view limit-to.agda @ 421:06ffcad985ac

fix free-monoid
author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Thu, 24 Mar 2016 12:07:32 +0900
parents 3e44951b9bdb
children 3a4a99a8edbe
line wrap: on
line source

open import Category -- https://github.com/konn/category-agda
open import Level

module limit-to where

open import cat-utility
open import HomReasoning
open import Relation.Binary.Core
open import Data.Maybe
open Functor




-- If we have limit then we have equalizer
---  two objects category
---
---          f
---       ------>
---     0         1
---       ------>
---          g



data  TwoObject {c₁ : Level}  : Set c₁ where
   t0 : TwoObject
   t1 : TwoObject

data Arrow {c₁ c₂ : Level } ( t00 t11 :  TwoObject {c₁} ) : TwoObject {c₁}  -> TwoObject {c₁} -> Set c₂ where
   id-t0 : Arrow t00 t11 t00 t00
   id-t1 : Arrow t00 t11 t11 t11
   arrow-f :  Arrow t00 t11 t00 t11
   arrow-g :  Arrow t00 t11 t00 t11
   inv-f :  Arrow t00 t11 t11 t00

record TwoHom {c₁ c₂ : Level} (a b : TwoObject {c₁}  ) : Set   c₂ where
   field
       RawHom   :   Maybe ( Arrow {c₁} {c₂} t0 t1 a b )

open TwoHom

hom :  ∀{ c₁ c₂ }  {  a b : TwoObject  {c₁} } ->
       ∀ (f :  TwoHom {c₁}  {c₂ } a b ) → Maybe ( Arrow {c₁} {c₂} t0 t1 a b )
hom {_} {_} {a} {b} f with RawHom  f
hom {_} {_} {t0} {t0} _ | just id-t0 = just id-t0
hom {_} {_} {t1} {t1} _ | just id-t1 = just id-t1
hom {_} {_} {t0} {t1} _ | just arrow-f = just arrow-f
hom {_} {_} {t0} {t1} _ | just arrow-g = just arrow-g
hom {_} {_} {t1} {t0} _ | just inv-f = just inv-f
hom {_} {_} {_ } {_ } _ | _ = nothing


open TwoHom

-- arrow composition


_×_ :  ∀ {c₁  c₂}  -> {a b c : TwoObject {c₁}} →  ( TwoHom {c₁}  {c₂} b c ) →  ( TwoHom {c₁} {c₂} a b )  →  ( TwoHom {c₁}  {c₂} a c )
_×_  {c₁}  {c₂}  {a} {b} {c} f g with hom f | hom g
_×_  {_}  {_}  {_} {_} {_} f g | nothing    | _                = record { RawHom =  nothing }
_×_  {_}  {_}  {_} {_} {_} f g | just _     | nothing          = record { RawHom =  nothing }
_×_  {_}  {_}  {t0} {t1} {t1} f g | just id-t1 | just arrow-f  = record { RawHom =  just arrow-f }
_×_  {_}  {_}  {t0} {t1} {t1} f g | just id-t1 | just arrow-g  = record { RawHom =  just arrow-g }
_×_  {_}  {_}  {t1} {t1} {t1} f g | just id-t1 | just id-t1    = record { RawHom =  just id-t1 }
_×_  {_}  {_}  {t1} {t1} {t0} f g | just inv-f | just id-t1    = record { RawHom =  just inv-f }
_×_  {_}  {_}  {t0} {t0} {t1} f g | just arrow-f | just id-t0    = record { RawHom =  just arrow-f }
_×_  {_}  {_}  {t0} {t0} {t1} f g | just arrow-g | just id-t0    = record { RawHom =  just arrow-g }
_×_  {_}  {_}  {t0} {t0} {t0} f g | just id-t0 | just id-t0    = record { RawHom =  just id-t0 }
_×_  {_}  {_}  {t1} {t0} {t0} f g | just id-t0 | just inv-f    = record { RawHom =  just inv-f }
_×_  {_}  {_}  {_} {_} {_} f g | just _ | just _   = record { RawHom =  nothing }


_==_ :  ∀{ c₁ c₂ a b }   ->  Rel (Maybe (Arrow {c₁} {c₂} t0 t1 a b )) (c₂)
_==_   =  Eq   _≡_

map2hom :  ∀{ c₁ c₂ } ->  {a b  : TwoObject {c₁}} →  Maybe ( Arrow  {c₁} {c₂} t0 t1 a b ) ->  TwoHom {c₁}  {c₂ } a b
map2hom {_} {_} {t1} {t1} (just id-t1)  = record { RawHom =  just id-t1 }
map2hom {_} {_} {t0} {t1} (just arrow-f) = record { RawHom =  just arrow-f }
map2hom {_} {_} {t0} {t1} (just arrow-g) = record { RawHom =  just arrow-g }
map2hom {_} {_} {t0} {t0} (just id-t0)   = record { RawHom =  just id-t0 }
map2hom {_} {_} {_} {_} _       = record { RawHom =  nothing }

record TwoHom1 {c₁ c₂ : Level}  (a : TwoObject {c₁}  ) (b : TwoObject {c₁}  ) : Set   c₂ where
   field
       Map       :   TwoHom {c₁}  {c₂ } a b
       iso-Map   :   Map ≡  map2hom ( hom Map )

==refl :  ∀{  c₁ c₂ a b }  ->  ∀ {x : Maybe (Arrow  {c₁} {c₂} t0 t1 a b )} → x == x
==refl {_} {_} {_} {_} {just x}  = just refl
==refl {_} {_} {_} {_} {nothing} = nothing

==sym :  ∀{  c₁ c₂ a b }   -> ∀ {x y :  Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )} →  x == y →  y == x
==sym (just x≈y) = just (≡-sym x≈y)
==sym nothing    = nothing

==trans :  ∀{  c₁ c₂ a b }   -> ∀ {x y z :   Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )  } →
         x == y → y == z  → x == z
==trans (just x≈y) (just y≈z) = just (≡-trans x≈y y≈z)
==trans nothing    nothing    = nothing

==cong :  ∀{  c₁ c₂ a b }   -> ∀ {x y :  Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )} →  
        (f : Maybe (Arrow  {c₁}  {c₂} t0 t1 a b ) -> Maybe (Arrow  {c₁}  {c₂} t0 t1 a b ) ) -> x  ≡  y →  f x == f y
==cong f refl = ==refl


module ==-Reasoning {c₁ c₂ : Level} where

        infixr  2 _∎
        infixr 2 _==⟨_⟩_ _==⟨⟩_
        infix  1 begin_


        data _IsRelatedTo_   {c₁ c₂ : Level}  {a b : TwoObject {c₁}  }  (x y : (Maybe (Arrow  {c₁}  {c₂} t0 t1 a b ))) :
                             Set  c₂ where
            relTo : (x≈y : x  == y  ) → x IsRelatedTo y

        begin_ :  { a b : TwoObject  {c₁} } {x : Maybe (Arrow  {c₁}  {c₂} t0 t1 a b ) } {y : Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )} →
                   x IsRelatedTo y →  x ==  y
        begin relTo x≈y = x≈y

        _==⟨_⟩_ :  { a b : TwoObject  {c₁} } (x :  Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )) {y z :  Maybe (Arrow  {c₁}  {c₂} t0 t1 a b ) } →
                    x == y  → y IsRelatedTo z → x IsRelatedTo z
        _ ==⟨ x≈y ⟩ relTo y≈z = relTo (==trans x≈y y≈z)

        _==⟨⟩_ :   { a b : TwoObject  {c₁} }(x : Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )) {y : Maybe (Arrow  {c₁}  {c₂} t0 t1 a b  )}
                    → x IsRelatedTo y → x IsRelatedTo y
        _ ==⟨⟩ x≈y = x≈y

        _∎ :   { a b : TwoObject  {c₁} }(x :  Maybe (Arrow  {c₁}  {c₂} t0 t1 a b )) → x IsRelatedTo x
        _∎ _ = relTo ==refl



--          f    g    h
--       d <- c <- b <- a
--
--   It can be proved without Arrow constraints

assoc-× :   {c₁  c₂ : Level } {a b c d : TwoObject  {c₁} }
       {f : (TwoHom {c₁}  {c₂ } c d )} →
       {g : (TwoHom {c₁}  {c₂ } b c )} →
       {h : (TwoHom {c₁}  {c₂ } a b )} →
       hom ( f × (g × h)) == hom ((f × g) × h )
assoc-× {c₁} {c₂} {a} {b} {c} {d} {f} {g} {h} with  hom f | hom g | hom h
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t0} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t0} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t0} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t0} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t0} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t1} {f} {g} {h} | nothing | _ | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t0} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t0} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t0} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t0} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t0} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t1} {f} {g} {h} | just _ | nothing | _ = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t0} {f} {g} {h} | just id-t0   | just id-t0   | just id-t0  = ==refl
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | just arrow-f | just id-t0   | just id-t0  = ==refl
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | just arrow-g | just id-t0   | just id-t0  = ==refl
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | just id-t1   | just arrow-f | just id-t0  = ==refl
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | just id-t1   | just arrow-g | just id-t0  = ==refl
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t1} {f} {g} {h} | just id-t1   | just id-t1   | just arrow-f = ==refl
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t1} {f} {g} {h} | just id-t1   | just id-t1   | just arrow-g = ==refl
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t1} {f} {g} {h} | just id-t1   | just id-t1   | just id-t1  = ==refl
--  remaining all failure case
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t0} {f} {g} {h} | just id-t0 | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t0} {f} {g} {h} | just id-t0 | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t1} {f} {g} {h} | just id-t1 | just id-t1 | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t1} {f} {g} {h} | just id-t1 | just id-t1 | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t0} {t0} {f} {g} {h} | just id-t0 | just inv-f | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t0} {t0} {f} {g} {h} | just id-t0 | just inv-f | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t1} {f} {g} {h} | just arrow-f | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t0} {t1} {f} {g} {h} | just arrow-g | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | just arrow-f | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t0} {t1} {f} {g} {h} | just arrow-g | just id-t0 | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | just id-t1 | just arrow-f | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t0} {t1} {t1} {f} {g} {h} | just id-t1 | just arrow-g | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t1} {f} {g} {h} | just id-t1 | just arrow-f | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t0} {t1} {t1} {f} {g} {h} | just id-t1 | just arrow-g | nothing = nothing
assoc-× {c₁} {c₂} {t0} {t1} {t1} {t0} {f} {g} {h} | just inv-f | just id-t1 | nothing = nothing
assoc-× {c₁} {c₂} {t1} {t1} {t1} {t0} {f} {g} {h} | just inv-f | just id-t1 | nothing = nothing
assoc-× {_} {_} {t0} {t0} {t1} {t0} {_} {_} {_} | (just _) | (just _) | nothing = nothing
assoc-× {_} {_} {t0} {t1} {t0} {t1} {_} {_} {_} | (just _) | (just _) | nothing = nothing
assoc-× {_} {_} {t1} {t0} {t1} {t0} {_} {_} {_} | (just _) | (just _) | nothing = nothing
assoc-× {_} {_} {t1} {t1} {t0} {t1} {_} {_} {_} | (just _) | (just _) | nothing = nothing
assoc-× {_} {_} {t0} {t0} {t1} {t0} {_} {_} {_} | (just _) | (just arrow-f) | (just id-t0) = nothing
assoc-× {_} {_} {t0} {t0} {t1} {t0} {_} {_} {_} | (just _) | (just arrow-g) | (just id-t0) = nothing
assoc-× {_} {_} {t0} {t1} {t0} {t0} {_} {_} {_} | (just id-t0) | (just inv-f) | (just _) = nothing
assoc-× {_} {_} {t0} {t1} {t0} {t1} {_} {_} {_} | (just _) | (just _) | (just _) = nothing
assoc-× {_} {_} {t0} {t1} {t1} {t0} {_} {_} {_} | (just inv-f) | (just id-t1) | (just arrow-f) = nothing
assoc-× {_} {_} {t0} {t1} {t1} {t0} {_} {_} {_} | (just inv-f) | (just id-t1) | (just arrow-g) = nothing
assoc-× {_} {_} {t1} {t0} {t0} {t0} {_} {_} {_} | (just id-t0) | (just id-t0) | (just inv-f) = ==refl
assoc-× {_} {_} {t1} {t0} {t0} {t1} {_} {_} {_} | (just arrow-f) | (just id-t0) | (just inv-f) = nothing
assoc-× {_} {_} {t1} {t0} {t0} {t1} {_} {_} {_} | (just arrow-g) | (just id-t0) | (just inv-f) = nothing
assoc-× {_} {_} {t1} {t0} {t1} {t0} {_} {_} {_} | (just _) | (just _) | (just _) = nothing
assoc-× {_} {_} {t1} {t0} {t1} {t1} {_} {_} {_} | (just id-t1) | (just arrow-f) | (just _) = nothing
assoc-× {_} {_} {t1} {t0} {t1} {t1} {_} {_} {_} | (just id-t1) | (just arrow-g) | (just _) = nothing
assoc-× {_} {_} {t1} {t1} {t0} {t0} {_} {_} {_} | (just id-t0) | (just inv-f) | (just id-t1) = ==refl
assoc-× {_} {_} {t1} {t1} {t0} {t1} {_} {_} {_} | (just arrow-f) | (just inv-f) | (just id-t1) = ==refl
assoc-× {_} {_} {t1} {t1} {t0} {t1} {_} {_} {_} | (just arrow-g) | (just inv-f) | (just id-t1) = ==refl
assoc-× {_} {_} {t1} {t1} {t1} {t0} {_} {_} {_} | (just inv-f) | (just id-t1) | (just id-t1) = ==refl



TwoId :  {c₁  c₂ : Level } (a : TwoObject  {c₁} ) ->  (TwoHom {c₁}  {c₂ } a a )
TwoId {_} {_} t0 = record { RawHom =  just id-t0 }
TwoId {_} {_} t1 = record { RawHom =  just id-t1 }

open import maybeCat

--        identityL  {c₁}  {c₂}  {_} {b} {nothing}  =   let open ==-Reasoning  {c₁}  {c₂} in
--                begin
--                   (TwoId b × nothing)
--                ==⟨ {!!}  ⟩
--                  nothing
--                ∎

open import Relation.Binary
TwoCat : {c₁ c₂ ℓ : Level  } ->  Category   c₁  c₂  c₂
TwoCat   {c₁}  {c₂} {ℓ} = record {
    Obj  = TwoObject  {c₁} ;
    Hom = λ a b →    ( TwoHom {c₁}  {c₂ } a b ) ;
    _o_ =  \{a} {b} {c} x y -> _×_ {c₁ } { c₂} {a} {b} {c} x y ;
    _≈_ =  \x y -> hom x == hom y ;
    Id  =  \{a} -> TwoId {c₁ } { c₂} a ;
    isCategory  = record {
            isEquivalence =  record {refl = ==refl ; trans = ==trans ; sym = ==sym } ;
            identityL  = \{a b f} -> identityL {c₁}  {c₂ } {a} {b} {f} ;
            identityR  = \{a b f} -> identityR {c₁}  {c₂ } {a} {b} {f} ;
            o-resp-≈  = \{a b c f g h i} ->  o-resp-≈  {c₁}  {c₂ } {a} {b} {c} {f} {g} {h} {i} ;
            associative  = \{a b c d f g h } -> assoc-×   {c₁}  {c₂} {a} {b} {c} {d} {f} {g} {h}
       }
   }  where
        identityL :  {c₁  c₂ : Level } {A B : TwoObject {c₁}} {f : ( TwoHom {c₁}  {c₂ } A B) } →  hom ((TwoId B)  × f)  == hom f
        identityL  {c₁}  {c₂}  {_} {_} {f}  with hom f
        identityL  {c₁}  {c₂}  {t0} {t0} {_} | nothing  = nothing
        identityL  {c₁}  {c₂}  {t0} {t1} {_} | nothing  = nothing
        identityL  {c₁}  {c₂}  {t1} {t0} {_} | nothing  = nothing
        identityL  {c₁}  {c₂}  {t1} {t1} {_} | nothing  = nothing
        identityL  {c₁}  {c₂}  {t1} {t0} {_} | just inv-f  = ==refl
        identityL  {c₁}  {c₂}  {t1} {t1} {_} | just id-t1  = ==refl
        identityL  {c₁}  {c₂}  {t0} {t0} {_} | just id-t0 = ==refl
        identityL  {c₁}  {c₂}  {t0} {t1} {_} | just arrow-f = ==refl
        identityL  {c₁}  {c₂}  {t0} {t1} {_} | just arrow-g = ==refl
        identityR :  {c₁  c₂ : Level } {A B : TwoObject {c₁}} {f : ( TwoHom {c₁}  {c₂ } A B) } →   hom ( f × TwoId A )  == hom f
        identityR  {c₁}  {c₂}  {_} {_} {f}  with hom f
        identityR  {c₁}  {c₂}  {t0} {t0} {_} | nothing  = nothing
        identityR  {c₁}  {c₂}  {t0} {t1} {_} | nothing  = nothing
        identityR  {c₁}  {c₂}  {t1} {t0} {_} | nothing  = nothing
        identityR  {c₁}  {c₂}  {t1} {t1} {_} | nothing  = nothing
        identityR  {c₁}  {c₂}  {t1} {t0} {_} | just inv-f  = ==refl
        identityR  {c₁}  {c₂}  {t1} {t1} {_} | just id-t1  = ==refl
        identityR  {c₁}  {c₂}  {t0} {t0} {_} | just id-t0 = ==refl
        identityR  {c₁}  {c₂}  {t0} {t1} {_} | just arrow-f = ==refl
        identityR  {c₁}  {c₂}  {t0} {t1} {_} | just arrow-g = ==refl
        o-resp-≈ :  {c₁  c₂ : Level } {A B C : TwoObject  {c₁} } {f g :  ( TwoHom {c₁}  {c₂ } A B)} {h i : ( TwoHom B C)} →
            hom f == hom g → hom h == hom i → hom ( h × f ) == hom ( i × g )
        o-resp-≈  {c₁}  {c₂} {a} {b} {c} {f} {g} {h} {i}  f≡g h≡i  with hom f | hom g | hom h | hom i
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  nothing nothing | nothing | nothing | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  f≡g nothing | just _ | just _ | nothing | nothing  = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g (just refl) | nothing | just _ | just jh | just .jh = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g (just refl) | just _ | nothing | just jh | just .jh = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  (just refl) h≡i | just jf | just .jf | nothing | just _ = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  (just refl) h≡i | just jf | just .jf | just _ | nothing = {!!}
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  f≡g h≡i | just id-t0 | nothing | just id-t0 | nothing = ?
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | just _ | nothing | just _ | nothing = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | nothing | just _ | just _ | nothing = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | nothing | just _ | nothing | just _ = {!!}
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | just _ | nothing | nothing | just _ = {!!}
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | nothing | just _ = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  nothing h≡i | nothing | nothing | just _ | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  f≡g nothing | nothing | just _ | nothing | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | nothing | just _ | nothing | nothing = {!!}
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  f≡g nothing | just _ | nothing | nothing | nothing = nothing
        o-resp-≈  {c₁}  {c₂} {_} {_} {_} {f} {g} {h} {i}  f≡g h≡i | just _ | nothing | nothing | nothing = {!!}
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t0} {f} {g} {h} {i}  (just refl) (just refl) | just id-t0 | just id-t0 | just id-t0  | just id-t0   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just id-t1 | just id-t1 | just id-t1  | just id-t1   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just arrow-f | just arrow-f | just id-t1  | just id-t1   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just arrow-g | just arrow-g | just id-t1  | just id-t1   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just id-t0 | just id-t0 | just arrow-f | just arrow-f  =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t0} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just id-t0 | just id-t0 | just arrow-g | just arrow-g  =  ==refl
        o-resp-≈  {c₁}  {c₂} {t1} {t1} {t0} {f} {g} {h} {i}  (just refl) (just refl) | just id-t1 | just id-t1 | just inv-f | just inv-f  =  ==refl
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t0} {f} {g} {h} {i}  (just refl) (just refl) | just inv-f | just inv-f | just id-t0  | just id-t0   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just inv-f | just inv-f | just arrow-f  | just arrow-f   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t1} {t0} {t1} {f} {g} {h} {i}  (just refl) (just refl) | just inv-f | just inv-f | just arrow-g  | just arrow-g   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  (just refl) (just refl) | just arrow-f | just arrow-f | just inv-f  | just inv-f   =  ==refl
        o-resp-≈  {c₁}  {c₂} {t0} {t1} {t0} {f} {g} {h} {i}  (just refl) (just refl) | just arrow-g | just arrow-g | just inv-f  | just inv-f   =  ==refl
--        o-resp-≈  {c₁}  {c₂} {a} {b} {c} {f} {g} {h} {i}  (just refl) (just refl) | just jf | just .jf | just jh  | just .jh   =  
--          let open  ==-Reasoning {c₁} {c₂ } in begin
--                   {!!}
--                ==⟨ {!!} ⟩
--                   {!!}
--                ∎



indexFunctor :  {c₁ c₂ ℓ : Level} (A : Category c₁ c₂ ℓ) ( a b : Obj (MaybeCat A )) ( f g : Hom A a b ) ->  Functor (TwoCat {c₁} {c₂} {c₂} ) (MaybeCat A )
indexFunctor  {c₁} {c₂} {ℓ} A  a b f g = record {
         FObj = λ a → fobj a
       ; FMap = λ {a} {b} f → fmap {a} {b} f
       ; isFunctor = record {
             identity = \{x} -> identity {x}
             ; distr = \ {a} {b} {c} {f} {g}   -> distr1 {a} {b} {c} {f} {g}
             ; ≈-cong = \ {a} {b} {c} {f}   -> ≈-cong  {a} {b} {c} {f}
       }
      } where
          I = TwoCat  {c₁} {c₂} {ℓ}
          MA = MaybeCat A
          open ≈-Reasoning (MA)
          fobj :  Obj I -> Obj A
          fobj t0 = a
          fobj t1 = b
          fmap :  {x y : Obj I } ->  (TwoHom {c₁}  {c₂} x y  ) -> Hom MA (fobj x) (fobj y)
          fmap  {x} {y} h with hom h
          fmap  {t0} {t0} h | just id-t0 = id1 MA a
          fmap  {t1} {t1} h | just id-t1 = id1 MA b
          fmap  {t0} {t1} h | just arrow-f = record { hom = just f }
          fmap  {t0} {t1} h | just arrow-g = record { hom = just g }
          fmap  {_} {_} h | _  = record { hom = nothing }
          identity :  {x : Obj I} → MA [ fmap ( id1 I x ) ≈  id1 MA (fobj x) ]
          identity {t0}  =  refl-hom
          identity {t1}  =  refl-hom
          distr1 : {a₁ : Obj I} {b₁ : Obj I} {c : Obj I} {f₁ : Hom I a₁ b₁} {g₁ : Hom I b₁ c} →
               MA [ fmap (I [ g₁ o f₁ ])  ≈  MA [ fmap g₁ o fmap f₁ ] ]
          distr1 {a1} {b1} {c1} {f1} {g1}   with hom g1 | hom f1
          distr1 {t0} {t0} {t0} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t0} {t0} {t1} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t0} {t1} {t0} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t0} {t1} {t1} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t1} {t0} {t0} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t1} {t0} {t1} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t1} {t1} {t0} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t1} {t1} {t1} {f1} {g1} | nothing | nothing   =  nothing
          distr1 {t0} {t0} {t0} {f1} {g1} | nothing | just id-t0   =  nothing
          distr1 {t0} {t0} {t1} {f1} {g1} | nothing | just id-t0   =  nothing
          distr1 {t1} {t1} {t0} {f1} {g1} | nothing | just id-t1   =  nothing
          distr1 {t1} {t1} {t1} {f1} {g1} | nothing | just id-t1   =  nothing
          distr1 {t0} {t1} {t1} {f1} {g1} | nothing | just arrow-f   =  nothing
          distr1 {t0} {t1} {t0} {f1} {g1} | nothing | just arrow-f   =  nothing
          distr1 {t0} {t1} {t1} {f1} {g1} | nothing | just arrow-g   =  nothing
          distr1 {t0} {t1} {t0} {f1} {g1} | nothing | just arrow-g   =  nothing
          distr1 {t1} {t0} {t0} {f1} {g1} | nothing | just inv-f   =  nothing
          distr1 {t1} {t0} {t1} {f1} {g1} | nothing | just inv-f   =  nothing
          distr1 {t0} {t0} {t0} {f1} {g1} | just id-t0 | nothing    = nothing
          distr1 {t1} {t0} {t0} {f1} {g1} | just id-t0 | nothing    = nothing
          distr1 {t0} {t1} {t1} {f1} {g1} | just id-t1 | nothing    = nothing
          distr1 {t1} {t1} {t1} {f1} {g1} | just id-t1 | nothing    = nothing
          distr1 {t0} {t0} {t1} {f1} {g1} | just arrow-f | nothing    = nothing
          distr1 {t1} {t0} {t1} {f1} {g1} | just arrow-f | nothing    = nothing
          distr1 {t0} {t0} {t1} {f1} {g1} | just arrow-g | nothing    = nothing
          distr1 {t1} {t0} {t1} {f1} {g1} | just arrow-g | nothing    = nothing
          distr1 {t0} {t1} {t0} {f1} {g1} | just inv-f | nothing    = nothing
          distr1 {t1} {t1} {t0} {f1} {g1} | just inv-f | nothing    = nothing
          distr1 {t0} {t0} {t0} {f1} {g1} | just id-t0 | just id-t0   = sym idL
          distr1 {t1} {t0} {t0} {f1} {g1} | just id-t0 | just inv-f   = sym idL
          distr1 {t0} {t0} {t1} {f1} {g1} | just arrow-f | just id-t0   = sym idR
          distr1 {t0} {t0} {t1} {f1} {g1} | just arrow-g | just id-t0   = sym idR
          distr1 {t1} {t1} {t1} {f1} {g1} | just id-t1 | just id-t1   = sym idL
          distr1 {t0} {t1} {t1} {f1} {g1} | just id-t1 | just arrow-f   = sym idL
          distr1 {t0} {t1} {t1} {f1} {g1} | just id-t1 | just arrow-g   = sym idL
          distr1 {t1} {t1} {t0} {f1} {g1} | just inv-f | just id-t1   = sym idL
          distr1 {t0} {t1} {t0} {_} {_} | (just inv-f) | (just _) = nothing
          distr1 {t1} {t0} {t1} {_} {_} | (just arrow-f) |  (just _) = nothing
          distr1 {t1} {t0} {t1} {_} {_} | (just arrow-g) |  (just _) = nothing

          ≈-cong :   {a : Obj I} {b : Obj I} {f g : Hom I a b}  → I [ f ≈ g ]  → MA [ fmap f ≈ fmap g ]
          ≈-cong   {_} {_} {f1} {g1} f≈g with hom f1 | hom  g1
          ≈-cong   {t0} {t0} {f1} {g1} f≈g | nothing | nothing = nothing
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | nothing | nothing = nothing
          ≈-cong   {t1} {t0} {f1} {g1} f≈g | nothing | nothing = nothing
          ≈-cong   {t1} {t1} {f1} {g1} f≈g | nothing | nothing = nothing
          ≈-cong   {t0} {t0} {f1} {g1} f≈g | nothing | just id-t0 =  {!!}
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | nothing | just arrow-f = {!!}
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | nothing | just arrow-g = {!!}
          ≈-cong   {t1} {t0} {f1} {g1} f≈g | nothing | just inv-f = nothing
          ≈-cong   {t1} {t1} {f1} {g1} f≈g | nothing | just id-t1 = {!!}
          ≈-cong   {t0} {t0} {f1} {g1} f≈g | just id-t0 | nothing  = {!!}
          ≈-cong   {t1} {t1} {f1} {g1} f≈g | just id-t1 | nothing  = {!!}
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-f | nothing  = {!!}
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-g | nothing  = {!!}
          ≈-cong   {t1} {t0} {f1} {g1} f≈g | just inv-f | nothing  = nothing
          ≈-cong   {t0} {t0} {f1} {g1} f≈g | just id-t0 | just id-t0 = refl-hom
          ≈-cong   {t1} {t1} {f1} {g1} f≈g | just id-t1 | just id-t1 = refl-hom
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-f | just arrow-f = refl-hom
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-g | just arrow-g = refl-hom
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-g | just arrow-f = {!!}
          ≈-cong   {t1} {t0} {f1} {g1} f≈g | just inv-f | just inv-f = refl-hom
          ≈-cong   {t0} {t1} {f1} {g1} f≈g | just arrow-f | just arrow-g = begin
                     {!!}
                 ≈⟨ {!!} ⟩
                     {!!}



---  Equalizer
---                     f
---          e       ------>
---     c ------>  a         b
---     ^      /     ------>
---     |k   h          g
---     |   /
---     |  /
---     | /
---     |/
---     d

open Limit

lim-to-equ :  {c₁ c₂ ℓ : Level} (A : Category c₁ c₂ ℓ)  ->
      (lim : (I : Category c₁ c₂ ℓ) ( Γ : Functor I A ) → {a0 : Obj A } {u : NTrans I A ( K A I a0 ) Γ } → Limit A I Γ a0 u ) -- completeness
        →  {a b c : Obj A}      (f g : Hom A  a b )
        → (e : Hom A c a ) → (fe=ge : A [ A [ f o e ] ≈ A [ g o e ] ] ) → Equalizer A e f g
lim-to-equ  {c₁} {c₂} {ℓ } A  lim {a} {b} {c}  f g e fe=ge = record {
        fe=ge =  fe=ge
        ; k = λ {d} h fh=gh → k {d} h fh=gh
        ; ek=h = λ {d} {h} {fh=gh} → ek=h d h fh=gh
        ; uniqueness = λ {d} {h} {fh=gh} {k'} → uniquness d h fh=gh k'
     } where
         I = TwoCat {c₁} {c₂} {ℓ }
         Γ = {!!}
         nmap :  (x : Obj I) ( d : Obj A ) (h : Hom A d a ) -> Hom A (FObj (K A I d) x) (FObj Γ x)
         nmap x d h = {!!}
         commute1 : {x y : Obj I}  {f' : Hom I x y} (d : Obj A) (h : Hom A d a ) ->  A [ A [ f  o  h ] ≈ A [ g  o h ] ]
                 → A [ A [ FMap Γ f' o nmap x d h ] ≈ A [ nmap y d h o FMap (K A I d) f' ] ]
         commute1  {x} {y} {f'} d h fh=gh = {!!}
         nat : (d : Obj A) → (h : Hom A d a ) →  A [ A [ f  o  h ] ≈ A [ g  o h ] ]   → NTrans I A (K A I d) Γ
         nat d h fh=gh = record {
            TMap = λ x → nmap x d h ;
            isNTrans = record {
                commute = λ {x} {y} {f'} -> commute1 {x} {y} {f'} d h fh=gh
            }
          }
         k : {d : Obj A}  (h : Hom A d a) → A [ A [ f  o  h ] ≈ A [ g  o h ] ] → Hom A d c
         k {d} h fh=gh  = {!!} -- limit (lim I Γ  {c} {nat c e fe=ge }) d (nat d h fh=gh )
         ek=h :  (d : Obj A ) (h : Hom A d a ) ->  ( fh=gh : A [ A [ f  o  h ] ≈ A [ g  o h ] ] )  -> A [ A [ e o k h fh=gh ] ≈ h ]
         ek=h d h fh=gh = {!!}
         uniquness :  (d : Obj A ) (h : Hom A d a ) ->  ( fh=gh : A [ A [ f  o  h ] ≈ A [ g  o h ] ] )  ->
                 ( k' : Hom A d c )
                -> A [ A [ e o k' ] ≈ h ] → A [ k h fh=gh ≈ k' ]
         uniquness d h fh=gh = {!!}