Haskell Day 2016 演習

2-1_hostname.hs

#!/usr/bin/env stack
-- stack --install-ghc runghc --package turtle
import Turtle

main = hostname >>= echo

2-2_modified.hs

#!/usr/bin/env stack
-- stack --install-ghc runghc --package turtle
import Turtle

main = do
  as <- arguments
  d <- datefile $ fromText $ head as
  echo $ repr d

2-3_modified-multi.hs

#!/usr/bin/env stack
-- stack --install-ghc runghc --package turtle
import Turtle

main = do
  as <- arguments
  mapM echoModified as

echoModified :: MonadIO m => Text -> m ()
echoModified filename = do
  d <- datefile $ fromText $ filename
  echo $ repr d

2-4_io.hs

#!/usr/bin/env stack
-- stack --install-ghc runghc --package turtle
import Turtle

main = do
  x <- nestedIO
  x

nestedIO :: IO (IO ())
nestedIO = do
  putStr "Hello, "
  return (putStrLn "I/0!")