Cedev

{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DeriveGeneric #-} -- Only needed for the DSL example

import GHC.Generics

-- Data types that are constant and uninteresting
class Eq a => Const a

Cedev

main = do
    chars <- getLine
    let otherchars = do 
        a <- chars
        b <- chars
        [a] ++ [b]
    putStrLn otherchars

Cedev

{-# language DeriveFunctor #-}
{-# language FlexibleInstances #-}

import Data.Function

class Functor w => Comonad w where
  extract :: w a -> a
  duplicate :: w a -> w (w a)
  
kfix :: ComonadApply w => w (w a -> a) -> w a

Cedev

{-# Language GADTs #-}
{-# Language DataKinds #-}
{-# Language KindSignatures #-}
{-# Language ViewPatterns #-}
{-# Language RankNTypes #-}
{-# Language ScopedTypeVariables #-}


import Control.Applicative

Cedev

{-# LANGUAGE PolyKinds, DataKinds, GADTs, TypeOperators, ConstraintKinds, RankNTypes, MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, UndecidableInstances #-}

import Data.Proxy
import Data.Functor.Identity
import GHC.Exts (Constraint)

data HKList :: (k -> *) -> [k] -> * where
  Nil  :: HKList f '[]
  (:*) :: f x -> HKList f xs -> HKList f (x ': xs)