Preservations of limits for bifunctors #
Let G : C₁ ⥤ C₂ ⥤ C a functor. We introduce a class PreservesLimit₂ K₁ K₂ G that encodes
the hypothesis that the curried functor F : C₁ × C₂ ⥤ C preserves limits of the diagram
K₁ × K₂ : J₁ × J₂ ⥤ C₁ × C₂. We give a basic API to extract isomorphisms
$\lim_{(j_1,j_2)} G(K_1(j_1), K_2(j_2)) \simeq G(\lim K_1, \lim K_2)$
out of this typeclass.
Given a bifunctor G : C₁ ⥤ C₂ ⥤ C, diagrams K₁ : J₁ ⥤ C₁ and K₂ : J₂ ⥤ C₂, and cocones
over these diagrams, G.mapCocone₂ c₁ c₂ is the cocone over the diagram J₁ × J₂ ⥤ C obtained
by applying G to both c₁ and c₂.
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Instances For
Given a bifunctor G : C₁ ⥤ C₂ ⥤ C, diagrams K₁ : J₁ ⥤ C₁ and K₂ : J₂ ⥤ C₂, and cones
over these diagrams, G.mapCone₂ c₁ c₂ is the cone over the diagram J₁ × J₂ ⥤ C obtained
by applying G to both c₁ and c₂.
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A functor PreservesColimit₂ K₁ K₂ if whenever c₁ is a colimit cocone and c₂ is a colimit
cocone then G.mapCocone₂ c₁ c₂ is a colimit cocone. This can be thought of as the data of an
isomorphism
$\mathrm{colim}_{(j_1,j_2)} G(K_1(j_1),K_2(j_2)) \simeq G(\mathrm{colim} K_1,\mathrm{colim} K_2)$.
Instances
A functor PreservesLimit₂ K₁ K₂ if whenever c₁ is a limit cone and c₂ is a limit
cone then G.mapCone₂ c₁ c₂ is a limit cone. This can be thought of as the data of an
isomorphism $\lim_{(j_1,j_2)} G(K_1(j_1), K_2(j_2)) \simeq G(\lim K_1, \lim K_2)$.
Instances
If PreservesColimit₂ K₁ K₂ G, obtain that G.mapCocone₂ c₁ c₂ is a colimit cocone
whenever c₁ c₂ are colimit cocones.
Equations
- CategoryTheory.Limits.isColimitOfPreserves₂ G hc₁ hc₂ = ⋯.some
Instances For
If PreservesLimit₂ K₁ K₂ G, obtain that G.mapCone₂ c₁ c₂ is a limit cone
whenever c₁ c₂ are limit cones.
Equations
- CategoryTheory.Limits.isLimitOfPreserves₂ G hc₁ hc₂ = ⋯.some
Instances For
Given a PreservesColimit₂ instance, extract the isomorphism between
a colimit of uncurry.obj (whiskeringLeft₂ C|>.obj K₁|>.obj K₂|>.obj G) and
(G.obj c₁).obj c₂ where c₁ (resp. c₂) is a colimit of K₁ (resp K₂).
Equations
Instances For
Characterize the inverse direction of the isomorphism
PreservesColimit₂.isoObjCoconePointsOfIsColimit w.r.t. the canonical maps to the colimit.
Characterize the forward direction of the isomorphism
PreservesColimit₂.isoObjCoconePointsOfIsColimit w.r.t. the canonical maps to the colimit.
Extract the isomorphism between
colim (uncurry.obj (whiskeringLeft₂ C|>.obj K₁|>.obj K₂|>.obj G)) and
(G.obj (colim K₁)).obj (colim K₂) from a PreservesColimit₂ instance, provided the relevant
colimits exist.
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Characterize the forward direction of the isomorphism
PreservesColimit₂.isoColimitUncurryWhiskeringLeft₂ w.r.t. the canonical maps to the colimit.
Characterize the forward direction of the isomorphism
PreservesColimit₂.isoColimitUncurryWhiskeringLeft₂ w.r.t. the canonical maps to the colimit.
If a bifunctor preserves separately colimits of K₁ in the first variable and colimits
of K₂ in the second variable, then it preserves colimit of the pair K₁, K₂.
Given a PreservesLimit₂ instance, extract the isomorphism between
a limit of uncurry.obj (whiskeringLeft₂ C|>.obj K₁|>.obj K₂|>.obj G) and
(G.obj c₁).obj c₂ where c₁ (resp. c₂) is a limit of K₁ (resp K₂).
Equations
- CategoryTheory.Limits.PreservesLimit₂.isoObjConePointsOfIsLimit G hc₁ hc₂ hc₃ = (CategoryTheory.Limits.isLimitOfPreserves₂ G hc₁ hc₂).conePointUniqueUpToIso hc₃
Instances For
Characterize the forward direction of the isomorphism
PreservesLimit₂.isoObjConePointsOfIsLimit w.r.t. the canonical maps to the limit.
Characterize the inverse direction of the isomorphism
PreservesLimit₂.isoObjConePointsOfIsLimit w.r.t. the canonical maps to the limit.
Extract the isomorphism between
colim (uncurry.obj (whiskeringLeft₂ C|>.obj K₁|>.obj K₂|>.obj G)) and
(G.obj (colim K₁)).obj (colim K₂) from a PreservesLimit₂ instance, provided the relevant
limits exist.
Equations
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Instances For
Characterize the inverse direction of the isomorphism
PreservesLimit₂.isoLimitUncurryWhiskeringLeft₂ w.r.t. the canonical maps to the limit.
Characterize the forward direction of the isomorphism
PreservesLimit₂.isoLimitUncurryWhiskeringLeft₂ w.r.t. the canonical maps to the limit.
If a bifunctor preserves separately limits of K₁ in the first variable and limits
of K₂ in the second variable, then it preserves colimit of the pair of cones K₁, K₂.