Local Obligation Tactic := idtac.
Local Open Scope functor_scope.
Program Definition Prod_Functor
{C1 C2 C1' C2' : Category} (F : C1 –≻ C2) (F' : C1' –≻ C2')
: (C1 × C1') –≻ (C2 × C2') :=
{|
FO := fun a => (F _o (fst a), F' _o (snd a))%object;
FA := fun _ _ f => (F _a (fst f), F' _a (snd f))%morphism
|}.
Next Obligation.
intros; cbn; repeat rewrite F_id; trivial.
Qed.
Next Obligation.
intros; cbn; repeat rewrite F_compose; trivial.
Qed.
Definition Bi_Func_1 {Cx C1 C1' Cy : Category} (F : Cx –≻ C1)
(F' : (C1 × C1') –≻ Cy)
: (Cx × C1') –≻ Cy :=
F' ∘ (Prod_Functor F (@Functor_id C1')).
Definition Bi_Func_2 {Cx C1 C1' Cy : Category} (F : Cx –≻ C1')
(F' : (C1 × C1') –≻ Cy) : (C1 × Cx) –≻ Cy :=
Functor_compose (Prod_Functor (@Functor_id C1) F) F'.
Local Hint Extern 2 => cbn.
Local Obligation Tactic := basic_simpl; do 2 auto.
Program Definition Fix_Bi_Func_1 {C1 C1' Cy : Category} (x : C1)
(F : (C1 × C1') –≻ Cy)
: C1' –≻ Cy :=
{|
FO := fun a => (F _o (x, a))%object;
FA := fun _ _ f => (F @_a (_, _) (_, _) (@id _ x, f))%morphism
|}.
Program Definition Fix_Bi_Func_2 {C1 C1' Cy : Category} (x : C1')
(F : (C1 × C1') –≻ Cy)
: C1 –≻ Cy :=
{|
FO := fun a => (F _o (a, x))%object;
FA := fun _ _ f => (F @_a (_, _) (_, _) (f, @id _ x))%morphism
|}.
Program Definition Diag_Func (C : Category) : C –≻ (C × C) :=
{|
FO := fun a => (a, a);
FA := fun _ _ f => (f, f);
F_id := fun _ => eq_refl;
F_compose := fun _ _ _ _ _ => eq_refl
|}.

Theorem Prod_Functor_Cat_Proj {C D D' : Category} (F : C –≻ (D × D')) :
((Prod_Functor ((Cat_Proj1 _ _) ∘ F) ((Cat_Proj2 _ _) ∘ F))
∘ (Diag_Func C))%functor = F.