Lemma bifunctor_on_morphisms_comm {A B C : category} (F : A ⊠ B ⟶ C) {a a' : A} {b b' : B} (f : a --> a') (g : b --> b') : #F (f #, identity _) · #F (identity _ #, g) = #F (identity _ #, g) · #F (f #, identity _). Proof. rewrite <- !functor_comp. change ((?x #, ?y) · (?z #, ?w)) with (x · z #, y · w). rewrite !id_left, !id_right. reflexivity. Qed.
Require Import UniMath.Foundations.PartA. Require Import UniMath.Foundations.Propositions. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.Core.NaturalTransformations. Require Import UniMath.CategoryTheory.Monoidal.Categories. Require Import UniMath.CategoryTheory.PrecategoryBinProduct. Require Import UniMath.CategoryTheory.Core.Isos. Import MonoidalNotations.