JustinSDK

import Unsafe.Coerce

y :: (a -> a) -> a
y = \f -> (\x -> f (unsafeCoerce x x))(\x -> f (unsafeCoerce x x))

-- Ref: [Y Combinator in Haskell](http://stackoverflow.com/questions/4273413/y-combinator-in-haskell)
-- a fibonacci example
main = putStrLn $ show $ y (\fact -> \n -> if n < 2 then 1 else n * fact (n - 1)) 5

phadej

-- Compile with
-- ghc -Wall -O -fforce-recomp -ddump-simpl -dsuppress-all poly.hs
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Poly (value, ualue, xalue) where

import Data.Proxy (Proxy (..))

kana-sama

{-# LANGUAGE RankNTypes, TypeInType, TypeApplications, OverloadedLabels,
  ScopedTypeVariables, TypeOperators, GADTs, FlexibleInstances, FlexibleContexts,
  TypeFamilies, UndecidableInstances #-}

import Data.Kind (Type)
import Data.Proxy (Proxy(..))
import GHC.Generics
import GHC.TypeLits (Symbol, KnownSymbol, symbolVal)
import Control.Lens
import Data.Generics.Product.Fields (field')