Add a Lattice instance for natural numbers.

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>
This commit is contained in:
Danila Fedorin 2023-07-14 18:18:17 -07:00
parent c6dddb177e
commit bac68b95f1

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@ -154,6 +154,27 @@ private module NatInstances where
} }
} }
private
minmax-absorb : {x y : } x (x y) x
minmax-absorb {x} {y} = ≤-antisym x⊓x⊔y≤x (helper x⊓x≤x⊓x⊔y (⊓-idem x))
where
x⊓x⊔y≤x = min-bound₁ {x} {x y} {x (x y)} refl
x⊓x≤x⊓x⊔y = ⊓-mono-≤ {x} {x} ≤-refl (max-bound₁ {x} {y} {x y} refl)
-- >:(
helper : x x x (x y) x x x x x (x y)
helper x⊓x≤x⊓x⊔y x⊓x≡x rewrite x⊓x≡x = x⊓x≤x⊓x⊔y
maxmin-absorb : {x y : } x (x y) x
maxmin-absorb {x} {y} = ≤-antisym (helper x⊔x⊓y≤x⊔x (⊔-idem x)) x≤x⊔x⊓y
where
x≤x⊔x⊓y = max-bound₁ {x} {x y} {x (x y)} refl
x⊔x⊓y≤x⊔x = ⊔-mono-≤ {x} {x} ≤-refl (min-bound₁ {x} {y} {x y} refl)
-- >:(
helper : x (x y) x x x x x x (x y) x
helper x⊔x⊓y≤x⊔x x⊔x≡x rewrite x⊔x≡x = x⊔x⊓y≤x⊔x
NatLattice : Lattice NatLattice : Lattice
NatLattice = record NatLattice = record
{ _≼_ = _≤_ { _≼_ = _≤_
@ -162,5 +183,7 @@ private module NatInstances where
; isLattice = record ; isLattice = record
{ joinSemilattice = Semilattice.isSemilattice NatMaxSemilattice { joinSemilattice = Semilattice.isSemilattice NatMaxSemilattice
; meetSemilattice = Semilattice.isSemilattice NatMinSemilattice ; meetSemilattice = Semilattice.isSemilattice NatMinSemilattice
; absorb-⊔-⊓ = λ x y maxmin-absorb {x} {y}
; absorb-⊓-⊔ = λ x y minmax-absorb {x} {y}
} }
} }