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Mathlib.CategoryTheory.Functor.Currying

Curry and uncurry, as functors. #

We define curry : ((C × D) ⥤ E) ⥤ (C ⥤ (D ⥤ E)) and uncurry : (C ⥤ (D ⥤ E)) ⥤ ((C × D) ⥤ E), and verify that they provide an equivalence of categories currying : (C ⥤ (D ⥤ E)) ≌ ((C × D) ⥤ E).

@[simp]
theorem CategoryTheory.uncurry_obj_map {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor C (CategoryTheory.Functor D E)) {X : C × D} {Y : C × D} (f : X Y) :
(CategoryTheory.uncurry.obj F).map f = CategoryTheory.CategoryStruct.comp ((F.map f.1).app X.2) ((F.obj Y.1).map f.2)
@[simp]
theorem CategoryTheory.uncurry_map_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] :
∀ {X Y : CategoryTheory.Functor C (CategoryTheory.Functor D E)} (T : X Y) (X_1 : C × D), (CategoryTheory.uncurry.map T).app X_1 = (T.app X_1.1).app X_1.2
@[simp]
theorem CategoryTheory.uncurry_obj_obj {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : C × D) :
(CategoryTheory.uncurry.obj F).obj X = (F.obj X.1).obj X.2

The uncurrying functor, taking a functor C ⥤ (D ⥤ E) and producing a functor (C × D) ⥤ E.

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    The object level part of the currying functor. (See curry for the functorial version.)

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      @[simp]
      theorem CategoryTheory.curry_obj_obj_map {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) (X : C) :
      ∀ {X_1 Y : D} (g : X_1 Y), ((CategoryTheory.curry.obj F).obj X).map g = F.map (CategoryTheory.CategoryStruct.id X, g)
      @[simp]
      theorem CategoryTheory.curry_map_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] :
      ∀ {X Y : CategoryTheory.Functor (C × D) E} (T : X Y) (X_1 : C) (Y_1 : D), ((CategoryTheory.curry.map T).app X_1).app Y_1 = T.app (X_1, Y_1)
      @[simp]
      theorem CategoryTheory.curry_obj_map_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) :
      ∀ {X Y : C} (f : X Y) (Y_1 : D), ((CategoryTheory.curry.obj F).map f).app Y_1 = F.map (f, CategoryTheory.CategoryStruct.id Y_1)
      @[simp]
      theorem CategoryTheory.curry_obj_obj_obj {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) (X : C) (Y : D) :
      ((CategoryTheory.curry.obj F).obj X).obj Y = F.obj (X, Y)

      The currying functor, taking a functor (C × D) ⥤ E and producing a functor C ⥤ (D ⥤ E).

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        theorem CategoryTheory.currying_unitIso_inv_app_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : C) (X : D) :
        ((CategoryTheory.currying.unitIso.inv.app X✝¹).app X✝).app X = CategoryTheory.CategoryStruct.id ((X✝¹.obj X✝).obj X)
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        theorem CategoryTheory.currying_counitIso_hom_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor (C × D) E) (X : C × D) :
        (CategoryTheory.currying.counitIso.hom.app X✝).app X = CategoryTheory.CategoryStruct.id (X✝.obj (X.1, X.2))
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        theorem CategoryTheory.currying_inverse_map_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] :
        ∀ {X Y : CategoryTheory.Functor (C × D) E} (T : X Y) (X_1 : C) (Y_1 : D), ((CategoryTheory.currying.inverse.map T).app X_1).app Y_1 = T.app (X_1, Y_1)
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        theorem CategoryTheory.currying_functor_obj_obj {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : C × D) :
        (CategoryTheory.currying.functor.obj F).obj X = (F.obj X.1).obj X.2
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        theorem CategoryTheory.currying_functor_obj_map {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor C (CategoryTheory.Functor D E)) {X : C × D} {Y : C × D} (f : X Y) :
        (CategoryTheory.currying.functor.obj F).map f = CategoryTheory.CategoryStruct.comp ((F.map f.1).app X.2) ((F.obj Y.1).map f.2)
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        theorem CategoryTheory.currying_counitIso_inv_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor (C × D) E) (X : C × D) :
        (CategoryTheory.currying.counitIso.inv.app X✝).app X = CategoryTheory.CategoryStruct.id (X✝.obj (X.1, X.2))
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        theorem CategoryTheory.currying_inverse_obj_obj_obj {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) (X : C) (Y : D) :
        ((CategoryTheory.currying.inverse.obj F).obj X).obj Y = F.obj (X, Y)
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        theorem CategoryTheory.currying_unitIso_hom_app_app_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : C) (X : D) :
        ((CategoryTheory.currying.unitIso.hom.app X✝¹).app X✝).app X = CategoryTheory.CategoryStruct.id ((X✝¹.obj X✝).obj X)
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        theorem CategoryTheory.currying_inverse_obj_obj_map {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) (X : C) :
        ∀ {X_1 Y : D} (g : X_1 Y), ((CategoryTheory.currying.inverse.obj F).obj X).map g = F.map (CategoryTheory.CategoryStruct.id X, g)
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        theorem CategoryTheory.currying_functor_map_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] :
        ∀ {X Y : CategoryTheory.Functor C (CategoryTheory.Functor D E)} (T : X Y) (X_1 : C × D), (CategoryTheory.currying.functor.map T).app X_1 = (T.app X_1.1).app X_1.2
        @[simp]
        theorem CategoryTheory.currying_inverse_obj_map_app {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor (C × D) E) :
        ∀ {X Y : C} (f : X Y) (Y_1 : D), ((CategoryTheory.currying.inverse.obj F).map f).app Y_1 = F.map (f, CategoryTheory.CategoryStruct.id Y_1)

        The equivalence of functor categories given by currying/uncurrying.

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          F.flip is isomorphic to uncurrying F, swapping the variables, and currying.

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            def CategoryTheory.uncurryObjFlip {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] (F : CategoryTheory.Functor C (CategoryTheory.Functor D E)) :
            CategoryTheory.uncurry.obj F.flip (CategoryTheory.Prod.swap D C).comp (CategoryTheory.uncurry.obj F)

            The uncurrying of F.flip is isomorphic to swapping the factors followed by the uncurrying of F.

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              theorem CategoryTheory.whiskeringRight₂_map_app_app_app (B : Type u₁) [CategoryTheory.Category.{v₁, u₁} B] (C : Type u₂) [CategoryTheory.Category.{v₂, u₂} C] (D : Type u₃) [CategoryTheory.Category.{v₃, u₃} D] (E : Type u₄) [CategoryTheory.Category.{v₄, u₄} E] :
              ∀ {X Y : CategoryTheory.Functor C (CategoryTheory.Functor D E)} (f : X Y) (X_1 : CategoryTheory.Functor B C) (Y_1 : CategoryTheory.Functor B D) (c : B), ((((CategoryTheory.whiskeringRight₂ B C D E).map f).app X_1).app Y_1).app c = (f.app (X_1.obj c)).app (Y_1.obj c)
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              theorem CategoryTheory.whiskeringRight₂_obj_map_app_app (B : Type u₁) [CategoryTheory.Category.{v₁, u₁} B] (C : Type u₂) [CategoryTheory.Category.{v₂, u₂} C] (D : Type u₃) [CategoryTheory.Category.{v₃, u₃} D] (E : Type u₄) [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor C (CategoryTheory.Functor D E)) :
              ∀ {X_1 Y : CategoryTheory.Functor B C} (f : X_1 Y) (Y_1 : CategoryTheory.Functor B D) (X_2 : B), ((((CategoryTheory.whiskeringRight₂ B C D E).obj X).map f).app Y_1).app X_2 = (X.map (f.app X_2)).app (Y_1.obj X_2)
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              theorem CategoryTheory.whiskeringRight₂_obj_obj_obj_map (B : Type u₁) [CategoryTheory.Category.{v₁, u₁} B] (C : Type u₂) [CategoryTheory.Category.{v₂, u₂} C] (D : Type u₃) [CategoryTheory.Category.{v₃, u₃} D] (E : Type u₄) [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : CategoryTheory.Functor B C) (Y : CategoryTheory.Functor B D) :
              ∀ {X_1 Y_1 : B} (f : X_1 Y_1), ((((CategoryTheory.whiskeringRight₂ B C D E).obj X✝).obj X).obj Y).map f = CategoryTheory.CategoryStruct.comp ((X✝.map (X.map f)).app (Y.obj X_1)) ((X✝.obj (X.obj Y_1)).map (Y.map f))
              @[simp]
              theorem CategoryTheory.whiskeringRight₂_obj_obj_map_app (B : Type u₁) [CategoryTheory.Category.{v₁, u₁} B] (C : Type u₂) [CategoryTheory.Category.{v₂, u₂} C] (D : Type u₃) [CategoryTheory.Category.{v₃, u₃} D] (E : Type u₄) [CategoryTheory.Category.{v₄, u₄} E] (X : CategoryTheory.Functor C (CategoryTheory.Functor D E)) (X : CategoryTheory.Functor B C) :
              ∀ {X_1 Y : CategoryTheory.Functor B D} (g : X_1 Y) (X_2 : B), ((((CategoryTheory.whiskeringRight₂ B C D E).obj X✝).obj X).map g).app X_2 = (X✝.obj (X.obj X_2)).map (g.app X_2)

              A version of CategoryTheory.whiskeringRight for bifunctors, obtained by uncurrying, applying whiskeringRight and currying back

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                theorem CategoryTheory.Functor.uncurry_obj_curry_obj {B : Type u₁} [CategoryTheory.Category.{v₁, u₁} B] {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] (F : CategoryTheory.Functor (B × C) D) :
                CategoryTheory.uncurry.obj (CategoryTheory.curry.obj F) = F
                theorem CategoryTheory.Functor.curry_obj_injective {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] {F₁ : CategoryTheory.Functor (C × D) E} {F₂ : CategoryTheory.Functor (C × D) E} (h : CategoryTheory.curry.obj F₁ = CategoryTheory.curry.obj F₂) :
                F₁ = F₂
                theorem CategoryTheory.Functor.uncurry_obj_injective {B : Type u₁} [CategoryTheory.Category.{v₁, u₁} B] {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {F₁ : CategoryTheory.Functor B (CategoryTheory.Functor C D)} {F₂ : CategoryTheory.Functor B (CategoryTheory.Functor C D)} (h : CategoryTheory.uncurry.obj F₁ = CategoryTheory.uncurry.obj F₂) :
                F₁ = F₂
                theorem CategoryTheory.Functor.uncurry_obj_curry_obj_flip_flip {B : Type u₁} [CategoryTheory.Category.{v₁, u₁} B] {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] {H : Type u₅} [CategoryTheory.Category.{v₅, u₅} H] (F₁ : CategoryTheory.Functor B C) (F₂ : CategoryTheory.Functor D E) (G : CategoryTheory.Functor (C × E) H) :
                CategoryTheory.uncurry.obj (F₂.comp (F₁.comp (CategoryTheory.curry.obj G)).flip).flip = (F₁.prod F₂).comp G
                theorem CategoryTheory.Functor.uncurry_obj_curry_obj_flip_flip' {B : Type u₁} [CategoryTheory.Category.{v₁, u₁} B] {C : Type u₂} [CategoryTheory.Category.{v₂, u₂} C] {D : Type u₃} [CategoryTheory.Category.{v₃, u₃} D] {E : Type u₄} [CategoryTheory.Category.{v₄, u₄} E] {H : Type u₅} [CategoryTheory.Category.{v₅, u₅} H] (F₁ : CategoryTheory.Functor B C) (F₂ : CategoryTheory.Functor D E) (G : CategoryTheory.Functor (C × E) H) :
                CategoryTheory.uncurry.obj (F₁.comp (F₂.comp (CategoryTheory.curry.obj G).flip).flip) = (F₁.prod F₂).comp G