Re: [Haskell-cafe] "Casting" newtype to base type?

2 Jul 2013


      On Tue, Jul 02, 2013 at 03:03:08PM +0200, Vlatko Basic wrote:
...
Is there a nicer way to extract the 'IO String' from 'IOS',
without 'case' or without pattern matching the whole 'P'?
newtype IOS = IOS (IO String)
data P = P {
  getA :: String,
  getB :: String,
  getC :: IOS
  } deriving (Show, Eq)
getC_IO :: P -> IO String
getC_IO p =
  case getC p of
    IOS a -> a
getC_IO (P _ _ (IOS a)) = a
How about

    unIOS :: IOS -> IO String
    unIOS (IOS a) = a

    getC_IO :: P -> IO String
    getC_IO = unIOS . getC

Tom

Re: [Haskell-cafe] "Casting" newtype to base type?

Tom Ellis