bsc-leon-vatthauer/thesis/agda/motivation.agda

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{-# OPTIONS --guardedness #-}
-- Take this example as motivation:
-- https://stackoverflow.com/questions/21808186/agda-reading-a-line-of-standard-input-as-a-string-instead-of-a-costring
open import Level
open import Agda.Builtin.Coinduction
module thesis.motivation where
module old-delay where
private
variable
a : Level
data _⊥ (A : Set a) : Set a where
now : A A
later : (A ) A
never : {A : Set a} A
never = later ( never)
module ReverseInput where
open import Data.Char
open import Data.Nat
open import Data.List using (List; []; _∷_)
open import Data.String
open import Data.Unit.Polymorphic
open import Codata.Musical.Costring
open import Codata.Musical.Colist using ([]; _∷_)
-- open import IO using (IO; seq; bind; return; Main; run; putStrLn)
open import IO.Primitive
open import IO.Primitive.Infinite using (getContents)
open import Agda.Builtin.IO using ()
open old-delay
-- IDEA: start in haskell, then motivate in agda and define delay type
-- next talk about bisimilarity.
-- idea for slide title: dlrowolleh.hs and dlrowolleh.agda
private
variable
a : Level
-- reverse : Costring → String ⊥
-- reverse = go []
-- where
-- go : List Char → Costring → String ⊥
-- go acc [] = now (fromList acc)
-- go acc (x ∷ xs) = later (♯ go (x ∷ acc) (♭ xs))
-- putStrLn⊥ : String ⊥ → IO {a}
-- putStrLn⊥ (now s) = putStrLn s
-- putStrLn⊥ (later s) = seq (♯ return tt) (♯ putStrLn⊥ (♭ s))
-- main : Main
-- main = run (bind (♯ {! getContents !}) {! !}) --(λ c → ♯ putStrLn⊥ (reverse c)))
-- NOTE: This is not very understandable... Better stick to the outdated syntax
module delay where
mutual
data _⊥ (A : Set) : Set where
now : A A
later : A ⊥' A
record _⊥' (A : Set) : Set where
coinductive
field
force : A
open _⊥'
mutual
never : {A : Set} A
never = later never'
never' : {A : Set} A ⊥'
force never' = never