feat(category): start on proof of yoneda preserves limits and limit functor is left adjoint

hott/algebra/category/constructions/cone.hlean

@@ -3,7 +3,7 @@ Copyright (c) 2015 Floris van Doorn. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Floris van Doorn
 
-Cones
+Cones of a diagram in a category
 -/
 
 import ..nat_trans ..category
@@ -16,38 +16,48 @@ namespace category
   (c : C)
   (η : constant_functor I c ⟹ F)
 
-  local attribute cone_obj.c [coercion]
+  variables {I C D : Precategory} {F : I ⇒ C} {x y z : cone_obj F} {i : I}
+
+  definition cone_to_obj [unfold 4] := @cone_obj.c
+  definition cone_to_nat [unfold 4] (c : cone_obj F) : constant_functor I (cone_to_obj c) ⟹ F :=
+  cone_obj.η c
+
+  local attribute cone_to_obj [coercion]
 
-  variables {I C : Precategory} {F : I ⇒ C} {x y z : cone_obj F}
   structure cone_hom (x y : cone_obj F) :=
   (f : x ⟶ y)
-  (p : Πi, cone_obj.η y i ∘ f = cone_obj.η x i)
+  (p : Πi, cone_to_nat y i ∘ f = cone_to_nat x i)
 
-  local attribute cone_hom.f [coercion]
+  definition cone_to_hom [unfold 6] := @cone_hom.f
+  definition cone_to_eq [unfold 6] (f : cone_hom x y) (i : I)
+    : cone_to_nat y i ∘ (cone_to_hom f) = cone_to_nat x i :=
+  cone_hom.p f i
+
+  local attribute cone_to_hom [coercion]
 
   definition cone_id [constructor] (x : cone_obj F) : cone_hom x x :=
   cone_hom.mk id
               (λi, !id_right)
 
   definition cone_comp [constructor] (g : cone_hom y z) (f : cone_hom x y) : cone_hom x z :=
-  cone_hom.mk (cone_hom.f g ∘ cone_hom.f f)
+  cone_hom.mk (cone_to_hom g ∘ cone_to_hom f)
-              abstract λi, by rewrite [assoc, +cone_hom.p] end
+              abstract λi, by rewrite [assoc, +cone_to_eq] end
 
-  definition cone_obj_eq (p : cone_obj.c x = cone_obj.c y)
+  definition cone_obj_eq (p : cone_to_obj x = cone_to_obj y)
-    (q : Πi, cone_obj.η x i = cone_obj.η y i ∘ hom_of_eq p) : x = y :=
+    (q : Πi, cone_to_nat x i = cone_to_nat y i ∘ hom_of_eq p) : x = y :=
   begin
     induction x, induction y, esimp at *, induction p, apply ap (cone_obj.mk c),
     apply nat_trans_eq, intro i, exact q i ⬝ !id_right
   end
 
-  theorem c_cone_obj_eq (p : cone_obj.c x = cone_obj.c y)
+  theorem c_cone_obj_eq (p : cone_to_obj x = cone_to_obj y)
-    (q : Πi, cone_obj.η x i = cone_obj.η y i ∘ hom_of_eq p) : ap cone_obj.c (cone_obj_eq p q) = p :=
+    (q : Πi, cone_to_nat x i = cone_to_nat y i ∘ hom_of_eq p) : ap cone_to_obj (cone_obj_eq p q) = p :=
   begin
     induction x, induction y, esimp at *, induction p,
     esimp [cone_obj_eq], rewrite [-ap_compose,↑function.compose,ap_constant]
   end
 
-  theorem cone_hom_eq {f f' : cone_hom x y} (q : cone_hom.f f = cone_hom.f f') : f = f' :=
+  theorem cone_hom_eq {f f' : cone_hom x y} (q : cone_to_hom f = cone_to_hom f') : f = f' :=
   begin
     induction f, induction f', esimp at *, induction q, apply ap (cone_hom.mk f),
     apply @is_hprop.elim, apply pi.is_trunc_pi, intro x, apply is_trunc_eq, -- type class fails
@@ -59,7 +69,7 @@ namespace category
   @precategory.mk _ cone_hom
                  abstract begin
                    intro x y,
-                   assert H : cone_hom x y ≃ Σ(f : x ⟶ y), Πi, cone_obj.η y i ∘ f = cone_obj.η x i,
+                   assert H : cone_hom x y ≃ Σ(f : x ⟶ y), Πi, cone_to_nat y i ∘ f = cone_to_nat x i,
                    { fapply equiv.MK,
                      { intro f, induction f, constructor, assumption},
                      { intro v, induction v, constructor, assumption},
@@ -81,16 +91,16 @@ namespace category
   precategory.Mk (precategory_cone F)
 
   variable {F}
-  definition cone_iso_pr1 (h : x ≅ y) : cone_obj.c x ≅ cone_obj.c y :=
+  definition cone_iso_pr1 [constructor] (h : x ≅ y) : cone_to_obj x ≅ cone_to_obj y :=
   iso.MK
-    (cone_hom.f (to_hom h))
+    (cone_to_hom (to_hom h))
-    (cone_hom.f (to_inv h))
+    (cone_to_hom (to_inv h))
-    (ap cone_hom.f (to_left_inverse h))
+    (ap cone_to_hom (to_left_inverse h))
-    (ap cone_hom.f (to_right_inverse h))
+    (ap cone_to_hom (to_right_inverse h))
 
 
-  definition cone_iso.mk (f : cone_obj.c x ≅ cone_obj.c y)
+  definition cone_iso.mk [constructor] (f : cone_to_obj x ≅ cone_to_obj y)
-    (p : Πi, cone_obj.η y i ∘ to_hom f = cone_obj.η x i) : x ≅ y :=
+    (p : Πi, cone_to_nat y i ∘ to_hom f = cone_to_nat x i) : x ≅ y :=
   begin
     fapply iso.MK,
     { exact !cone_hom.mk p},
@@ -102,11 +112,11 @@ namespace category
   end
 
   variables (x y)
-  definition cone_iso_equiv [constructor] : (x ≅ y) ≃ Σ(f : cone_obj.c x ≅ cone_obj.c y),
+  definition cone_iso_equiv [constructor] : (x ≅ y) ≃ Σ(f : cone_to_obj x ≅ cone_to_obj y),
-                                          Πi, cone_obj.η y i ∘ to_hom f = cone_obj.η x i :=
+                                          Πi, cone_to_nat y i ∘ to_hom f = cone_to_nat x i :=
   begin
     fapply equiv.MK,
-    { intro h, exact ⟨cone_iso_pr1 h, cone_hom.p (to_hom h)⟩},
+    { intro h, exact ⟨cone_iso_pr1 h, cone_to_eq (to_hom h)⟩},
     { intro v, exact cone_iso.mk v.1 v.2},
     { intro v, induction v with f p, fapply sigma_eq: esimp,
       { apply iso_eq, reflexivity},
@@ -114,12 +124,11 @@ namespace category
     { intro h, esimp, apply iso_eq, apply cone_hom_eq, reflexivity},
   end
 
-  --set_option pp.implicit true
+  definition cone_eq_equiv : (x = y) ≃ Σ(f : cone_to_obj x = cone_to_obj y),
-  definition cone_eq_equiv : (x = y) ≃ Σ(f : cone_obj.c x = cone_obj.c y),
+                                          Πi, cone_to_nat y i ∘ hom_of_eq f = cone_to_nat x i :=
-                                          Πi, cone_obj.η y i ∘ hom_of_eq f = cone_obj.η x i :=
   begin
     fapply equiv.MK,
-    { intro r, fapply sigma.mk, exact ap cone_obj.c r, induction r, intro i, apply id_right},
+    { intro r, fapply sigma.mk, exact ap cone_to_obj r, induction r, intro i, apply id_right},
     { intro v, induction v with p q, induction x with c η, induction y with c' η', esimp at *,
       apply cone_obj_eq p, esimp, intro i, exact (q i)⁻¹},
     { intro v, induction v with p q, induction x with c η, induction y with c' η', esimp at *,
@@ -137,9 +146,9 @@ namespace category
       intro x y,
       fapply is_equiv_of_equiv_of_homotopy,
       { exact calc
-(x = y) ≃ (Σ(f : cone_obj.c x = cone_obj.c y), Πi, cone_obj.η y i ∘ hom_of_eq f = cone_obj.η x i)
+(x = y) ≃ (Σ(f : cone_to_obj x = cone_to_obj y), Πi, cone_to_nat y i ∘ hom_of_eq f = cone_to_nat x i)
                   : cone_eq_equiv
-    ... ≃ (Σ(f : cone_obj.c x ≅ cone_obj.c y), Πi, cone_obj.η y i ∘ to_hom f = cone_obj.η x i)
+    ... ≃ (Σ(f : cone_to_obj x ≅ cone_to_obj y), Πi, cone_to_nat y i ∘ to_hom f = cone_to_nat x i)
                   : sigma_equiv_sigma !eq_equiv_iso (λa, !equiv.refl)
     ... ≃ (x ≅ y) : cone_iso_equiv },
       { intro p, induction p, esimp [equiv.trans,equiv.symm], esimp [sigma_functor],
@@ -156,5 +165,15 @@ namespace category
 
   end is_univalent
 
+  definition cone_obj_compose [constructor] (G : C ⇒ D) (x : cone_obj F) : cone_obj (G ∘f F) :=
+  begin
+  fapply cone_obj.mk,
+  { exact G x},
+  { fapply change_natural_map,
+    { refine ((G ∘fn cone_to_nat x) ∘n _), apply nat_trans_of_eq, fapply functor_eq: esimp,
+      intro i j k, esimp, rewrite [id_leftright,respect_id]},
+    { intro i, esimp, exact G (cone_to_nat x i)},
+    { intro i, esimp, rewrite [ap010_functor_eq, ▸*, id_right]}}
+  end
 
 end category

hott/algebra/category/functor/equivalence.hlean

@@ -123,7 +123,7 @@ namespace category
       { exact εn},
       { exact adjointify_adjH},
       { exact adjointify_adjK},
-      { exact @(is_iso_nat_trans _) (λc, !is_iso_inverse)},
+      { exact @(is_natural_iso _) (λc, !is_iso_inverse)},
       { unfold εn, apply iso.struct, },
     end
 

hott/algebra/category/limits.hlean

@@ -17,8 +17,7 @@ namespace category
   include C
 
   definition is_terminal [class] (c : ob) := Πd, is_contr (d ⟶ c)
-  definition is_contr_of_is_terminal (c d : ob) [H : is_terminal d]
+  definition is_contr_of_is_terminal (c d : ob) [H : is_terminal d] : is_contr (c ⟶ d) :=
-    : is_contr (c ⟶ d) :=
   H c
 
   local attribute is_contr_of_is_terminal [instance]
@@ -32,7 +31,8 @@ namespace category
   definition eq_terminal_morphism [H : is_terminal c'] (f : c ⟶ c') : f = terminal_morphism c c' :=
   !is_hprop.elim
 
-  definition terminal_iso_terminal {c c' : ob} (H : is_terminal c) (K : is_terminal c') : c ≅ c' :=
+  definition terminal_iso_terminal (c c' : ob) [H : is_terminal c] [K : is_terminal c']
+    : c ≅ c' :=
   iso.MK !terminal_morphism !terminal_morphism !hom_terminal_eq !hom_terminal_eq
 
   local attribute is_terminal [reducible]
@@ -51,15 +51,14 @@ namespace category
   variable {D}
   definition terminal_object_iso_terminal_object (H₁ H₂ : has_terminal_object D)
     : @terminal_object D H₁ ≅ @terminal_object D H₂ :=
-  terminal_iso_terminal (@has_terminal_object.is_terminal D H₁)
+  !terminal_iso_terminal
-                        (@has_terminal_object.is_terminal D H₂)
 
   theorem is_hprop_has_terminal_object [instance] (D : Category)
     : is_hprop (has_terminal_object D) :=
   begin
     apply is_hprop.mk, intro t₁ t₂, induction t₁ with d₁ H₁, induction t₂ with d₂ H₂,
     assert p : d₁ = d₂,
-    { apply eq_of_iso, apply terminal_iso_terminal H₁ H₂},
+    { apply eq_of_iso, apply terminal_iso_terminal},
     induction p, exact ap _ !is_hprop.elim
   end
 
@@ -101,11 +100,73 @@ namespace category
   definition is_terminal_limit_cone [instance] : is_terminal (limit_cone F) :=
   has_terminal_object.is_terminal _
 
+  section specific_limit
+  omit H
+  variable {F}
+  variables (x : cone_obj F) [K : is_terminal x]
+  include K
+
+  definition to_limit_object : D :=
+  cone_to_obj x
+
+  definition to_limit_nat_trans : constant_functor I (to_limit_object x) ⟹ F :=
+  cone_to_nat x
+
+  definition to_limit_morphism (i : I) : to_limit_object x ⟶ F i :=
+  to_limit_nat_trans x i
+
+  theorem to_limit_commute {i j : I} (f : i ⟶ j)
+    : to_fun_hom F f ∘ to_limit_morphism x i = to_limit_morphism x j :=
+  naturality (to_limit_nat_trans x) f ⬝ !id_right
+
+  definition to_limit_cone_obj [constructor] {d : D} {η : Πi, d ⟶ F i}
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) : cone_obj F :=
+  cone_obj.mk d (nat_trans.mk η (λa b f, p f ⬝ !id_right⁻¹))
+
+  definition to_hom_limit {d : D} (η : Πi, d ⟶ F i)
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) : d ⟶ to_limit_object x :=
+  cone_to_hom (terminal_morphism (to_limit_cone_obj x p) x)
+
+  theorem to_hom_limit_commute {d : D} (η : Πi, d ⟶ F i)
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) (i : I)
+    : to_limit_morphism x i ∘ to_hom_limit x η p = η i :=
+  cone_to_eq (terminal_morphism (to_limit_cone_obj x p) x) i
+
+  definition to_limit_cone_hom [constructor] {d : D} {η : Πi, d ⟶ F i}
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) {h : d ⟶ to_limit_object x}
+    (q : Πi, to_limit_morphism x i ∘ h = η i)
+    : cone_hom (to_limit_cone_obj x p) x :=
+  cone_hom.mk h q
+
+  variable {x}
+  theorem to_eq_hom_limit {d : D} {η : Πi, d ⟶ F i}
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) {h : d ⟶ to_limit_object x}
+    (q : Πi, to_limit_morphism x i ∘ h = η i) : h = to_hom_limit x η p :=
+  ap cone_to_hom (eq_terminal_morphism (to_limit_cone_hom x p q))
+
+  theorem to_limit_cone_unique {d : D} {η : Πi, d ⟶ F i}
+    (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j)
+    {h₁ : d ⟶ to_limit_object x} (q₁ : Πi, to_limit_morphism x i ∘ h₁ = η i)
+    {h₂ : d ⟶ to_limit_object x} (q₂ : Πi, to_limit_morphism x i ∘ h₂ = η i): h₁ = h₂ :=
+  to_eq_hom_limit p q₁ ⬝ (to_eq_hom_limit p q₂)⁻¹
+
+  omit K
+  definition to_limit_object_iso_to_limit_object [constructor] (x y : cone_obj F)
+    [K : is_terminal x] [L : is_terminal y] : to_limit_object x ≅ to_limit_object y :=
+  cone_iso_pr1 !terminal_iso_terminal
+
+  end specific_limit
+
+  /-
+    TODO: relate below definitions to above definitions.
+    However, type class resolution seems to fail...
+  -/
+
   definition limit_object : D :=
-  cone_obj.c (limit_cone F)
+  cone_to_obj (limit_cone F)
 
   definition limit_nat_trans : constant_functor I (limit_object F) ⟹ F :=
-  cone_obj.η (limit_cone F)
+  cone_to_nat (limit_cone F)
 
   definition limit_morphism (i : I) : limit_object F ⟶ F i :=
   limit_nat_trans F i
@@ -123,12 +184,12 @@ namespace category
   variable {H}
   definition hom_limit {d : D} (η : Πi, d ⟶ F i)
     (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) : d ⟶ limit_object F :=
-  cone_hom.f (@(terminal_morphism (limit_cone_obj F p) _) (is_terminal_limit_cone _))
+  cone_to_hom (@(terminal_morphism (limit_cone_obj F p) _) (is_terminal_limit_cone _))
 
   theorem hom_limit_commute {d : D} (η : Πi, d ⟶ F i)
     (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) (i : I)
     : limit_morphism F i ∘ hom_limit F η p = η i :=
-  cone_hom.p (@(terminal_morphism (limit_cone_obj F p) _) (is_terminal_limit_cone _)) i
+  cone_to_eq (@(terminal_morphism (limit_cone_obj F p) _) (is_terminal_limit_cone _)) i
 
   definition limit_cone_hom [constructor] {d : D} {η : Πi, d ⟶ F i}
     (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) {h : d ⟶ limit_object F}
@@ -139,7 +200,7 @@ namespace category
   theorem eq_hom_limit {d : D} {η : Πi, d ⟶ F i}
     (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j) {h : d ⟶ limit_object F}
     (q : Πi, limit_morphism F i ∘ h = η i) : h = hom_limit F η p :=
-  ap cone_hom.f (@eq_terminal_morphism _ _ _ _ (is_terminal_limit_cone _) (limit_cone_hom F p q))
+  ap cone_to_hom (@eq_terminal_morphism _ _ _ _ (is_terminal_limit_cone _) (limit_cone_hom F p q))
 
   theorem limit_cone_unique {d : D} {η : Πi, d ⟶ F i}
     (p : Π⦃i j : I⦄ (f : i ⟶ j), to_fun_hom F f ∘ η i = η j)
@@ -153,25 +214,10 @@ namespace category
 
   omit H
 
--- notation `noinstances` t:max := by+ with_options [elaborator.ignore_instances true] (exact t)
--- definition noinstance (t : tactic) : tactic := with_options [elaborator.ignore_instances true] t
-
   variable (F)
   definition limit_object_iso_limit_object [constructor] (H₁ H₂ : has_limits_of_shape D I) :
     @(limit_object F) H₁ ≅ @(limit_object F) H₂ :=
-  begin
+  cone_iso_pr1 !terminal_object_iso_terminal_object
-    fapply iso.MK,
-    { apply hom_limit, apply @(limit_commute F) H₁},
-    { apply @(hom_limit F) H₁, apply limit_commute},
-    { exact abstract begin fapply limit_cone_unique,
-      { apply limit_commute},
-      { intro i, rewrite [assoc, hom_limit_commute], apply hom_limit_commute},
-      { intro i, apply id_right} end end},
-    { exact abstract begin fapply limit_cone_unique,
-      { apply limit_commute},
-      { intro i, rewrite [assoc, hom_limit_commute], apply hom_limit_commute},
-      { intro i, apply id_right} end end}
-  end
 
   definition limit_functor [constructor] (D I : Precategory) [H : has_limits_of_shape D I]
     : D ^c I ⇒ D :=

hott/algebra/category/limits/adjoint.hlean

@@ -0,0 +1,32 @@
+/-
+Copyright (c) 2015 Floris van Doorn. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Floris van Doorn
+
+colimit_functor ⊣ Δ ⊣ limit_functor
+-/
+
+import ..colimits ..functor.adjoint2
+
+open functor category is_trunc prod yoneda --remove
+
+namespace category
+
+  definition limit_functor_adjoint [constructor] (D I : Precategory) [H : has_limits_of_shape D I] :
+    limit_functor D I ⊣ constant_diagram D I :=
+  adjoint.mk'
+  begin
+    fapply natural_iso.MK: esimp,
+    { intro Fd f, induction Fd with F d, esimp at *,
+      exact sorry},
+    { exact sorry},
+    { exact sorry},
+    { exact sorry},
+    { exact sorry}
+  end
+
+  -- set_option pp.universes true
+  -- print Precategory_functor
+  -- print limit_functor_adjoint
+  -- print adjoint.mk'
+end category

hott/algebra/category/limits/functor_preserve.hlean

@@ -0,0 +1,82 @@
+/-
+Copyright (c) 2015 Floris van Doorn. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Floris van Doorn
+
+Functors preserving limits
+-/
+
+import ..colimits ..yoneda
+
+open functor yoneda is_trunc nat_trans
+
+namespace category
+
+  variables {I C D : Precategory} {F : I ⇒ C} {G : C ⇒ D}
+
+  /- notions of preservation of limits -/
+  definition preserves_limits_of_shape [class] (G : C ⇒ D) (I : Precategory)
+    [H : has_limits_of_shape C I] :=
+  Π(F : I ⇒ C), is_terminal (cone_obj_compose G (limit_cone F))
+
+  definition preserves_existing_limits_of_shape [class] (G : C ⇒ D) (I : Precategory) :=
+  Π(F : I ⇒ C) [H : has_terminal_object (cone F)],
+    is_terminal (cone_obj_compose G (terminal_object (cone F)))
+
+  definition preserves_existing_limits [class] (G : C ⇒ D) :=
+  Π(I : Precategory) (F : I ⇒ C) [H : has_terminal_object (cone F)],
+    is_terminal (cone_obj_compose G (terminal_object (cone F)))
+
+  definition preserves_limits [class] (G : C ⇒ D) [H : is_complete C] :=
+  Π(I : Precategory) [H : has_limits_of_shape C I] (F : I ⇒ C),
+    is_terminal (cone_obj_compose G (limit_cone F))
+
+  definition preserves_chosen_limits_of_shape [class] (G : C ⇒ D) (I : Precategory)
+    [H : has_limits_of_shape C I] [H : has_limits_of_shape D I] :=
+  Π(F : I ⇒ C), cone_obj_compose G (limit_cone F) = limit_cone (G ∘f F)
+
+  definition preserves_chosen_limits [class] (G : C ⇒ D)
+    [H : is_complete C] [H : is_complete D] :=
+  Π(I : Precategory) (F : I ⇒ C), cone_obj_compose G (limit_cone F) = limit_cone (G ∘f F)
+
+  /- basic instances -/
+  definition preserves_limits_of_shape_of_preserves_limits [instance] (G : C ⇒ D)
+    (I : Precategory) [H : is_complete C] [H : preserves_limits G]
+    : preserves_limits_of_shape G I := H I
+
+  definition preserves_chosen_limits_of_shape_of_preserves_chosen_limits [instance] (G : C ⇒ D)
+    (I : Precategory) [H : is_complete C] [H : is_complete D] [K : preserves_chosen_limits G]
+    : preserves_chosen_limits_of_shape G I := K I
+
+  /- yoneda preserves existing limits -/
+
+  definition preserves_existing_limits_yoneda_embedding_lemma [constructor] (x : cone_obj F)
+    [H : is_terminal x] {G : Cᵒᵖ ⇒ cset} (η : constant_functor I G ⟹ ɏ ∘f F) :
+    G ⟹ to_fun_ob ɏ (cone_to_obj x) :=
+  begin
+    fapply nat_trans.mk: esimp,
+    { intro c x, fapply to_hom_limit,
+      { intro i, exact η i c x},
+      { intro i j k, exact sorry}},
+    { intro c c' f, apply eq_of_homotopy, intro x, exact sorry}
+  end
+
+  theorem preserves_existing_limits_yoneda_embedding (C : Precategory)
+    : preserves_existing_limits (yoneda_embedding C) :=
+  begin
+    intro I F H Gη, induction H with x H, induction Gη with G η, esimp at *,
+    fapply is_contr.mk,
+    { fapply cone_hom.mk: esimp,
+      { exact sorry
+        -- fapply nat_trans.mk: esimp,
+        -- { intro c x, esimp [yoneda_embedding], fapply to_hom_limit,
+        --   { apply has_terminal_object.is_terminal}, --this should be solved by type class res.
+        --   { intro i, induction dη with d η, esimp at *, },
+        --   {  intro i j k, }},
+        -- { }
+  },
+      { exact sorry}},
+    { exact sorry}
+  end
+
+end category

hott/algebra/category/nat_trans.hlean

@@ -178,7 +178,7 @@ namespace nat_trans
   definition nf_id (η : G ⟹ H) (c : C) : (η ∘nf 1) c = η c :=
   idp
 
-  definition nat_trans_of_eq [reducible] (p : F = G) : F ⟹ G :=
+  definition nat_trans_of_eq [reducible] [constructor] (p : F = G) : F ⟹ G :=
   nat_trans.mk (λc, hom_of_eq (ap010 to_fun_ob p c))
                (λa b f, eq.rec_on p (!id_right ⬝ !id_left⁻¹))
 

hott/algebra/category/yoneda.hlean

@@ -38,10 +38,11 @@ namespace yoneda
   local attribute Category.to.precategory category.to_precategory [constructor]
 
   -- should this be defined as "yoneda_embedding Cᵒᵖ"?
-  definition contravariant_yoneda_embedding [reducible] (C : Precategory) : Cᵒᵖ ⇒ cset ^c C :=
+  definition contravariant_yoneda_embedding [constructor] [reducible]
+    (C : Precategory) : Cᵒᵖ ⇒ cset ^c C :=
   functor_curry !hom_functor
 
-  definition yoneda_embedding (C : Precategory) : C ⇒ cset ^c Cᵒᵖ :=
+  definition yoneda_embedding [constructor] (C : Precategory) : C ⇒ cset ^c Cᵒᵖ :=
   functor_curry (!hom_functor ∘f !prod_flip_functor)
 
   notation `ɏ` := yoneda_embedding _
@@ -66,7 +67,7 @@ namespace yoneda
       exact ap10 !respect_id x end end},
     { exact abstract begin intro η, esimp, apply nat_trans_eq,
       intro c', esimp, apply eq_of_homotopy,
-      intro f, esimp [yoneda_embedding] at f,
+      intro f,
       transitivity (F f ∘ η c) id, reflexivity,
       rewrite naturality, esimp [yoneda_embedding], rewrite [id_left], apply ap _ !id_left end end},
   end
@@ -137,8 +138,8 @@ namespace yoneda
       rewrite -eq_of_iso_refl,
       apply ap eq_of_iso, apply iso_eq, esimp,
       apply nat_trans_eq, intro c',
-      apply eq_of_homotopy, esimp [yoneda_embedding], intro f,
+      apply eq_of_homotopy, intro f,
-      rewrite [category.category.id_left], apply id_right}
+      rewrite [▸*, category.category.id_left], apply id_right}
   end
 
   definition is_representable {C : Precategory} (F : Cᵒᵖ ⇒ cset) := Σ(c : C), ɏ c ≅ F