lean2/hott/init/pathover.hlean
2015-09-30 17:41:44 -07:00

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/-
Copyright (c) 2015 Floris van Doorn. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Floris van Doorn
Basic theorems about pathovers
-/
prelude
import .path .equiv
open equiv is_equiv equiv.ops function
variables {A A' : Type} {B B' : A → Type} {B'' : A' → Type} {C : Π⦃a⦄, B a → Type}
{a a₂ a₃ a₄ : A} {p p' : a = a₂} {p₂ : a₂ = a₃} {p₃ : a₃ = a₄}
{b b' : B a} {b₂ b₂' : B a₂} {b₃ : B a₃} {b₄ : B a₄}
{c : C b} {c₂ : C b₂}
namespace eq
inductive pathover.{l} (B : A → Type.{l}) (b : B a) : Π{a₂ : A}, a = a₂ → B a₂ → Type.{l} :=
idpatho : pathover B b (refl a) b
notation b ` =[`:50 p:0 `] `:0 b₂:50 := pathover _ b p b₂
definition idpo [reducible] [constructor] : b =[refl a] b :=
pathover.idpatho b
/- equivalences with equality using transport -/
definition pathover_of_tr_eq [unfold 5 8] (r : p ▸ b = b₂) : b =[p] b₂ :=
by cases p; cases r; constructor
definition pathover_of_eq_tr [unfold 5 8] (r : b = p⁻¹ ▸ b₂) : b =[p] b₂ :=
by cases p; cases r; constructor
definition tr_eq_of_pathover [unfold 8] (r : b =[p] b₂) : p ▸ b = b₂ :=
by cases r; reflexivity
definition eq_tr_of_pathover [unfold 8] (r : b =[p] b₂) : b = p⁻¹ ▸ b₂ :=
by cases r; reflexivity
definition pathover_equiv_tr_eq [constructor] (p : a = a₂) (b : B a) (b₂ : B a₂)
: (b =[p] b₂) ≃ (p ▸ b = b₂) :=
begin
fapply equiv.MK,
{ exact tr_eq_of_pathover},
{ exact pathover_of_tr_eq},
{ intro r, cases p, cases r, apply idp},
{ intro r, cases r, apply idp},
end
definition pathover_equiv_eq_tr [constructor] (p : a = a₂) (b : B a) (b₂ : B a₂)
: (b =[p] b₂) ≃ (b = p⁻¹ ▸ b₂) :=
begin
fapply equiv.MK,
{ exact eq_tr_of_pathover},
{ exact pathover_of_eq_tr},
{ intro r, cases p, cases r, apply idp},
{ intro r, cases r, apply idp},
end
definition pathover_tr [unfold 5] (p : a = a₂) (b : B a) : b =[p] p ▸ b :=
by cases p;constructor
definition tr_pathover [unfold 5] (p : a = a₂) (b : B a₂) : p⁻¹ ▸ b =[p] b :=
by cases p;constructor
definition concato [unfold 12] (r : b =[p] b₂) (r₂ : b₂ =[p₂] b₃) : b =[p ⬝ p₂] b₃ :=
pathover.rec_on r₂ r
definition inverseo [unfold 8] (r : b =[p] b₂) : b₂ =[p⁻¹] b :=
pathover.rec_on r idpo
definition apdo [unfold 6] (f : Πa, B a) (p : a = a₂) : f a =[p] f a₂ :=
eq.rec_on p idpo
definition concato_eq [unfold 10] (r : b =[p] b₂) (q : b₂ = b₂') : b =[p] b₂' :=
eq.rec_on q r
definition eq_concato [unfold 9] (q : b = b') (r : b' =[p] b₂) : b =[p] b₂ :=
by induction q;exact r
-- infix `⬝` := concato
infix `⬝o`:75 := concato
infix `⬝op`:75 := concato_eq
infix `⬝po`:75 := eq_concato
-- postfix `⁻¹` := inverseo
postfix `⁻¹ᵒ`:(max+10) := inverseo
/- Some of the theorems analogous to theorems for = in init.path -/
definition cono_idpo (r : b =[p] b₂) : r ⬝o idpo =[con_idp p] r :=
pathover.rec_on r idpo
definition idpo_cono (r : b =[p] b₂) : idpo ⬝o r =[idp_con p] r :=
pathover.rec_on r idpo
definition cono.assoc' (r : b =[p] b₂) (r₂ : b₂ =[p₂] b₃) (r₃ : b₃ =[p₃] b₄) :
r ⬝o (r₂ ⬝o r₃) =[!con.assoc'] (r ⬝o r₂) ⬝o r₃ :=
pathover.rec_on r₃ (pathover.rec_on r₂ (pathover.rec_on r idpo))
definition cono.assoc (r : b =[p] b₂) (r₂ : b₂ =[p₂] b₃) (r₃ : b₃ =[p₃] b₄) :
(r ⬝o r₂) ⬝o r₃ =[!con.assoc] r ⬝o (r₂ ⬝o r₃) :=
pathover.rec_on r₃ (pathover.rec_on r₂ (pathover.rec_on r idpo))
definition cono.right_inv (r : b =[p] b₂) : r ⬝o r⁻¹ᵒ =[!con.right_inv] idpo :=
pathover.rec_on r idpo
definition cono.left_inv (r : b =[p] b₂) : r⁻¹ᵒ ⬝o r =[!con.left_inv] idpo :=
pathover.rec_on r idpo
definition eq_of_pathover {a' a₂' : A'} (q : a' =[p] a₂') : a' = a₂' :=
by cases q;reflexivity
definition pathover_of_eq {a' a₂' : A'} (q : a' = a₂') : a' =[p] a₂' :=
by cases p;cases q;constructor
definition pathover_constant [constructor] (p : a = a₂) (a' a₂' : A') : a' =[p] a₂' ≃ a' = a₂' :=
begin
fapply equiv.MK,
{ exact eq_of_pathover},
{ exact pathover_of_eq},
{ intro r, cases p, cases r, reflexivity},
{ intro r, cases r, reflexivity},
end
definition eq_of_pathover_idp [unfold 6] {b' : B a} (q : b =[idpath a] b') : b = b' :=
tr_eq_of_pathover q
--should B be explicit in the next two definitions?
definition pathover_idp_of_eq [unfold 6] {b' : B a} (q : b = b') : b =[idpath a] b' :=
pathover_of_tr_eq q
definition pathover_idp [constructor] (b : B a) (b' : B a) : b =[idpath a] b' ≃ b = b' :=
equiv.MK eq_of_pathover_idp
(pathover_idp_of_eq)
(to_right_inv !pathover_equiv_tr_eq)
(to_left_inv !pathover_equiv_tr_eq)
-- definition pathover_idp (b : B a) (b' : B a) : b =[idpath a] b' ≃ b = b' :=
-- pathover_equiv_tr_eq idp b b'
-- definition eq_of_pathover_idp [reducible] {b' : B a} (q : b =[idpath a] b') : b = b' :=
-- to_fun !pathover_idp q
-- definition pathover_idp_of_eq [reducible] {b' : B a} (q : b = b') : b =[idpath a] b' :=
-- to_inv !pathover_idp q
definition idp_rec_on [recursor] {P : Π⦃b₂ : B a⦄, b =[idpath a] b₂ → Type}
{b₂ : B a} (r : b =[idpath a] b₂) (H : P idpo) : P r :=
have H2 : P (pathover_idp_of_eq (eq_of_pathover_idp r)), from
eq.rec_on (eq_of_pathover_idp r) H,
proof left_inv !pathover_idp r ▸ H2 qed
definition rec_on_right [recursor] {P : Π⦃b₂ : B a₂⦄, b =[p] b₂ → Type}
{b₂ : B a₂} (r : b =[p] b₂) (H : P !pathover_tr) : P r :=
by cases r; exact H
definition rec_on_left [recursor] {P : Π⦃b : B a⦄, b =[p] b₂ → Type}
{b : B a} (r : b =[p] b₂) (H : P !tr_pathover) : P r :=
by cases r; exact H
--pathover with fibration B' ∘ f
definition pathover_ap [unfold 10] (B' : A' → Type) (f : A → A') {p : a = a₂}
{b : B' (f a)} {b₂ : B' (f a₂)} (q : b =[p] b₂) : b =[ap f p] b₂ :=
by cases q; constructor
definition pathover_of_pathover_ap (B' : A' → Type) (f : A → A') {p : a = a₂}
{b : B' (f a)} {b₂ : B' (f a₂)} (q : b =[ap f p] b₂) : b =[p] b₂ :=
by cases p; apply (idp_rec_on q); apply idpo
definition pathover_compose [constructor] (B' : A' → Type) (f : A → A') (p : a = a₂)
(b : B' (f a)) (b₂ : B' (f a₂)) : b =[p] b₂ ≃ b =[ap f p] b₂ :=
begin
fapply equiv.MK,
{ apply pathover_ap},
{ apply pathover_of_pathover_ap},
{ intro q, cases p, esimp, apply (idp_rec_on q), apply idp},
{ intro q, cases q, reflexivity},
end
definition apdo_con (f : Πa, B a) (p : a = a₂) (q : a₂ = a₃)
: apdo f (p ⬝ q) = apdo f p ⬝o apdo f q :=
by cases p; cases q; reflexivity
definition apdo_inv (f : Πa, B a) (p : a = a₂) : apdo f p⁻¹ = (apdo f p)⁻¹ᵒ :=
by cases p; reflexivity
definition apdo_eq_pathover_of_eq_ap (f : A → A') (p : a = a₂) :
apdo f p = pathover_of_eq (ap f p) :=
eq.rec_on p idp
definition pathover_of_pathover_tr (q : b =[p ⬝ p₂] p₂ ▸ b₂) : b =[p] b₂ :=
by cases p₂;exact q
definition pathover_tr_of_pathover {p : a = a₃} (q : b =[p ⬝ p₂⁻¹] b₂) : b =[p] p₂ ▸ b₂ :=
by cases p₂;exact q
definition pathover_tr_of_eq (q : b = b') : b =[p] p ▸ b' :=
by cases q;apply pathover_tr
definition tr_pathover_of_eq (q : b₂ = b₂') : p⁻¹ ▸ b₂ =[p] b₂' :=
by cases q;apply tr_pathover
variable (C)
definition transporto (r : b =[p] b₂) (c : C b) : C b₂ :=
by induction r;exact c
infix `▸o`:75 := transporto _
definition fn_tro_eq_tro_fn (C' : Π ⦃a : A⦄, B a → Type) (q : b =[p] b₂)
(f : Π(b : B a), C b → C' b) (c : C b) : f b (q ▸o c) = (q ▸o (f b c)) :=
by induction q;reflexivity
variable {C}
definition apo {f : A → A'} (g : Πa, B a → B'' (f a))
(q : b =[p] b₂) : g a b =[p] g a₂ b₂ :=
by induction q; constructor
definition apo011 (f : Πa, B a → A') (Ha : a = a₂) (Hb : b =[Ha] b₂)
: f a b = f a₂ b₂ :=
by cases Hb; reflexivity
definition apo0111 (f : Πa b, C b → A') (Ha : a = a₂) (Hb : b =[Ha] b₂)
(Hc : c =[apo011 C Ha Hb] c₂) : f a b c = f a₂ b₂ c₂ :=
by cases Hb; apply (idp_rec_on Hc); apply idp
definition apo11 {f : Πb, C b} {g : Πb₂, C b₂} (r : f =[p] g)
{b : B a} {b₂ : B a₂} (q : b =[p] b₂) : f b =[apo011 C p q] g b₂ :=
by cases r; apply (idp_rec_on q); constructor
definition apdo10 {f : Πb, C b} {g : Πb₂, C b₂} (r : f =[p] g)
(b : B a) : f b =[apo011 C p !pathover_tr] g (p ▸ b) :=
by cases r; constructor
definition apo10 {f : B a → B' a} {g : B a₂ → B' a₂} (r : f =[p] g)
(b : B a) : f b =[p] g (p ▸ b) :=
by cases r; constructor
definition apdo_compose1 (g : Πa, B a → B' a) (f : Πa, B a) (p : a = a₂)
: apdo (g ∘' f) p = apo g (apdo f p) :=
by induction p; reflexivity
definition apdo_compose2 (g : Πa', B'' a') (f : A → A') (p : a = a₂)
: apdo (λa, g (f a)) p = pathover_of_pathover_ap B'' f (apdo g (ap f p)) :=
by induction p; reflexivity
definition cono.right_inv_eq (q : b = b')
: concato_eq (pathover_idp_of_eq q) q⁻¹ = (idpo : b =[refl a] b) :=
by induction q;constructor
definition cono.right_inv_eq' (q : b = b')
: eq_concato q (pathover_idp_of_eq q⁻¹) = (idpo : b =[refl a] b) :=
by induction q;constructor
definition cono.left_inv_eq (q : b = b')
: concato_eq (pathover_idp_of_eq q⁻¹) q = (idpo : b' =[refl a] b') :=
by induction q;constructor
definition cono.left_inv_eq' (q : b = b')
: eq_concato q⁻¹ (pathover_idp_of_eq q) = (idpo : b' =[refl a] b') :=
by induction q;constructor
definition change_path [unfold 9] (q : p = p') (r : b =[p] b₂) : b =[p'] b₂ :=
by induction q;exact r
definition change_path_equiv (f : Π{a}, B a ≃ B' a) (r : b =[p] b₂) : f b =[p] f b₂ :=
by induction r;constructor
definition change_path_equiv' (f : Π{a}, B a ≃ B' a) (r : f b =[p] f b₂) : b =[p] b₂ :=
(left_inv f b)⁻¹ ⬝po change_path_equiv (λa, f⁻¹ᵉ) r ⬝op left_inv f b₂
definition change_path_of_pathover (s : p = p') (r : b =[p] b₂) (r' : b =[p'] b₂)
(q : r =[s] r') : change_path s r = r' :=
by induction s; eapply idp_rec_on q; reflexivity
definition pathover_of_change_path (s : p = p') (r : b =[p] b₂) (r' : b =[p'] b₂)
(q : change_path s r = r') : r =[s] r' :=
by induction s; induction q; constructor
definition pathover_pathover_path [constructor] (s : p = p') (r : b =[p] b₂) (r' : b =[p'] b₂) :
(r =[s] r') ≃ change_path s r = r' :=
begin
fapply equiv.MK,
{ apply change_path_of_pathover},
{ apply pathover_of_change_path},
{ intro q, induction s, induction q, reflexivity},
{ intro q, induction s, eapply idp_rec_on q, reflexivity},
end
definition inverseo2 [unfold 10] {r r' : b =[p] b₂} (s : r = r') : r⁻¹ᵒ = r'⁻¹ᵒ :=
by induction s; reflexivity
definition concato2 [unfold 15 16] {r r' : b =[p] b₂} {r₂ r₂' : b₂ =[p₂] b₃}
(s : r = r') (s₂ : r₂ = r₂') : r ⬝o r₂ = r' ⬝o r₂' :=
by induction s; induction s₂; reflexivity
infixl `◾o`:75 := concato2
postfix [parsing-only] `⁻²ᵒ`:(max+10) := inverseo2 --this notation is abusive, should we use it?
end eq