236 lines
9.3 KiB
Agda
236 lines
9.3 KiB
Agda
module Lattice where
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import Data.Nat.Properties as NatProps
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open import Relation.Binary.PropositionalEquality as Eq using (_≡_; sym)
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open import Relation.Binary.Definitions
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open import Data.Nat as Nat using (ℕ; _≤_)
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open import Data.Product using (_×_; _,_)
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open import Data.Sum using (_⊎_; inj₁; inj₂)
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open import Agda.Primitive using (lsuc; Level)
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open import NatMap using (NatMap)
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record IsPreorder {a} (A : Set a) (_≼_ : A → A → Set a) : Set a where
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field
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≼-refl : Reflexive (_≼_)
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≼-trans : Transitive (_≼_)
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≼-antisym : Antisymmetric (_≡_) (_≼_)
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isPreorderFlip : {a : Level} → {A : Set a} → {_≼_ : A → A → Set a} → IsPreorder A _≼_ → IsPreorder A (λ x y → y ≼ x)
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isPreorderFlip isPreorder = record
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{ ≼-refl = IsPreorder.≼-refl isPreorder
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; ≼-trans = λ {x} {y} {z} x≽y y≽z → IsPreorder.≼-trans isPreorder y≽z x≽y
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; ≼-antisym = λ {x} {y} x≽y y≽x → IsPreorder.≼-antisym isPreorder y≽x x≽y
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}
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record Preorder {a} (A : Set a) : Set (lsuc a) where
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field
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_≼_ : A → A → Set a
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isPreorder : IsPreorder A _≼_
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open IsPreorder isPreorder public
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record IsSemilattice {a} (A : Set a) (_≼_ : A → A → Set a) (_⊔_ : A → A → A) : Set a where
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field
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isPreorder : IsPreorder A _≼_
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⊔-assoc : (x y z : A) → (x ⊔ y) ⊔ z ≡ x ⊔ (y ⊔ z)
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⊔-comm : (x y : A) → x ⊔ y ≡ y ⊔ x
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⊔-idemp : (x : A) → x ⊔ x ≡ x
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⊔-bound : (x y z : A) → x ⊔ y ≡ z → (x ≼ z × y ≼ z)
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⊔-least : (x y z : A) → x ⊔ y ≡ z → ∀ (z' : A) → (x ≼ z' × y ≼ z') → z ≼ z'
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open IsPreorder isPreorder public
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record Semilattice {a} (A : Set a) : Set (lsuc a) where
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field
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_≼_ : A → A → Set a
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_⊔_ : A → A → A
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isSemilattice : IsSemilattice A _≼_ _⊔_
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open IsSemilattice isSemilattice public
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record IsLattice {a} (A : Set a) (_≼_ : A → A → Set a) (_⊔_ : A → A → A) (_⊓_ : A → A → A) : Set a where
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_≽_ : A → A → Set a
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a ≽ b = b ≼ a
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field
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joinSemilattice : IsSemilattice A _≼_ _⊔_
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meetSemilattice : IsSemilattice A _≽_ _⊓_
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absorb-⊔-⊓ : (x y : A) → x ⊔ (x ⊓ y) ≡ x
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absorb-⊓-⊔ : (x y : A) → x ⊓ (x ⊔ y) ≡ x
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open IsSemilattice joinSemilattice public
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open IsSemilattice meetSemilattice public renaming
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( ⊔-assoc to ⊓-assoc
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; ⊔-comm to ⊓-comm
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; ⊔-idemp to ⊓-idemp
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; ⊔-bound to ⊓-bound
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; ⊔-least to ⊓-least
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)
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record Lattice {a} (A : Set a) : Set (lsuc a) where
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field
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_≼_ : A → A → Set a
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_⊔_ : A → A → A
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_⊓_ : A → A → A
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isLattice : IsLattice A _≼_ _⊔_ _⊓_
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open IsLattice isLattice public
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module PreorderInstances where
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module ForNat where
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open NatProps
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NatPreorder : Preorder ℕ
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NatPreorder = record
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{ _≼_ = _≤_
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; isPreorder = record
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{ ≼-refl = ≤-refl
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; ≼-trans = ≤-trans
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; ≼-antisym = ≤-antisym
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}
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}
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module ForProd {a} {A B : Set a} {{ pA : Preorder A }} {{ pB : Preorder B }} where
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open Eq
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private
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_≼_ : A × B → A × B → Set a
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(a₁ , b₁) ≼ (a₂ , b₂) = Preorder._≼_ pA a₁ a₂ × Preorder._≼_ pB b₁ b₂
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ispA = Preorder.isPreorder pA
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ispB = Preorder.isPreorder pB
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≼-refl : {p : A × B} → p ≼ p
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≼-refl {(a , b)} = (IsPreorder.≼-refl ispA {a}, IsPreorder.≼-refl ispB {b})
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≼-trans : {p₁ p₂ p₃ : A × B} → p₁ ≼ p₂ → p₂ ≼ p₃ → p₁ ≼ p₃
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≼-trans (a₁≼a₂ , b₁≼b₂) (a₂≼a₃ , b₂≼b₃) =
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( IsPreorder.≼-trans ispA a₁≼a₂ a₂≼a₃
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, IsPreorder.≼-trans ispB b₁≼b₂ b₂≼b₃
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)
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≼-antisym : {p₁ p₂ : A × B} → p₁ ≼ p₂ → p₂ ≼ p₁ → p₁ ≡ p₂
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≼-antisym (a₁≼a₂ , b₁≼b₂) (a₂≼a₁ , b₂≼b₁) = cong₂ (_,_) (IsPreorder.≼-antisym ispA a₁≼a₂ a₂≼a₁) (IsPreorder.≼-antisym ispB b₁≼b₂ b₂≼b₁)
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ProdPreorder : Preorder (A × B)
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ProdPreorder = record
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{ _≼_ = _≼_
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; isPreorder = record
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{ ≼-refl = ≼-refl
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; ≼-trans = ≼-trans
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; ≼-antisym = ≼-antisym
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}
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}
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private module NatInstances where
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open Nat
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open NatProps
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open Eq
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open PreorderInstances.ForNat
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private
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max-bound₁ : {x y z : ℕ} → x ⊔ y ≡ z → x ≤ z
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max-bound₁ {x} {y} {z} x⊔y≡z rewrite sym x⊔y≡z rewrite ⊔-comm x y = m≤n⇒m≤o⊔n y (≤-refl)
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max-bound₂ : {x y z : ℕ} → x ⊔ y ≡ z → y ≤ z
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max-bound₂ {x} {y} {z} x⊔y≡z rewrite sym x⊔y≡z = m≤n⇒m≤o⊔n x (≤-refl)
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max-least : (x y z : ℕ) → x ⊔ y ≡ z → ∀ (z' : ℕ) → (x ≤ z' × y ≤ z') → z ≤ z'
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max-least x y z x⊔y≡z z' (x≤z' , y≤z') with (⊔-sel x y)
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... | inj₁ x⊔y≡x rewrite trans (sym x⊔y≡z) (x⊔y≡x) = x≤z'
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... | inj₂ x⊔y≡y rewrite trans (sym x⊔y≡z) (x⊔y≡y) = y≤z'
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NatMaxSemilattice : Semilattice ℕ
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NatMaxSemilattice = record
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{ _≼_ = _≤_
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; _⊔_ = _⊔_
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; isSemilattice = record
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{ isPreorder = Preorder.isPreorder NatPreorder
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; ⊔-assoc = ⊔-assoc
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; ⊔-comm = ⊔-comm
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; ⊔-idemp = ⊔-idem
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; ⊔-bound = λ x y z x⊔y≡z → (max-bound₁ x⊔y≡z , max-bound₂ x⊔y≡z)
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; ⊔-least = max-least
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}
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}
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private
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min-bound₁ : {x y z : ℕ} → x ⊓ y ≡ z → z ≤ x
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min-bound₁ {x} {y} {z} x⊓y≡z rewrite sym x⊓y≡z = m≤n⇒m⊓o≤n y (≤-refl)
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min-bound₂ : {x y z : ℕ} → x ⊓ y ≡ z → z ≤ y
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min-bound₂ {x} {y} {z} x⊓y≡z rewrite sym x⊓y≡z rewrite ⊓-comm x y = m≤n⇒m⊓o≤n x (≤-refl)
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min-greatest : (x y z : ℕ) → x ⊓ y ≡ z → ∀ (z' : ℕ) → (z' ≤ x × z' ≤ y) → z' ≤ z
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min-greatest x y z x⊓y≡z z' (z'≤x , z'≤y) with (⊓-sel x y)
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... | inj₁ x⊓y≡x rewrite trans (sym x⊓y≡z) (x⊓y≡x) = z'≤x
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... | inj₂ x⊓y≡y rewrite trans (sym x⊓y≡z) (x⊓y≡y) = z'≤y
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NatMinSemilattice : Semilattice ℕ
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NatMinSemilattice = record
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{ _≼_ = _≥_
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; _⊔_ = _⊓_
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; isSemilattice = record
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{ isPreorder = isPreorderFlip (Preorder.isPreorder NatPreorder)
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; ⊔-assoc = ⊓-assoc
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; ⊔-comm = ⊓-comm
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; ⊔-idemp = ⊓-idem
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; ⊔-bound = λ x y z x⊓y≡z → (min-bound₁ x⊓y≡z , min-bound₂ x⊓y≡z)
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; ⊔-least = min-greatest
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}
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}
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private
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minmax-absorb : {x y : ℕ} → x ⊓ (x ⊔ y) ≡ x
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minmax-absorb {x} {y} = ≤-antisym x⊓x⊔y≤x (helper x⊓x≤x⊓x⊔y (⊓-idem x))
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where
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x⊓x⊔y≤x = min-bound₁ {x} {x ⊔ y} {x ⊓ (x ⊔ y)} refl
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x⊓x≤x⊓x⊔y = ⊓-mono-≤ {x} {x} ≤-refl (max-bound₁ {x} {y} {x ⊔ y} refl)
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-- >:(
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helper : x ⊓ x ≤ x ⊓ (x ⊔ y) → x ⊓ x ≡ x → x ≤ x ⊓ (x ⊔ y)
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helper x⊓x≤x⊓x⊔y x⊓x≡x rewrite x⊓x≡x = x⊓x≤x⊓x⊔y
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maxmin-absorb : {x y : ℕ} → x ⊔ (x ⊓ y) ≡ x
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maxmin-absorb {x} {y} = ≤-antisym (helper x⊔x⊓y≤x⊔x (⊔-idem x)) x≤x⊔x⊓y
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where
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x≤x⊔x⊓y = max-bound₁ {x} {x ⊓ y} {x ⊔ (x ⊓ y)} refl
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x⊔x⊓y≤x⊔x = ⊔-mono-≤ {x} {x} ≤-refl (min-bound₁ {x} {y} {x ⊓ y} refl)
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-- >:(
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helper : x ⊔ (x ⊓ y) ≤ x ⊔ x → x ⊔ x ≡ x → x ⊔ (x ⊓ y) ≤ x
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helper x⊔x⊓y≤x⊔x x⊔x≡x rewrite x⊔x≡x = x⊔x⊓y≤x⊔x
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NatLattice : Lattice ℕ
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NatLattice = record
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{ _≼_ = _≤_
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; _⊔_ = _⊔_
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; _⊓_ = _⊓_
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; isLattice = record
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{ joinSemilattice = Semilattice.isSemilattice NatMaxSemilattice
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; meetSemilattice = Semilattice.isSemilattice NatMinSemilattice
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; absorb-⊔-⊓ = λ x y → maxmin-absorb {x} {y}
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; absorb-⊓-⊔ = λ x y → minmax-absorb {x} {y}
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}
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}
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ProdSemilattice : {a : Level} → {A B : Set a} → {{ Semilattice A }} → {{ Semilattice B }} → Semilattice (A × B)
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ProdSemilattice {a} {A} {B} {{slA}} {{slB}} = record
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{ _≼_ = λ (a₁ , b₁) (a₂ , b₂) → Semilattice._≼_ slA a₁ a₂ × Semilattice._≼_ slB b₁ b₂
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; _⊔_ = λ (a₁ , b₁) (a₂ , b₂) → (Semilattice._⊔_ slA a₁ a₂ , Semilattice._⊔_ slB b₁ b₂)
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; isSemilattice = record
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{
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}
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}
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