Morphisms of categorical cospans. #
Given F : A ⥤ B, G : C ⥤ B, F' : A' ⥤ B' and G' : C' ⥤ B',
this file defines CatCospanTransform F G F' G', the category of
"categorical transformations" from the (categorical) cospan F G to
the (categorical) cospan F' G'. Such a transformation consists of a
diagram
F G
A ⥤ B ⥢ C
H₁| |H₂ |H₃
v v v
A'⥤ B'⥢ C'
F' G'
with specified CatCommSqs expressing 2-commutativity of the squares. These
transformations are used to encode 2-functoriality of categorical pullback squares.
A CatCospanTransform F G F' G' is a diagram
F G
A ⥤ B ⥢ C
H₁| |H₂ |H₃
v v v
A'⥤ B'⥢ C'
F' G'
with specified CatCommSqs expressing 2-commutativity of the squares.
- left : Functor A A'
the functor on the left component
- base : Functor B B'
the functor on the base component
- right : Functor C C'
the functor on the right component
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The identity CatCospanTransform
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Composition of CatCospanTransforms is defined "componentwise".
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A morphism of CatCospanTransform F G F' G' is a triple of natural
transformations between the component functors, subjects to
coherence conditions respective to the squares.
the natural transformations between the left components
the natural transformations between the right components
the natural transformations between the base components
- left_coherence : CategoryStruct.comp (CatCommSq.iso F ψ.left ψ.base F').hom (Functor.whiskerRight self.left F') = CategoryStruct.comp (F.whiskerLeft self.base) (CatCommSq.iso F ψ'.left ψ'.base F').hom
the coherence condition for the left square
- right_coherence : CategoryStruct.comp (CatCommSq.iso G ψ.right ψ.base G').hom (Functor.whiskerRight self.right G') = CategoryStruct.comp (G.whiskerLeft self.base) (CatCommSq.iso G ψ'.right ψ'.base G').hom
the coherence condition for the right square
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the coherence condition for the right square
the coherence condition for the left square
Whiskering left of a CatCospanTransformMorphism by a CatCospanTransform.
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Whiskering right of a CatCospanTransformMorphism by a CatCospanTransform.
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A constructor for isomorphisms of CatCospanTransform's.
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Extract an isomorphism between left components from an isomorphism in
CatCospanTransform F G F' G'.
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Extract an isomorphism between right components from an isomorphism in
CatCospanTransform F G F' G'.
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Extract an isomorphism between base components from an isomorphism in
CatCospanTransform F G F' G'.
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The left unitor isomorphism for categorical cospan transformations.
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The right unitor isomorphism for categorical cospan transformations.
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The associator isomorphism for categorical cospan transformations.
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Whiskering left of a CatCospanTransformMorphism by a CatCospanTransform.
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Whiskering right of a CatCospanTransformMorphism by a CatCospanTransform.
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The associator isomorphism for categorical cospan transformations.
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The left unitor isomorphism for categorical cospan transformations.
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The right unitor isomorphism for categorical cospan transformations.