agda-spa/Map.agda

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open import Relation.Binary.PropositionalEquality as Eq using (_≡_; refl; sym; cong)
open import Relation.Binary.Definitions using (Decidable)
open import Relation.Binary.Core using (Rel)
open import Relation.Nullary using (Dec; yes; no)
open import Agda.Primitive using (Level; _⊔_)
module Map {a b : Level} (A : Set a) (B : Set b)
(≡-dec-A : Decidable (_≡_ {a} {A}))
where
open import Relation.Nullary using (¬_)
open import Data.Nat using ()
open import Data.String using (String; _++_)
open import Data.List using (List; []; _∷_)
open import Data.List.Membership.Propositional using ()
open import Data.List.Relation.Unary.All using (All; _∷_)
open import Data.List.Relation.Unary.Any using (Any; here; there) -- TODO: re-export these with nicer names from map
open import Data.Product using (_×_; _,_; Σ; proj₁ ; proj₂)
open import Data.Unit using ()
open import Data.Empty using ()
Map : Set (a b)
Map = List (A × B)
record ' : Set (a b) where
Unique : List (A × B) Set (a b)
Unique [] = '
Unique ((k , _) xs) = All (λ (k' , _) ¬ k k') xs × Unique xs
_∈_ : (A × B) Map Set (a b)
_∈_ p m = Data.List.Membership.Propositional._∈_ p m
subset : (_≈_ : B B Set b) Map Map Set (a b)
subset _≈_ m₁ m₂ = (k : A) (v : B) (k , v) m₁ Σ B (λ v' v v' × ((k , v') m₂))
lift : (_≈_ : B B Set b) Map Map Set (a b)
lift _≈_ m₁ m₂ = (m₁ m₂) × (m₂ m₁)
where
_⊆_ : Map Map Set (a b)
_⊆_ = subset _≈_
foldr : {c} {C : Set c} (A B C C) -> C -> Map -> C
foldr f b [] = b
foldr f b ((k , v) xs) = f k v (foldr f b xs)
insert : (B B B) A B Map Map
insert f k v [] = (k , v) []
insert f k v (x@(k' , v') xs) with ≡-dec-A k k'
... | yes _ = (k , f v v') xs
... | no _ = x insert f k v xs
merge : (B B B) Map Map Map
merge f m₁ m₂ = foldr (insert f) m₂ m₁
Map-functional : (k : A) (v v' : B) (xs : List (A × B)) Unique ((k , v) xs) Data.List.Membership.Propositional._∈_ (k , v') ((k , v) xs) v v'
Map-functional k v v' _ _ (here k,v'≡k,v) = sym (cong proj₂ k,v'≡k,v)
Map-functional k v v' xs (k≢ , _) (there k,v'∈xs) = absurd (unique-not-in xs v' (k≢ , k,v'∈xs))
where
absurd : {a} {A : Set a} A
absurd ()
unique-not-in : (xs : List (A × B)) (v' : B) ¬ (All (λ (k' , _) ¬ k k') xs × (k , v') xs)
unique-not-in ((k' , _) xs) v' (k≢k' _ , here k',≡x) = k≢k' (cong proj₁ k',≡x)
unique-not-in (_ xs) v' (_ rest , there k,v'∈xs) = unique-not-in xs v' (rest , k,v'∈xs)