{-# OPTIONS --cubical-compatible --safe #-}
module Data.List.Relation.Binary.Pointwise.Base where
open import Data.Product.Base as Product using (_×_; _,_; <_,_>; ∃-syntax)
open import Data.List.Base using (List; []; _∷_)
open import Level using (Level; _⊔_)
open import Relation.Binary.Core using (REL; _⇒_)
open import Relation.Binary.Construct.Composition using (_;_)
private
variable
a b c ℓ : Level
A B : Set a
x y : A
xs ys : List A
R S : REL A B ℓ
infixr 5 _∷_
data Pointwise {A : Set a} {B : Set b} (R : REL A B ℓ)
: List A → List B → Set (a ⊔ b ⊔ ℓ) where
[] : Pointwise R [] []
_∷_ : (x∼y : R x y) (xs∼ys : Pointwise R xs ys) →
Pointwise R (x ∷ xs) (y ∷ ys)
head : Pointwise R (x ∷ xs) (y ∷ ys) → R x y
head (x∼y ∷ xs∼ys) = x∼y
tail : Pointwise R (x ∷ xs) (y ∷ ys) → Pointwise R xs ys
tail (x∼y ∷ xs∼ys) = xs∼ys
uncons : Pointwise R (x ∷ xs) (y ∷ ys) → R x y × Pointwise R xs ys
uncons = < head , tail >
rec : ∀ (P : ∀ {xs ys} → Pointwise R xs ys → Set c) →
(∀ {x y xs ys} {Rxsys : Pointwise R xs ys} →
(Rxy : R x y) → P Rxsys → P (Rxy ∷ Rxsys)) →
P [] →
∀ {xs ys} (Rxsys : Pointwise R xs ys) → P Rxsys
rec P c n [] = n
rec P c n (Rxy ∷ Rxsys) = c Rxy (rec P c n Rxsys)
map : R ⇒ S → Pointwise R ⇒ Pointwise S
map R⇒S [] = []
map R⇒S (Rxy ∷ Rxsys) = R⇒S Rxy ∷ map R⇒S Rxsys
unzip : Pointwise (R ; S) ⇒ (Pointwise R ; Pointwise S)
unzip [] = [] , [] , []
unzip ((y , r , s) ∷ xs∼ys) =
Product.map (y ∷_) (Product.map (r ∷_) (s ∷_)) (unzip xs∼ys)