proposition: Proposition double_hor_comp_transport_mor {C : category} {D : twosided_disp_cat C C} {Cm : hor_comp D} {x₁ x₂ x₃ y₁ y₂ y₃ z₁ z₂ z₃ : C} {v₁ : x₁ --> x₂} {v₁' : x₂ --> x₃} {v₂ : y₁ --> y₂} {v₂' : y₂ --> y₃} {v₂'' : y₂ --> y₃} {v₃ : z₁ --> z₂} {v₃' : z₂ --> z₃} {u₁ : x₁ --> x₃} {u₂ : y₁ --> y₃} {u₃ : z₁ --> z₃} {h₁ : D x₁ y₁} {h₂ : D y₁ z₁} {k₁ : D x₂ y₂} {k₂ : D y₂ z₂} {l₁ : D x₃ y₃} {l₂ : D y₃ z₃} (s₁ : h₁ -->[ v₁ ][ v₂ ] k₁) (s₁' : k₁ -->[ v₁' ][ v₂'] l₁) (s₂ : h₂ -->[ v₂ ][ v₃ ] k₂) (s₂' : k₂ -->[ v₂'' ][ v₃' ] l₂) (p : v₁ · v₁' = u₁) (q : v₂ · v₂' = u₂) (q' : v₂ · v₂'' = u₂) (s : v₂' = v₂'') (r : v₃ · v₃' = u₃) : double_hor_comp_mor Cm (transportf_disp_mor2 p q (s₁ ;;2 s₁')) (transportf_disp_mor2 q' r (s₂ ;;2 s₂')) = transportf_disp_mor2 p r (double_hor_comp_mor Cm s₁ s₂ ;;2 double_hor_comp_mor Cm (transportf_disp_mor2 (idpath _) s s₁') s₂').
proof: Proof. induction p, q, s, r. assert (q' = idpath _) as H. { apply homset_property. } rewrite H. cbn. rewrite double_hor_comp_mor_comp. apply idpath. Qed.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.TwoSidedDispCat UniMath.CategoryTheory.TwoSidedDisplayedCats.Isos