Timings for Pointwise.v

Require Import Basics Types Pointed HSpace.Core HSpace.Coherent.

Local Open Scope pointed_scope.

Local Open Scope mc_mult_scope.

(** * Pointwise H-space structures *)

(** Whenever [X] is an H-space, so is the type of maps into [X]. *)

Global Instance ishspace_map `{Funext} (X : pType) (Y : Type)
  `{IsHSpace X} : IsHSpace [Y -> X, const pt].

(* Note: When writing [f * g], Coq only finds this instance if [f] is explicitly in the pointed type [[Y -> X, const pt]]. *)

Proof.

  snrapply Build_IsHSpace.

  -

 exact (fun f g y => (f y) * (g y)).

  -

 intro g; funext y.

    apply hspace_left_identity.

  -

 intro f; funext y.

    apply hspace_right_identity.

Defined.

(** If [X] is coherent, so is [[Y -> X, const pt]]. *)

Global Instance iscoherent_ishspace_map `{Funext} (X : pType) (Y : Type)
  `{IsCoherent X} : IsCoherent [Y -> X, const pt].

Proof.

  hnf; cbn.

  refine (ap _ _).

  funext y; apply iscoherent.

Defined.

(** If [X] is left-invertible, so is [[Y -> X, const pt]]. *)

Global Instance isleftinvertible_hspace_map `{Funext} (X : pType) (Y : Type)
  `{IsHSpace X} `{forall x, IsEquiv (x *.)}
  : forall f : [Y -> X, const pt], IsEquiv (f *.).

Proof.

  intro f; cbn.

  (** Left multiplication by [f] unifies with [functor_forall]. *)
 

exact (isequiv_functor_forall (P:=const X) (f:=idmap)
           (g:=fun y gy => (f y) * gy)).

Defined.

(** For the type of pointed maps [Y ->** X], coherence of [X] is needed even to get a noncoherent H-space structure on [Y ->** X]. *)

Global Instance ishspace_pmap `{Funext} (X Y : pType) `{IsCoherent X}
  : IsHSpace (Y ->** X).

Proof.

  snrapply Build_IsHSpace.

  -

 intros f g.

    snrapply Build_pMap.

    +

 exact (fun y => hspace_op (f y) (g y)).

    +

 cbn.

      refine (ap _ (point_eq g) @ _); cbn.

      refine (ap (.* pt) (point_eq f) @ _).

      apply hspace_left_identity.

  -

 intro g.

    apply path_pforall.

    snrapply Build_pHomotopy.

    +

 intro y; cbn.

      apply hspace_left_identity.

    +

 cbn.

      apply moveL_pV.

      exact (1 @@ concat_1p _ @ concat_A1p _ _)^.

  -

 intro f.

    apply path_pforall.

    snrapply Build_pHomotopy.

    +

 intro y; cbn.

      apply hspace_right_identity.

    +

 pelim f; cbn.

      symmetry.

      lhs nrapply (concat_p1 _ @ concat_1p _ @ concat_1p _).

      apply iscoherent.

Defined.

Global Instance iscoherent_hspace_pmap `{Funext} (X Y : pType) `{IsCoherent X}
  : IsCoherent (Y ->** X).

Proof.

  (* Note that [pt] sometimes means the constant map [Y ->* X]. *)
 

unfold IsCoherent.

  (* Both identities are created using [path_pforall]. *)
 

refine (ap path_pforall _).

  apply path_pforall.

  snrapply Build_pHomotopy.

  -

 intro y; cbn.

    apply iscoherent.

  -

 cbn.

    generalize iscoherent as isc.

    unfold left_identity, right_identity.

    (* The next line is essentially the same as [generalize], but for some reason that tactic doesn't work here. *)
   

set (p := hspace_left_identity pt); clearbody p.

    intros [].

    induction p.

    reflexivity.

Defined.

(** If the H-space structure on [X] is left-invertible, so is the one induced on [Y ->** X]. *)

Global Instance isleftinvertible_hspace_pmap `{Funext} (X Y : pType)
  `{IsCoherent X} `{forall x, IsEquiv (x *.)}
  : forall f : Y ->** X, IsEquiv (f *.).

Proof.

  intro f.

  srefine (isequiv_homotopic (equiv_functor_pforall_id _ _) _).

  -

 exact (fun a => equiv_hspace_left_op (f a)).

  -

 cbn.

 exact (right_identity _ @ point_eq f).

  -

 intro g.

    apply path_pforall; snrapply Build_pHomotopy.

    +

 intro y; cbn.

      reflexivity.

    +

 cbn.

 apply (moveR_1M _ _)^-1.

      apply whiskerL.

      refine (whiskerL _ iscoherent @ _).

      exact (concat_A1p right_identity (point_eq f)).

Defined.