Timings for DDiagram.v

Require Import Basics.

Require Import Diagrams.Graph.

Require Import Diagrams.Diagram.

(** We define here the Graph ∫D, also denoted G·D *)

Definition integral {G : Graph} (D : Diagram G) : Graph.

Proof.

  srapply Build_Graph.

  +

 exact {i : G & D i}.

  +

 intros i j.

    exact {g : G i.1 j.1 & D _f g i.2 = j.2}.

Defined.

(** Then, a dependent diagram E over D is just a diagram over ∫D. *)

Definition DDiagram {G : Graph} (D : Diagram G)
  := Diagram (integral D).

(** Given a dependent diagram, we c.an recover a diagram over G by considering the Σ types. *)

 

Definition diagram_sigma {G : Graph} {D : Diagram G} (E : DDiagram D)
    : Diagram G.

  Proof.

    srapply Build_Diagram.

    -

 intro i.

      exact {x : D i & E (i; x)}.

    -

 intros i j g x.

 simpl in *.

      exists (D _f g x.1).

      exact (@arr _ E (i; x.1) (j; D _f g x.1) (g; idpath) x.2).

  Defined.

  (** A dependent diagram is said equifibered if all its fibers are equivalences. *)

 

Class Equifibered {G : Graph} {D : Diagram G} (E : DDiagram D) := {
    isequifibered i j (g : G i j) (x : D i)
      :: IsEquiv (@arr _ E (i; x) (j; D _f g x) (g; idpath));
  }.