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module Examples where
open import Data.Maybe using (just ; nothing)
open import Data.Nat using (ℕ ; zero ; suc ; _+_ ; ⌈_/2⌉)
open import Data.Nat.Properties using (cancel-+-left ; ≤-decTotalOrder)
import Algebra.Structures
open import Data.List using (List ; length) renaming ([] to []L ; _∷_ to _∷L_)
open import Data.Vec using (Vec ; [] ; _∷_ ; reverse ; _++_ ; tail ; take ; drop ; map)
open import Function using (id)
import Relation.Binary
open import Relation.Binary.PropositionalEquality as P using (_≡_)
open import Structures using (Shaped)
import GetTypes
import FreeTheorems
import BFF
open GetTypes.PartialVecVec using (Get)
open FreeTheorems.PartialVecVec using (assume-get)
open BFF.PartialVecBFF using (bff)
ℕ-decSetoid = Relation.Binary.DecTotalOrder.Eq.decSetoid ≤-decTotalOrder
reverse' : Get
reverse' = assume-get id id reverse
double' : Get
double' = assume-get id g f
where g : ℕ → ℕ
g zero = zero
g (suc n) = suc (suc (g n))
f : {A : Set} {n : ℕ} → Vec A n → Vec A (g n)
f [] = []
f (x ∷ v) = x ∷ x ∷ f v
double'' : Get
double'' = assume-get id _ (λ v → v ++ v)
tail' : Get
tail' = assume-get suc id tail
tail-example : bff ℕ-decSetoid tail' 2 (8 ∷ 5 ∷ []) (3 ∷ 1 ∷ []) ≡ just (just 8 ∷ just 3 ∷ just 1 ∷ [])
tail-example = P.refl
take' : ℕ → Get
take' n = assume-get (_+_ n) _ (take n)
drop' : ℕ → Get
drop' n = assume-get (_+_ n) _ (drop n)
sieve' : Get
sieve' = assume-get id _ f
where f : {A : Set} {n : ℕ} → Vec A n → Vec A ⌈ n /2⌉
f [] = []
f (x ∷ []) = x ∷ []
f (x ∷ _ ∷ xs) = x ∷ f xs
sieve-example : bff ℕ-decSetoid sieve' 4 (0 ∷ 2 ∷ []) (1 ∷ 3 ∷ []) ≡ just (just 1 ∷ just 2 ∷ just 3 ∷ nothing ∷ [])
sieve-example = P.refl
intersperse-len : ℕ → ℕ
intersperse-len zero = zero
intersperse-len (suc zero) = suc zero
intersperse-len (suc (suc n)) = suc (suc (intersperse-len (suc n)))
intersperse : {A : Set} {n : ℕ} → A → Vec A n → Vec A (intersperse-len n)
intersperse s [] = []
intersperse s (x ∷ []) = x ∷ []
intersperse s (x ∷ y ∷ v) = x ∷ s ∷ intersperse s (y ∷ v)
intersperse' : Get
intersperse' = assume-get suc intersperse-len f
where f : {A : Set} {n : ℕ} → Vec A (suc n) → Vec A (intersperse-len n)
f (s ∷ v) = intersperse s v
intersperse-neg-example : bff ℕ-decSetoid intersperse' 3 (0 ∷ []) (1 ∷ 2 ∷ 3 ∷ 4 ∷ 5 ∷ []) ≡ nothing
intersperse-neg-example = P.refl
intersperse-pos-example : bff ℕ-decSetoid intersperse' 3 (0 ∷ []) (1 ∷ 2 ∷ 3 ∷ 2 ∷ 5 ∷ []) ≡ just (map just (2 ∷ 1 ∷ 3 ∷ 5 ∷ []))
intersperse-pos-example = P.refl
data PairVec (α : Set) (β : Set) : List α → Set where
[]P : PairVec α β []L
_,_∷P_ : (x : α) → β → {l : List α} → PairVec α β l → PairVec α β (x ∷L l)
PairVecFirstShaped : (α : Set) → Shaped (List α) (PairVec α)
PairVecFirstShaped α = record
{ arity = length
; content = content
; fill = fill
; isShaped = record
{ content-fill = content-fill
; fill-content = fill-content
} }
where content : {β : Set} {s : List α} → PairVec α β s → Vec β (length s)
content []P = []
content (a , b ∷P p) = b ∷ content p
fill : {β : Set} → (s : List α) → Vec β (length s) → PairVec α β s
fill []L v = []P
fill (a ∷L s) (b ∷ v) = a , b ∷P fill s v
content-fill : {β : Set} {s : List α} → (p : PairVec α β s) → fill s (content p) ≡ p
content-fill []P = P.refl
content-fill (a , b ∷P p) = P.cong (_,_∷P_ a b) (content-fill p)
fill-content : {β : Set} → (s : List α) → (v : Vec β (length s)) → content (fill s v) ≡ v
fill-content []L [] = P.refl
fill-content (a ∷L s) (b ∷ v) = P.cong (_∷_ b) (fill-content s v)
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