Timings for Opposite.v

(* -*- mode: coq; mode: visual-line -*-  *)

Require Import Basics.Overture Basics.Tactics.

Require Import WildCat.Core.

(** ** Opposite categories *)

Definition op (A : Type) := A.

Notation "A ^op" := (op A).

(** This stops typeclass search from trying to unfold op. *)

#[global] Typeclasses Opaque op.

Global Instance isgraph_op {A : Type} `{IsGraph A}
  : IsGraph A^op.

Proof.

  apply Build_IsGraph.

  unfold op; exact (fun a b => b $-> a).

Defined.

Global Instance is01cat_op {A : Type} `{Is01Cat A} : Is01Cat A^op.

Proof.

  apply Build_Is01Cat.

  +

 cbv; exact Id.

  +

 cbv; exact (fun a b c g f => f $o g).

Defined.

(** We don't invert 2-cells as this is op on the first level. *)

Global Instance is2graph_op {A : Type} `{Is2Graph A} : Is2Graph A^op.

Proof.

  intros a b; unfold op in *; cbn; exact _.

Defined.

Global Instance is1cat_op {A : Type} `{Is1Cat A} : Is1Cat A^op.

Proof.

  snrapply Build_Is1Cat; unfold op in *; cbv in *.

  -

 intros a b.

    apply is01cat_hom.

  -

 intros a b.

    apply is0gpd_hom.

  -

 intros a b c h.

    srapply Build_Is0Functor.

    intros f g p.

    cbn in *.

    exact (p $@R h).

  -

 intros a b c h.

    srapply Build_Is0Functor.

    intros f g p.

    cbn in *.

    exact (h $@L p).

  -

 intros a b c d f g h; exact (cat_assoc_opp h g f).

  -

 intros a b c d f g h; exact (cat_assoc h g f).

  -

 intros a b f; exact (cat_idr f).

  -

 intros a b f; exact (cat_idl f).

Defined.

Global Instance is1cat_strong_op A `{Is1Cat_Strong A}
  : Is1Cat_Strong (A ^op).

Proof.

  snrapply Build_Is1Cat_Strong.

  1-4: exact _.

  all: cbn.

  -

 intros a b c d f g h; exact (cat_assoc_opp_strong h g f).

  -

 intros a b c d f g h; exact (cat_assoc_strong h g f).

  -

 intros a b f.

    apply cat_idr_strong.

  -

 intros a b f.

    apply cat_idl_strong.

Defined.

(** Opposite groupoids *)

Global Instance is0gpd_op A `{Is0Gpd A} : Is0Gpd (A^op).

Proof.

  srapply Build_Is0Gpd; unfold op in *; cbn in *.

  intros a b.

  apply gpd_rev.

Defined.

Global Instance op0gpd_fun A `{Is0Gpd A} :
  Is0Functor( (fun x => x) : A^op -> A).

Proof.

  srapply Build_Is0Functor; unfold op in *; cbn.

  intros a b.

  exact (fun f => f^$).

Defined.

(** ** Opposite functors *)

Global Instance is0functor_op A B (F : A -> B)
  `{IsGraph A, IsGraph B, x : !Is0Functor F}
  : Is0Functor (F : A^op -> B^op).

Proof.

  apply Build_Is0Functor.

  intros a b; cbn.

  apply fmap.

  assumption.

Defined.

Global Instance is1functor_op A B (F : A -> B)
  `{Is1Cat A, Is1Cat B, !Is0Functor F, !Is1Functor F}
  : Is1Functor (F : A^op -> B^op).

Proof.

  apply Build_Is1Functor; cbn.

  -

 intros a b; rapply fmap2.

  -

 exact (fmap_id F).

  -

 intros a b c f g; exact (fmap_comp F g f).

Defined.

(** Since [Is01Cat] structures are definitionally involutive (see test/WildCat/Opposite.v), we can use [is0functor_op] to transform in the reverse direction as well.  This result makes that much easier to use in practice. *)

Global Instance is0functor_op' A B (F : A^op -> B^op)
  `{IsGraph A, IsGraph B, Fop : !Is0Functor (F : A^op -> B^op)}
  : Is0Functor (F : A -> B)
  := is0functor_op A^op B^op F.

(** [Is1Cat] structures are also definitionally involutive. *)

Global Instance is1functor_op' A B (F : A^op -> B^op)
  `{Is1Cat A, Is1Cat B, !Is0Functor (F : A^op -> B^op), Fop2 : !Is1Functor (F : A^op -> B^op)}
  : Is1Functor (F : A -> B)
  := is1functor_op A^op B^op F.

Global Instance hasmorext_op {A : Type} `{H0 : HasMorExt A}
  : HasMorExt A^op.

Proof.

  snrapply Build_HasMorExt.

  intros a b f g.

  refine (@isequiv_Htpy_path _ _ _ _ _ H0 b a f g).

Defined.

Global Instance isinitial_isterminal_op {A : Type} `{Is1Cat A} (x : A)
  {t : IsTerminal x} : IsInitial (A := A^op) x
  := t.

Global Instance isterminal_isinitial_op {A : Type} `{Is1Cat A} (x : A)
  {i : IsInitial x} : IsTerminal (A := A^op) x
  := i.