Ticket #2209: Main_bug.hs

{-# OPTIONS -O2 #-}
{-# OPTIONS -fasm #-}
{-# LANGUAGE MagicHash #-}

import GHC.Word
import GHC.Exts

word64ToDouble :: Word64 -> Double
word64ToDouble w@(W64# x) = D# (unsafeCoerce# x)

doubleToWord64 :: Double -> Word64
doubleToWord64 d@(D# x) = W64# (unsafeCoerce# x)

main :: IO ()
main = do

  -- Bug 1
  let
      i :: Integer
      i = 17 + (2047 * (2 ^ 52))

      d :: Double
      d = word64ToDouble (fromInteger i)

  if (isNaN d)
         then putStrLn ("True")
         else putStrLn ("False: " ++ show d)

  -- Bug 2
  let
      d :: Double
      d = 2.0

      w :: Word64
      w = doubleToWord64 d

  putStrLn (show w)
  -- ought to be this
  let i :: Integer
      i = 1024 * (2 ^ 52)
  putStrLn ("expect: " ++ show i)