Library UniMath.CategoryTheory.Hyperdoctrines.PartialEqRels.Logic.Conjunction

1. The formula

    Proposition per_subobject_conj_laws
      : per_subobject_laws (ψ ψ).
    Proof.
      split.
      - use forall_intro.
        use impl_intro.
        use weaken_right.
        hypersimplify.
        use weaken_right.
        use (per_subobject_def ψ).
        apply hyperdoctrine_hyp.
      - do 2 use forall_intro.
        use impl_intro.
        use weaken_right.
        use impl_intro.
        hypersimplify.
        pose (γ₁ := π (tm_var ((𝟙 ×h Γ) ×h Γ)))).
        pose (γ₂ := π (tm_var ((𝟙 ×h Γ) ×h Γ))).
        fold γ₁ γ₂.
        use conj_intro.
        + use (per_subobject_eq ψ).
          * exact γ₁.
          * use weaken_left.
            apply hyperdoctrine_hyp.
          * use weaken_right.
            use weaken_left.
            apply hyperdoctrine_hyp.
        + use (per_subobject_eq ψ).
          * exact γ₁.
          * use weaken_left.
            apply hyperdoctrine_hyp.
          * do 2 use weaken_right.
            apply hyperdoctrine_hyp.
    Qed.

    Definition per_subobject_conj
      : per_subobject Γ.
    Proof.
      use make_per_subobject.
      - exact (ψ ψ).
      - exact per_subobject_conj_laws.
    Defined.

2. Elimination rules

    Proposition per_subobject_conj_elim_left
      : per_subobject_mor_law
          (id_partial_setoid_morphism Γ)
          per_subobject_conj
          ψ.
    Proof.
      do 2 use forall_intro.
      use impl_intro.
      use weaken_right.
      use impl_intro.
      cbn.
      hypersimplify.
      pose (γ₁ := π (tm_var ((𝟙 ×h Γ) ×h Γ)))).
      pose (γ₂ := π (tm_var ((𝟙 ×h Γ) ×h Γ))).
      fold γ₁ γ₂.
      use per_subobject_eq.
      - exact γ₁.
      - use weaken_left.
        apply hyperdoctrine_hyp.
      - use weaken_right.
        use weaken_left.
        apply hyperdoctrine_hyp.
    Qed.

    Proposition per_subobject_conj_elim_right
      : per_subobject_mor_law
          (id_partial_setoid_morphism Γ)
          per_subobject_conj
          ψ.
    Proof.
      do 2 use forall_intro.
      use impl_intro.
      use weaken_right.
      use impl_intro.
      cbn.
      hypersimplify.
      pose (γ₁ := π (tm_var ((𝟙 ×h Γ) ×h Γ)))).
      pose (γ₂ := π (tm_var ((𝟙 ×h Γ) ×h Γ))).
      fold γ₁ γ₂.
      use per_subobject_eq.
      - exact γ₁.
      - use weaken_left.
        apply hyperdoctrine_hyp.
      - do 2 use weaken_right.
        apply hyperdoctrine_hyp.
    Qed.

3. Introduction rule

    Context {χ : per_subobject Γ}
            (p : per_subobject_mor_law (id_partial_setoid_morphism Γ) χ ψ)
            (q : per_subobject_mor_law (id_partial_setoid_morphism Γ) χ ψ).

    Proposition per_subobject_conj_intro
      : per_subobject_mor_law
          (id_partial_setoid_morphism Γ)
          χ
          per_subobject_conj.
    Proof.
      do 2 use forall_intro.
      use impl_intro.
      use weaken_right.
      use impl_intro.
      cbn.
      hypersimplify.
      pose (γ₁ := π (tm_var ((𝟙 ×h Γ) ×h Γ)))).
      pose (γ₂ := π (tm_var ((𝟙 ×h Γ) ×h Γ))).
      fold γ₁ γ₂.
      use conj_intro.
      - use (per_subobject_mor p).
        + exact γ₁.
        + cbn.
          hypersimplify.
          use weaken_left.
          apply hyperdoctrine_hyp.
        + use weaken_right.
          apply hyperdoctrine_hyp.
      - use (per_subobject_mor q).
        + exact γ₁.
        + cbn.
          hypersimplify.
          use weaken_left.
          apply hyperdoctrine_hyp.
        + use weaken_right.
          apply hyperdoctrine_hyp.
    Qed.
  End Conjunction.

4. Stability under substitution

  Proposition per_subobject_conj_subst
              {Γ₁ Γ₂ : partial_setoid H}
              (s : partial_setoid_morphism Γ₁ Γ₂)
              (ψ ψ : per_subobject Γ₂)
    : per_subobject_mor_law
        (id_partial_setoid_morphism Γ₁)
        (per_subobject_conj
           (per_subobject_subst s ψ)
           (per_subobject_subst s ψ))
        (per_subobject_subst
           s
           (per_subobject_conj ψ ψ)).
  Proof.
    do 2 use forall_intro.
    use impl_intro.
    use weaken_right.
    use impl_intro.
    cbn.
    rewrite partial_setoid_subst.
    rewrite conj_subst.
    rewrite !exists_subst.
    use hyp_sym.
    use hyp_ltrans.
    use (exists_elim (weaken_left (hyperdoctrine_hyp _) _)).
    rewrite !conj_subst.
    use hyp_ltrans.
    use weaken_right.
    use hyp_ltrans.
    rewrite exists_subst.
    use (exists_elim (weaken_left (hyperdoctrine_hyp _) _)).
    rewrite !conj_subst.
    use hyp_ltrans.
    use weaken_right.
    hypersimplify_form.
    hypersimplify.
    pose (γ₁ := π (tm_var ((((𝟙 ×h Γ₁) ×h Γ₁) ×h Γ₂) ×h Γ₂)))))).
    pose (γ₁' := π (tm_var ((((𝟙 ×h Γ₁) ×h Γ₁) ×h Γ₂) ×h Γ₂))))).
    pose (γ₂ := π (tm_var ((((𝟙 ×h Γ₁) ×h Γ₁) ×h Γ₂) ×h Γ₂)))).
    pose (γ₂' := π (tm_var ((((𝟙 ×h Γ₁) ×h Γ₁) ×h Γ₂) ×h Γ₂))).
    use exists_intro.
    {
      exact γ₂.
    }
    hypersimplify.
    fold γ₁ γ₁' γ₂ γ₂'.
    assert ((γ₁ ~ γ₁' s [ γ₁, γ₂ ] ψ [γ₂]) s [ γ₁, γ₂' ] ψ [γ₂'] γ₂ ~ γ₂')
      as r.
    {
      use (partial_setoid_mor_unique_im s).
      - exact γ₁.
      - use weaken_left.
        use weaken_right.
        use weaken_left.
        apply hyperdoctrine_hyp.
      - use weaken_right.
        use weaken_left.
        apply hyperdoctrine_hyp.
    }
    repeat (use conj_intro).
    - use weaken_left.
      use (partial_setoid_mor_eq_defined s).
      + exact γ₁.
      + exact γ₂.
      + use weaken_left.
        apply hyperdoctrine_hyp.
      + use weaken_right.
        use weaken_left.
        exact (partial_setoid_mor_cod_defined s _ _ (hyperdoctrine_hyp _)).
      + use weaken_right.
        use weaken_left.
        apply hyperdoctrine_hyp.
    - use weaken_left.
      do 2 use weaken_right.
      apply hyperdoctrine_hyp.
    - use per_subobject_eq.
      + exact γ₂'.
      + use partial_setoid_sym.
        exact r.
      + do 2 use weaken_right.
        apply hyperdoctrine_hyp.
  Qed.

5. Fiberwise binary products

  Definition fiberwise_binproducts_per_subobject
    : fiberwise_binproducts (disp_cat_per_subobject_cleaving H).
  Proof.
    use make_fiberwise_binproducts_locally_propositional.
    - apply locally_prop_disp_cat_per_subobject.
    - intros Γ ψ ψ.
      exact (per_subobject_conj ψ ψ).
    - intros Γ ψ ψ.
      exact (per_subobject_conj_elim_left ψ ψ).
    - intros Γ ψ ψ.
      exact (per_subobject_conj_elim_right ψ ψ).
    - intros Γ ψ ψ χ p q.
      exact (per_subobject_conj_intro ψ ψ p q).
    - intros Γ₁ Γ₂ s ψ ψ.
      exact (per_subobject_conj_subst s ψ ψ).
  Defined.
End Conjunction.