Pointed maps

Content created by Fredrik Bakke, Egbert Rijke and Jonathan Prieto-Cubides.

Created on 2022-05-07.
Last modified on 2024-03-13.

module structured-types.pointed-maps where
open import foundation.action-on-identifications-dependent-functions
open import foundation.action-on-identifications-functions
open import foundation.constant-maps
open import foundation.dependent-pair-types
open import foundation.function-types
open import foundation.identity-types
open import foundation.transport-along-identifications
open import foundation.universe-levels

open import structured-types.pointed-dependent-functions
open import structured-types.pointed-families-of-types
open import structured-types.pointed-types


A pointed map from a pointed type A to a pointed type B is a base point preserving function from A to B.

The type A →∗ B of pointed maps from A to B is itself pointed by the constant pointed map.


Pointed maps

module _
  {l1 l2 : Level}

  pointed-map : Pointed-Type l1  Pointed-Type l2  UU (l1  l2)
  pointed-map A B = pointed-Π A (constant-Pointed-Fam A B)

  infixr 5 _→∗_
  _→∗_ = pointed-map

Note: the subscript asterisk symbol used for the pointed map type _→∗_, and pointed type constructions in general, is the asterisk operator (agda-input: \ast), not the asterisk *.

module _
  {l1 l2 : Level} {A : Pointed-Type l1} {B : Pointed-Type l2}

  map-pointed-map : A →∗ B  type-Pointed-Type A  type-Pointed-Type B
  map-pointed-map = pr1

  preserves-point-pointed-map :
    (f : A →∗ B) 
    map-pointed-map f (point-Pointed-Type A)  point-Pointed-Type B
  preserves-point-pointed-map = pr2

Precomposing pointed maps

module _
  {l1 l2 l3 : Level} {A : Pointed-Type l1} {B : Pointed-Type l2}
  (C : Pointed-Fam l3 B) (f : A →∗ B)

  precomp-Pointed-Fam : Pointed-Fam l3 A
  pr1 precomp-Pointed-Fam = fam-Pointed-Fam B C  map-pointed-map f
  pr2 precomp-Pointed-Fam =
      ( fam-Pointed-Fam B C)
      ( inv (preserves-point-pointed-map f))
      ( point-Pointed-Fam B C)

  precomp-pointed-Π : pointed-Π B C  pointed-Π A precomp-Pointed-Fam
  pr1 (precomp-pointed-Π g) x =
    function-pointed-Π g (map-pointed-map f x)
  pr2 (precomp-pointed-Π g) =
    ( inv
      ( apd
        ( function-pointed-Π g)
        ( inv (preserves-point-pointed-map f)))) 
    ( ap
      ( tr
        ( fam-Pointed-Fam B C)
        ( inv (preserves-point-pointed-map f)))
      ( preserves-point-function-pointed-Π g))

Composing pointed maps

module _
  {l1 l2 l3 : Level}
  {A : Pointed-Type l1} {B : Pointed-Type l2} {C : Pointed-Type l3}

  map-comp-pointed-map :
    B →∗ C  A →∗ B  type-Pointed-Type A  type-Pointed-Type C
  map-comp-pointed-map g f =
    map-pointed-map g  map-pointed-map f

  preserves-point-comp-pointed-map :
    (g : B →∗ C) (f : A →∗ B) 
    (map-comp-pointed-map g f (point-Pointed-Type A))  point-Pointed-Type C
  preserves-point-comp-pointed-map g f =
    ( ap (map-pointed-map g) (preserves-point-pointed-map f)) 
    ( preserves-point-pointed-map g)

  comp-pointed-map : B →∗ C  A →∗ B  A →∗ C
  pr1 (comp-pointed-map g f) = map-comp-pointed-map g f
  pr2 (comp-pointed-map g f) = preserves-point-comp-pointed-map g f

  infixr 15 _∘∗_

  _∘∗_ : B →∗ C  A →∗ B  A →∗ C
  _∘∗_ = comp-pointed-map

The identity pointed map

module _
  {l1 : Level} {A : Pointed-Type l1}

  id-pointed-map : A →∗ A
  pr1 id-pointed-map = id
  pr2 id-pointed-map = refl

See also

Recent changes