Demonstrate how to use Stack for scripts (+email address validation)

ParseEmail.hs

{- stack script
 --resolver lts-16.0
 --package bytestring
 --package email-validate
 --ghc-options -Wall
 --install-ghc
 --compile
-}

-- * Command Line Usage:
--
-- >>> echo "invalid\[email protected]" | stack ParseEmail.hs
-- - invalid (at sign > @: not enough input)
-- + [email protected]

{-# LANGUAGE OverloadedStrings #-}

import qualified Data.ByteString.Char8 as BC
import           System.IO             (stderr)
import           Text.Email.Validate   (validate)

main :: IO ()
main = mapM_ validateAndShow =<< BC.lines <$> BC.getContents

validateAndShow :: BC.ByteString -> IO ()
validateAndShow s =
  case validate s of
    Left e  -> BC.hPutStrLn stderr ("- " <> s <> " (" <> BC.pack e <> ")")
    Right _ -> BC.putStrLn ("+ " <> s)