Þarf nýjasta committið af qualified-do branchinhu hjá tweag, https://gitlab.haskell.com/tweag/ghc/
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QualifiedDo @ RFP 2020-06-25
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{-# LANGUAGE DataKinds #-} | |
{-# LANGUAGE KindSignatures #-} | |
{-# LANGUAGE TypeFamilies #-} | |
module M where | |
import GHC.TypeLits | |
data Merki = Leyndarmál | Opinbert | |
newtype LIO (l :: Merki) a = LIO {unLIO :: IO a} | |
runLIO :: LIO Opinbert a -> IO a | |
runLIO = unLIO | |
merkja :: a -> LIO m a | |
merkja = LIO . return | |
type family Hámark (a :: Merki) (b :: Merki) :: Merki where | |
Hámark Leyndarmál Opinbert = Leyndarmál | |
Hámark Opinbert Leyndarmál = Leyndarmál | |
Hámark m m = m | |
prenta :: Show a => a -> LIO Opinbert () | |
prenta = LIO . print | |
dulrita :: String -> LIO Leyndarmál () | |
dulrita = LIO . putStrLn . flip replicate '*' . length | |
takaVið :: LIO Leyndarmál String | |
takaVið = LIO (putStr "Lykilorð: " Prelude.>>= getLine) | |
(>>) :: LIO m1 a -> LIO m2 b -> LIO (Hámark m1 m2) b | |
a >> b = LIO (unLIO a Prelude.>> (unLIO b)) | |
(>>=) :: LIO m1 a -> (a -> LIO m2 b) -> LIO (Hámark m1 m2) b | |
a >>= b = LIO (unLIO a Prelude.>>= (unLIO . b)) |
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{-# LANGUAGE QualifiedDo #-} | |
{-# LANGUAGE DataKinds #-} | |
{-# LANGUAGE KindSignatures #-} | |
{-# LANGUAGE TypeFamilies #-} | |
module Main where | |
import qualified M as M | |
import M | |
main :: Prelude.IO () | |
main = M.runLIO $ M.do lykilorð <- takaVið | |
dulrita lykilorð | |
prenta lykilorð | |
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