39 lines
1.3 KiB
Text
39 lines
1.3 KiB
Text
-- Copyright (c) 2014 Jakob von Raumer. All rights reserved.
|
||
-- Released under Apache 2.0 license as described in the file LICENSE.
|
||
-- Author: Jakob von Raumer
|
||
-- Ported from Coq HoTT
|
||
import hott.path hott.trunc data.sigma data.prod
|
||
|
||
open path prod truncation
|
||
|
||
inductive is_pointed [class] (A : Type) :=
|
||
pointed_mk : Π(a : A), is_pointed A
|
||
|
||
namespace is_pointed
|
||
variables {A B : Type.{1}} (f : A → B)
|
||
|
||
definition point (A : Type) [H : is_pointed A] : A :=
|
||
is_pointed.rec (λinv, inv) H
|
||
|
||
-- Any contractible type is pointed
|
||
protected definition contr [instance] [H : is_contr A] : is_pointed A :=
|
||
pointed_mk (center A)
|
||
|
||
-- A pi type with a pointed target is pointed
|
||
protected definition pi [instance] {P : A → Type} [H : Πx, is_pointed (P x)]
|
||
: is_pointed (Πx, P x) :=
|
||
pointed_mk (λx, point (P x))
|
||
|
||
-- A sigma type of pointed components is pointed
|
||
protected definition sigma [instance] {P : A → Type} [G : is_pointed A]
|
||
[H : is_pointed (P (point A))] : is_pointed (Σx, P x) :=
|
||
pointed_mk (sigma.dpair (point A) (point (P (point A))))
|
||
|
||
protected definition prod [H1 : is_pointed A] [H2 : is_pointed B]
|
||
: is_pointed (A × B) :=
|
||
pointed_mk (prod.mk (point A) (point B))
|
||
|
||
protected definition loop_space (a : A) : is_pointed (a ≈ a) :=
|
||
pointed_mk idp
|
||
|
||
end is_pointed
|