Documentation

Mathlib.CategoryTheory.Comma.Basic

Comma categories #

A comma category is a construction in category theory, which builds a category out of two functors with a common codomain. Specifically, for functors L : A ⥤ T and R : B ⥤ T, an object in Comma L R is a morphism hom : L.obj left ⟶ R.obj right for some objects left : A and right : B, and a morphism in Comma L R between hom : L.obj left ⟶ R.obj right and hom' : L.obj left' ⟶ R.obj right' is a commutative square

L.obj left  ⟶  L.obj left'
      |               |
  hom |               | hom'
      ↓               ↓
R.obj right ⟶  R.obj right',

where the top and bottom morphism come from morphisms left ⟶ left' and right ⟶ right', respectively.

Main definitions #

References #

Tags #

comma, slice, coslice, over, under, arrow

The objects of the comma category are triples of an object left : A, an object right : B and a morphism hom : L.obj left ⟶ R.obj right.

  • left : A
  • right : B
  • hom : L.obj self.left R.obj self.right
Instances For
    Equations

    A morphism between two objects in the comma category is a commutative square connecting the morphisms coming from the two objects using morphisms in the image of the functors L and R.

    Instances For
      theorem CategoryTheory.CommaMorphism.ext {A : Type u₁} {inst✝ : CategoryTheory.Category.{v₁, u₁} A} {B : Type u₂} {inst✝¹ : CategoryTheory.Category.{v₂, u₂} B} {T : Type u₃} {inst✝² : CategoryTheory.Category.{v₃, u₃} T} {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L R} {x y : CategoryTheory.CommaMorphism X Y} (left : x.left = y.left) (right : x.right = y.right) :
      x = y
      Equations
      theorem CategoryTheory.Comma.hom_ext {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L R} (f g : X Y) (h₁ : f.left = g.left) (h₂ : f.right = g.right) :
      f = g

      The functor sending an object X in the comma category to X.left.

      Equations
      Instances For

        The functor sending an object X in the comma category to X.right.

        Equations
        Instances For

          We can interpret the commutative square constituting a morphism in the comma category as a natural transformation between the functors fst ⋙ L and snd ⋙ R from the comma category to T, where the components are given by the morphism that constitutes an object of the comma category.

          Equations
          Instances For

            Extract the isomorphism between the left objects from an isomorphism in the comma category.

            Equations
            Instances For

              Extract the isomorphism between the right objects from an isomorphism in the comma category.

              Equations
              Instances For
                def CategoryTheory.Comma.isoMk {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L₁ : CategoryTheory.Functor A T} {R₁ : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L₁ R₁} (l : X.left Y.left) (r : X.right Y.right) (h : CategoryTheory.CategoryStruct.comp (L₁.map l.hom) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R₁.map r.hom) := by aesop_cat) :
                X Y

                Construct an isomorphism in the comma category given isomorphisms of the objects whose forward directions give a commutative square.

                Equations
                • CategoryTheory.Comma.isoMk l r h = { hom := { left := l.hom, right := r.hom, w := h }, inv := { left := l.inv, right := r.inv, w := }, hom_inv_id := , inv_hom_id := }
                Instances For
                  @[simp]
                  theorem CategoryTheory.Comma.isoMk_hom_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L₁ : CategoryTheory.Functor A T} {R₁ : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L₁ R₁} (l : X.left Y.left) (r : X.right Y.right) (h : CategoryTheory.CategoryStruct.comp (L₁.map l.hom) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R₁.map r.hom) := by aesop_cat) :
                  (CategoryTheory.Comma.isoMk l r h).hom.left = l.hom
                  @[simp]
                  theorem CategoryTheory.Comma.isoMk_inv_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L₁ : CategoryTheory.Functor A T} {R₁ : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L₁ R₁} (l : X.left Y.left) (r : X.right Y.right) (h : CategoryTheory.CategoryStruct.comp (L₁.map l.hom) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R₁.map r.hom) := by aesop_cat) :
                  (CategoryTheory.Comma.isoMk l r h).inv.left = l.inv
                  @[simp]
                  theorem CategoryTheory.Comma.isoMk_hom_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L₁ : CategoryTheory.Functor A T} {R₁ : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L₁ R₁} (l : X.left Y.left) (r : X.right Y.right) (h : CategoryTheory.CategoryStruct.comp (L₁.map l.hom) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R₁.map r.hom) := by aesop_cat) :
                  (CategoryTheory.Comma.isoMk l r h).hom.right = r.hom
                  @[simp]
                  theorem CategoryTheory.Comma.isoMk_inv_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {L₁ : CategoryTheory.Functor A T} {R₁ : CategoryTheory.Functor B T} {X Y : CategoryTheory.Comma L₁ R₁} (l : X.left Y.left) (r : X.right Y.right) (h : CategoryTheory.CategoryStruct.comp (L₁.map l.hom) Y.hom = CategoryTheory.CategoryStruct.comp X.hom (R₁.map r.hom) := by aesop_cat) :
                  (CategoryTheory.Comma.isoMk l r h).inv.right = r.inv

                  The functor Comma L R ⥤ Comma L' R' induced by three functors F₁, F₂, F and two natural transformations F₁ ⋙ L' ⟶ L ⋙ F and R ⋙ F ⟶ F₂ ⋙ R'.

                  Equations
                  • One or more equations did not get rendered due to their size.
                  Instances For
                    @[simp]
                    theorem CategoryTheory.Comma.map_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') {X Y : CategoryTheory.Comma L R} (φ : X Y) :
                    ((CategoryTheory.Comma.map α β).map φ).right = F₂.map φ.right
                    @[simp]
                    theorem CategoryTheory.Comma.map_obj_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') (X : CategoryTheory.Comma L R) :
                    ((CategoryTheory.Comma.map α β).obj X).left = F₁.obj X.left
                    @[simp]
                    theorem CategoryTheory.Comma.map_obj_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') (X : CategoryTheory.Comma L R) :
                    ((CategoryTheory.Comma.map α β).obj X).right = F₂.obj X.right
                    @[simp]
                    theorem CategoryTheory.Comma.map_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') {X Y : CategoryTheory.Comma L R} (φ : X Y) :
                    ((CategoryTheory.Comma.map α β).map φ).left = F₁.map φ.left
                    instance CategoryTheory.Comma.faithful_map {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') [F₁.Faithful] [F₂.Faithful] :
                    (CategoryTheory.Comma.map α β).Faithful
                    Equations
                    • =
                    instance CategoryTheory.Comma.full_map {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') [F.Faithful] [F₁.Full] [F₂.Full] [CategoryTheory.IsIso α] [CategoryTheory.IsIso β] :
                    Equations
                    • =
                    instance CategoryTheory.Comma.essSurj_map {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') [F₁.EssSurj] [F₂.EssSurj] [F.Full] [CategoryTheory.IsIso α] [CategoryTheory.IsIso β] :
                    (CategoryTheory.Comma.map α β).EssSurj
                    Equations
                    • =
                    noncomputable instance CategoryTheory.Comma.isEquivalenceMap {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] {A' : Type u₄} [CategoryTheory.Category.{v₄, u₄} A'] {B' : Type u₅} [CategoryTheory.Category.{v₅, u₅} B'] {T' : Type u₆} [CategoryTheory.Category.{v₆, u₆} T'] {L : CategoryTheory.Functor A T} {R : CategoryTheory.Functor B T} {L' : CategoryTheory.Functor A' T'} {R' : CategoryTheory.Functor B' T'} {F₁ : CategoryTheory.Functor A A'} {F₂ : CategoryTheory.Functor B B'} {F : CategoryTheory.Functor T T'} (α : F₁.comp L' L.comp F) (β : R.comp F F₂.comp R') [F₁.IsEquivalence] [F₂.IsEquivalence] [F.Faithful] [F.Full] [CategoryTheory.IsIso α] [CategoryTheory.IsIso β] :
                    (CategoryTheory.Comma.map α β).IsEquivalence
                    Equations
                    • =
                    @[simp]

                    The equality between map α β ⋙ fst L' R' and fst L R ⋙ F₁, where α : F₁ ⋙ L' ⟶ L ⋙ F.

                    The isomorphism between map α β ⋙ fst L' R' and fst L R ⋙ F₁, where α : F₁ ⋙ L' ⟶ L ⋙ F.

                    Equations
                    • One or more equations did not get rendered due to their size.
                    Instances For
                      @[simp]

                      The equality between map α β ⋙ snd L' R' and snd L R ⋙ F₂, where β : R ⋙ F ⟶ F₂ ⋙ R'.

                      The isomorphism between map α β ⋙ snd L' R' and snd L R ⋙ F₂, where β : R ⋙ F ⟶ F₂ ⋙ R'.

                      Equations
                      • One or more equations did not get rendered due to their size.
                      Instances For

                        A natural transformation L₁ ⟶ L₂ induces a functor Comma L₂ R ⥤ Comma L₁ R.

                        Equations
                        • One or more equations did not get rendered due to their size.
                        Instances For
                          @[simp]
                          theorem CategoryTheory.Comma.mapLeft_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (l : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₂ R} (f : X✝ Y✝) :
                          ((CategoryTheory.Comma.mapLeft R l).map f).right = f.right
                          @[simp]
                          theorem CategoryTheory.Comma.mapLeft_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (l : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₂ R} (f : X✝ Y✝) :
                          ((CategoryTheory.Comma.mapLeft R l).map f).left = f.left

                          The functor Comma L R ⥤ Comma L R induced by the identity natural transformation on L is naturally isomorphic to the identity functor.

                          Equations
                          • One or more equations did not get rendered due to their size.
                          Instances For

                            The functor Comma L₁ R ⥤ Comma L₃ R induced by the composition of two natural transformations l : L₁ ⟶ L₂ and l' : L₂ ⟶ L₃ is naturally isomorphic to the composition of the two functors induced by these natural transformations.

                            Equations
                            • One or more equations did not get rendered due to their size.
                            Instances For

                              Two equal natural transformations L₁ ⟶ L₂ yield naturally isomorphic functors Comma L₁ R ⥤ Comma L₂ R.

                              Equations
                              • One or more equations did not get rendered due to their size.
                              Instances For

                                A natural isomorphism L₁ ≅ L₂ induces an equivalence of categories Comma L₁ R ≌ Comma L₂ R.

                                Equations
                                • One or more equations did not get rendered due to their size.
                                Instances For
                                  @[simp]
                                  theorem CategoryTheory.Comma.mapLeftIso_inverse_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (i : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₂ R} (f : X✝ Y✝) :
                                  ((CategoryTheory.Comma.mapLeftIso R i).inverse.map f).right = f.right
                                  @[simp]
                                  theorem CategoryTheory.Comma.mapLeftIso_functor_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (i : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₁ R} (f : X✝ Y✝) :
                                  ((CategoryTheory.Comma.mapLeftIso R i).functor.map f).right = f.right
                                  @[simp]
                                  theorem CategoryTheory.Comma.mapLeftIso_inverse_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (i : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₂ R} (f : X✝ Y✝) :
                                  ((CategoryTheory.Comma.mapLeftIso R i).inverse.map f).left = f.left
                                  @[simp]
                                  theorem CategoryTheory.Comma.mapLeftIso_functor_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (R : CategoryTheory.Functor B T) {L₁ L₂ : CategoryTheory.Functor A T} (i : L₁ L₂) {X✝ Y✝ : CategoryTheory.Comma L₁ R} (f : X✝ Y✝) :
                                  ((CategoryTheory.Comma.mapLeftIso R i).functor.map f).left = f.left

                                  A natural transformation R₁ ⟶ R₂ induces a functor Comma L R₁ ⥤ Comma L R₂.

                                  Equations
                                  • One or more equations did not get rendered due to their size.
                                  Instances For
                                    @[simp]
                                    theorem CategoryTheory.Comma.mapRight_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (r : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₁} (f : X✝ Y✝) :
                                    ((CategoryTheory.Comma.mapRight L r).map f).right = f.right
                                    @[simp]
                                    theorem CategoryTheory.Comma.mapRight_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (r : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₁} (f : X✝ Y✝) :
                                    ((CategoryTheory.Comma.mapRight L r).map f).left = f.left

                                    The functor Comma L R ⥤ Comma L R induced by the identity natural transformation on R is naturally isomorphic to the identity functor.

                                    Equations
                                    • One or more equations did not get rendered due to their size.
                                    Instances For

                                      The functor Comma L R₁ ⥤ Comma L R₃ induced by the composition of the natural transformations r : R₁ ⟶ R₂ and r' : R₂ ⟶ R₃ is naturally isomorphic to the composition of the functors induced by these natural transformations.

                                      Equations
                                      • One or more equations did not get rendered due to their size.
                                      Instances For

                                        Two equal natural transformations R₁ ⟶ R₂ yield naturally isomorphic functors Comma L R₁ ⥤ Comma L R₂.

                                        Equations
                                        • One or more equations did not get rendered due to their size.
                                        Instances For

                                          A natural isomorphism R₁ ≅ R₂ induces an equivalence of categories Comma L R₁ ≌ Comma L R₂.

                                          Equations
                                          • One or more equations did not get rendered due to their size.
                                          Instances For
                                            @[simp]
                                            theorem CategoryTheory.Comma.mapRightIso_functor_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (i : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₁} (f : X✝ Y✝) :
                                            ((CategoryTheory.Comma.mapRightIso L i).functor.map f).left = f.left
                                            @[simp]
                                            theorem CategoryTheory.Comma.mapRightIso_inverse_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (i : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₂} (f : X✝ Y✝) :
                                            ((CategoryTheory.Comma.mapRightIso L i).inverse.map f).right = f.right
                                            @[simp]
                                            theorem CategoryTheory.Comma.mapRightIso_inverse_map_left {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (i : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₂} (f : X✝ Y✝) :
                                            ((CategoryTheory.Comma.mapRightIso L i).inverse.map f).left = f.left
                                            @[simp]
                                            theorem CategoryTheory.Comma.mapRightIso_functor_map_right {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) {R₁ R₂ : CategoryTheory.Functor B T} (i : R₁ R₂) {X✝ Y✝ : CategoryTheory.Comma L R₁} (f : X✝ Y✝) :
                                            ((CategoryTheory.Comma.mapRightIso L i).functor.map f).right = f.right

                                            The functor (F ⋙ L, R) ⥤ (L, R)

                                            Equations
                                            • One or more equations did not get rendered due to their size.
                                            Instances For

                                              Comma.preLeft is a particular case of Comma.map, but with better definitional properties.

                                              Equations
                                              • One or more equations did not get rendered due to their size.
                                              Instances For

                                                If F is an equivalence, then so is preLeft F L R.

                                                Equations
                                                • =

                                                The functor (F ⋙ L, R) ⥤ (L, R)

                                                Equations
                                                • One or more equations did not get rendered due to their size.
                                                Instances For

                                                  Comma.preRight is a particular case of Comma.map, but with better definitional properties.

                                                  Equations
                                                  • One or more equations did not get rendered due to their size.
                                                  Instances For

                                                    If F is an equivalence, then so is preRight L F R.

                                                    Equations
                                                    • =

                                                    The functor (L, R) ⥤ (L ⋙ F, R ⋙ F)

                                                    Equations
                                                    • One or more equations did not get rendered due to their size.
                                                    Instances For

                                                      Comma.post is a particular case of Comma.map, but with better definitional properties.

                                                      Equations
                                                      • One or more equations did not get rendered due to their size.
                                                      Instances For

                                                        If F is an equivalence, then so is post L R F.

                                                        Equations
                                                        • =

                                                        The canonical functor from the product of two categories to the comma category of their respective functors into Discrete PUnit.

                                                        Equations
                                                        • One or more equations did not get rendered due to their size.
                                                        Instances For

                                                          Taking the comma category of two functors into Discrete PUnit results in something is equivalent to their product.

                                                          Equations
                                                          • One or more equations did not get rendered due to their size.
                                                          Instances For

                                                            The canonical functor from Comma L R to (Comma R.op L.op)ᵒᵖ.

                                                            Equations
                                                            • One or more equations did not get rendered due to their size.
                                                            Instances For

                                                              The canonical functor from Comma L.op R.op to (Comma R L)ᵒᵖ.

                                                              Equations
                                                              • One or more equations did not get rendered due to their size.
                                                              Instances For
                                                                @[simp]
                                                                theorem CategoryTheory.Comma.unopFunctor_map {A : Type u₁} [CategoryTheory.Category.{v₁, u₁} A] {B : Type u₂} [CategoryTheory.Category.{v₂, u₂} B] {T : Type u₃} [CategoryTheory.Category.{v₃, u₃} T] (L : CategoryTheory.Functor A T) (R : CategoryTheory.Functor B T) {X✝ Y✝ : CategoryTheory.Comma L.op R.op} (f : X✝ Y✝) :
                                                                (CategoryTheory.Comma.unopFunctor L R).map f = Opposite.op { left := f.right.unop, right := f.left.unop, w := }

                                                                The canonical equivalence between Comma L R and (Comma R.op L.op)ᵒᵖ.

                                                                Equations
                                                                • One or more equations did not get rendered due to their size.
                                                                Instances For