do.hs

newtype TEST a = TEST { runTEST :: Int -> Double -> Either String (a, String, Double) }

instance Monad TEST where
  m >>= f = TEST $ \i db0 -> do
    (a,ch,db1) <- runTEST m i db0
    (a',ch',db2) <- runTEST (f a) rd db1
    return (a',ch ++ ch',db2)

instance Monad TEST where
  m >>= f = TEST $ \i db0 ->
    runTEST m i db0 >>= \(a,ch,db1) ->
    runTEST (f a) rd db1 >>= \(a',ch',db2) ->
    return (a',ch ++ ch',db2)