitrary size, then we preserve all finite limits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
We can always derive PreservesFiniteLimits C
by showing that we are preserving limits at an
arbitrary universe.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The composition of two left exact functors is left exact.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A functor F
preserves finite products if it preserves all from Discrete J
for Fintype J
- preserves : (J : Type) → [inst : Fintype J] → CategoryTheory.Limits.PreservesLimitsOfShape (CategoryTheory.Discrete J) F
Instances
Equations
- CategoryTheory.Limits.compPreservesFiniteProducts F G = { preserves := fun (x : Type) (x_1 : Fintype x) => inferInstance }
Equations
- CategoryTheory.Limits.instPreservesFiniteProductsOfPreservesFiniteLimits F = { preserves := fun (x : Type) (x_1 : Fintype x) => inferInstance }
A functor is said to reflect finite limits, if it reflects all limits of shape J
,
where J : Type
is a finite category.
- reflects : (J : Type) → [inst : CategoryTheory.SmallCategory J] → [inst_1 : CategoryTheory.FinCategory J] → CategoryTheory.Limits.ReflectsLimitsOfShape J F
Instances
A functor F
preserves finite products if it reflects limits of shape Discrete J
for finite J
- reflects : (J : Type) → [inst : Fintype J] → CategoryTheory.Limits.ReflectsLimitsOfShape (CategoryTheory.Discrete J) F
Instances
If we reflect limits of some arbitrary size, then we reflect all finite limits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If F ⋙ G
preserves finite limits and G
reflects finite limits, then F
preserves
finite limits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If F ⋙ G
preserves finite products and G
reflects finite products, then F
preserves
finite products.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- One or more equations did not get rendered due to their size.
Equations
- CategoryTheory.Limits.reflectsFiniteProductsOfReflectsIsomorphisms F = { reflects := fun (x : Type) (x_1 : Fintype x) => CategoryTheory.Limits.reflectsLimitsOfShapeOfReflectsIsomorphisms }
Equations
- CategoryTheory.Limits.compReflectsFiniteProducts F G = { reflects := fun (x : Type) (x_1 : Fintype x) => inferInstance }
Equations
- CategoryTheory.Limits.instReflectsFiniteProductsOfReflectsFiniteLimits F = { reflects := fun (x : Type) (x_1 : Fintype x) => inferInstance }
A functor is said to preserve finite colimits, if it preserves all colimits of
shape J
, where J : Type
is a finite category.
- preservesFiniteColimits : (J : Type) → [inst : CategoryTheory.SmallCategory J] → [inst_1 : CategoryTheory.FinCategory J] → CategoryTheory.Limits.PreservesColimitsOfShape J F
Instances
Preserving finite colimits also implies preserving colimits over finite shapes in higher universes, though through a noncomputable instance.
If we preserve colimits of some arbitrary size, then we preserve all finite colimits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
We can always derive PreservesFiniteColimits C
by showing that we are preserving colimits at an arbitrary universe.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The composition of two right exact functors is right exact.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A functor F
preserves finite products if it preserves all from Discrete J
for Fintype J
- preserves : (J : Type) → [inst : Fintype J] → CategoryTheory.Limits.PreservesColimitsOfShape (CategoryTheory.Discrete J) F
preservation of colimits indexed by
Discrete J
when[Fintype J]
Instances
Equations
- CategoryTheory.Limits.compPreservesFiniteCoproducts F G = { preserves := fun (x : Type) (x_1 : Fintype x) => inferInstance }
Equations
- CategoryTheory.Limits.instPreservesFiniteCoproductsOfPreservesFiniteColimits F = { preserves := fun (x : Type) (x_1 : Fintype x) => inferInstance }
A functor is said to reflect finite colimits, if it reflects all colimits of shape J
,
where J : Type
is a finite category.
- reflects : (J : Type) → [inst : CategoryTheory.SmallCategory J] → [inst_1 : CategoryTheory.FinCategory J] → CategoryTheory.Limits.ReflectsColimitsOfShape J F
Instances
If we reflect colimits of some arbitrary size, then we reflect all finite colimits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
A functor F
preserves finite coproducts if it reflects colimits of shape Discrete J
for
finite J
- reflects : (J : Type) → [inst : Fintype J] → CategoryTheory.Limits.ReflectsColimitsOfShape (CategoryTheory.Discrete J) F
Instances
If F ⋙ G
preserves finite colimits and G
reflects finite colimits, then F
preserves finite
colimits.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If F ⋙ G
preserves finite coproducts and G
reflects finite coproducts, then F
preserves
finite coproducts.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- CategoryTheory.Limits.compReflectsFiniteCoproducts F G = { reflects := fun (x : Type) (x_1 : Fintype x) => inferInstance }
Equations
- CategoryTheory.Limits.instReflectsFiniteCoproductsOfReflectsFiniteColimits F = { reflects := fun (x : Type) (x_1 : Fintype x) => inferInstance }