[WIP] Proving other fusion law
Also set up framework for equality principle for monads
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@ -61,12 +61,21 @@ module Monoidal {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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isMonad : IsMonad raw
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open IsMonad isMonad public
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postulate propIsMonad : ∀ {raw} → isProp (IsMonad raw)
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Monad≡ : {m n : Monad} → Monad.raw m ≡ Monad.raw n → m ≡ n
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Monad.raw (Monad≡ eq i) = eq i
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Monad.isMonad (Monad≡ {m} {n} eq i) = res i
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where
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-- TODO: PathJ nightmare + `propIsMonad`.
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res : (λ i → IsMonad (eq i)) [ Monad.isMonad m ≡ Monad.isMonad n ]
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res = {!!}
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-- "A monad in the Kleisli form" [voe]
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module Kleisli {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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private
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ℓ = ℓa ⊔ ℓb
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open Category ℂ hiding (IsIdentity)
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open Category ℂ using (Arrow ; 𝟙 ; Object ; _∘_)
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record RawMonad : Set ℓ where
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field
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RR : Object → Object
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@ -87,6 +96,8 @@ module Kleisli {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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--
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pure : {X : Object} → ℂ [ X , RR X ]
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pure = ζ
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fmap : ∀ {A B} → ℂ [ A , B ] → ℂ [ RR A , RR B ]
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fmap f = rr (ζ ∘ f)
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-- Why is (>>=) not implementable?
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--
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-- (>>=) : m a -> (a -> m b) -> m b
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@ -101,25 +112,8 @@ module Kleisli {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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→ rr f ∘ ζ ≡ f
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IsDistributive = {X Y Z : Object} (g : ℂ [ Y , RR Z ]) (f : ℂ [ X , RR Y ])
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→ rr g ∘ rr f ≡ rr (rr g ∘ f)
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-- I assume `Fusion` is admissable - it certainly looks more like the
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-- distributive law for monads I know from Haskell.
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Fusion = {X Y Z : Object} (g : ℂ [ Y , Z ]) (f : ℂ [ X , Y ])
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→ rr (ζ ∘ g ∘ f) ≡ rr (ζ ∘ g) ∘ rr (ζ ∘ f)
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-- NatDist2Fus : IsNatural → IsDistributive → Fusion
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-- NatDist2Fus isNatural isDistributive g f =
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-- let
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-- ζf = ζ ∘ f
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-- ζg = ζ ∘ g
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-- Nζf : rr (ζ ∘ f) ∘ ζ ≡ ζ ∘ f
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-- Nζf = isNatural ζf
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-- Nζg : rr (ζ ∘ g) ∘ ζ ≡ ζ ∘ g
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-- Nζg = isNatural ζg
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-- ζgf = ζ ∘ g ∘ f
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-- Nζgf : rr (ζ ∘ g ∘ f) ∘ ζ ≡ ζ ∘ g ∘ f
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-- Nζgf = isNatural ζgf
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-- res : rr (ζ ∘ g ∘ f) ≡ rr (ζ ∘ g) ∘ rr (ζ ∘ f)
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-- res = {!!}
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-- in res
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Fusion = {X Y Z : Object} {g : ℂ [ Y , Z ]} {f : ℂ [ X , Y ]}
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→ fmap (g ∘ f) ≡ fmap g ∘ fmap f
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record IsMonad (raw : RawMonad) : Set ℓ where
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open RawMonad raw public
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@ -127,6 +121,16 @@ module Kleisli {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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isIdentity : IsIdentity
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isNatural : IsNatural
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isDistributive : IsDistributive
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fusion : Fusion
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fusion {g = g} {f} = begin
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fmap (g ∘ f) ≡⟨⟩
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rr (ζ ∘ (g ∘ f)) ≡⟨ {!!} ⟩
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rr (rr (ζ ∘ g) ∘ (ζ ∘ f)) ≡⟨ sym lem ⟩
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rr (ζ ∘ g) ∘ rr (ζ ∘ f) ≡⟨⟩
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fmap g ∘ fmap f ∎
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where
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lem : rr (ζ ∘ g) ∘ rr (ζ ∘ f) ≡ rr (rr (ζ ∘ g) ∘ (ζ ∘ f))
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lem = isDistributive (ζ ∘ g) (ζ ∘ f)
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record Monad : Set ℓ where
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field
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@ -134,6 +138,15 @@ module Kleisli {ℓa ℓb : Level} (ℂ : Category ℓa ℓb) where
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isMonad : IsMonad raw
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open IsMonad isMonad public
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postulate propIsMonad : ∀ {raw} → isProp (IsMonad raw)
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Monad≡ : {m n : Monad} → Monad.raw m ≡ Monad.raw n → m ≡ n
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Monad.raw (Monad≡ eq i) = eq i
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Monad.isMonad (Monad≡ {m} {n} eq i) = res i
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where
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-- TODO: PathJ nightmare + `propIsMonad`.
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res : (λ i → IsMonad (eq i)) [ Monad.isMonad m ≡ Monad.isMonad n ]
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res = {!!}
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-- Problem 2.3
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module _ {ℓa ℓb : Level} {ℂ : Category ℓa ℓb} where
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private
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@ -163,6 +176,7 @@ module _ {ℓa ℓb : Level} {ℂ : Category ℓa ℓb} where
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Kraw.rr forthRaw = rr
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module _ {raw : M.RawMonad} (m : M.IsMonad raw) where
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private
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open M.IsMonad m
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open K.RawMonad (forthRaw raw)
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module Kis = K.IsMonad
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@ -236,14 +250,76 @@ module _ {ℓa ℓb : Level} {ℂ : Category ℓa ℓb} where
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Kleisli.Monad.raw (forth m) = forthRaw (M.Monad.raw m)
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Kleisli.Monad.isMonad (forth m) = forthIsMonad (M.Monad.isMonad m)
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module _ (m : K.Monad) where
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private
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module ℂ = Category ℂ
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open K.Monad m
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module Mraw = M.RawMonad
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open NaturalTransformation ℂ ℂ
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rawR : RawFunctor ℂ ℂ
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RawFunctor.func* rawR = RR
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RawFunctor.func→ rawR f = rr (ζ ∘ f)
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isFunctorR : IsFunctor ℂ ℂ rawR
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IsFunctor.isIdentity isFunctorR = begin
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rr (ζ ∘ 𝟙) ≡⟨ cong rr (proj₁ ℂ.isIdentity) ⟩
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rr ζ ≡⟨ isIdentity ⟩
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𝟙 ∎
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IsFunctor.isDistributive isFunctorR {f = f} {g} = begin
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rr (ζ ∘ (g ∘ f)) ≡⟨⟩
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fmap (g ∘ f) ≡⟨ fusion ⟩
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fmap g ∘ fmap f ≡⟨⟩
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rr (ζ ∘ g) ∘ rr (ζ ∘ f) ∎
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R : Functor ℂ ℂ
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Functor.raw R = rawR
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Functor.isFunctor R = isFunctorR
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R2 : Functor ℂ ℂ
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R2 = F[ R ∘ R ]
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ηNat : NaturalTransformation F.identity R
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ηNat = {!!}
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μNat : NaturalTransformation R2 R
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μNat = {!!}
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backRaw : M.RawMonad
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Mraw.R backRaw = R
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Mraw.ηNat backRaw = ηNat
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Mraw.μNat backRaw = μNat
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module _ (m : K.Monad) where
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open K.Monad m
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open M.RawMonad (backRaw m)
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module Mis = M.IsMonad
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backIsMonad : M.IsMonad (backRaw m)
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backIsMonad = {!!}
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back : K.Monad → M.Monad
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back = {!!}
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Monoidal.Monad.raw (back m) = backRaw m
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Monoidal.Monad.isMonad (back m) = backIsMonad m
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forthRawEq : (m : K.Monad) → forthRaw (backRaw m) ≡ K.Monad.raw m
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K.RawMonad.RR (forthRawEq m _) = K.RawMonad.RR (K.Monad.raw m)
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K.RawMonad.ζ (forthRawEq m _) = K.RawMonad.ζ (K.Monad.raw m)
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-- stuck
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K.RawMonad.rr (forthRawEq m i) = {!!}
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fortheq : (m : K.Monad) → forth (back m) ≡ m
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fortheq m = {!!}
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fortheq m = K.Monad≡ (forthRawEq m)
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backRawEq : (m : M.Monad) → backRaw (forth m) ≡ M.Monad.raw m
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-- stuck
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M.RawMonad.R (backRawEq m _) = ?
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M.RawMonad.ηNat (backRawEq m x) = {!!}
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M.RawMonad.μNat (backRawEq m x) = {!!}
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backeq : (m : M.Monad) → back (forth m) ≡ m
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backeq = {!!}
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backeq m = M.Monad≡ (backRawEq m)
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open import Cubical.GradLemma
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eqv : isEquiv M.Monad K.Monad forth
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