{-# LANGUAGE RebindableSyntax #-}
{-# LANGUAGE NPlusKPatterns #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeFamilies #-}

module Main where
        {
        import qualified Prelude;
        import Prelude(String,undefined,Maybe(..),IO,putStrLn,
                Integer,(++),Rational, (==), (>=) );

        debugFunc :: String -> IO a -> IO a;
        debugFunc s ioa = (putStrLn ("++ " ++ s)) Prelude.>>
                (ioa Prelude.>>= (\a ->
                        (putStrLn ("-- " ++ s)) Prelude.>> (Prelude.return a)
                ));

        infixl 1 >>=;
        infixl 1 >>;

        returnIO :: a -> IO a;
        returnIO = Prelude.return;

        class HasReturn a where
                {
                return :: a;
                };

        class HasBind a where
                {
                (>>=) :: a;
                };

        class HasSeq a where
                {
                (>>) :: a;
                };

        class HasFail a where
                {
                fail :: a;
                };

        instance HasReturn (a -> IO a) where
                {
                return a = debugFunc "return" (Prelude.return a);
                };

        instance HasBind (IO a -> (a -> IO b) -> IO b) where
                {
                (>>=) ma amb = debugFunc ">>=" ((Prelude.>>=) ma amb);
                };

        instance HasSeq (IO a -> IO b -> IO b) where
                {
                (>>) ma mb = debugFunc ">>" ((Prelude.>>) ma mb);
                };

        instance HasFail (String -> IO a) where
                {
                fail s = debugFunc "fail" (Prelude.return undefined);
        --      fail s = debugFunc "fail" (Prelude.fail s);
                };

        class HasFromInteger a where
                {
                fromInteger :: a;
                };

        instance HasFromInteger (Integer -> Integer) where
                {
                fromInteger a = a Prelude.+ a Prelude.+ a Prelude.+ a Prelude.+ a; -- five times
                };

        class HasFromRational a where
                {
                fromRational :: a;
                };

        instance HasFromRational (Rational -> Rational) where
                {
                fromRational a = a Prelude.+ a Prelude.+ a; -- three times
                };

        class HasNegate a where
                {
                negate :: a;
                };

        instance (b ~ (a -> a)) => HasNegate b where
                {
                negate a = a; -- don't actually negate
                };

        class HasMinus a where
                {
                (-) :: a;
                };

        instance (b ~ (a -> a -> a)) => HasMinus b where
                {
                (-) x y = y; -- changed function
                };

        test_do :: forall a b. IO a -> IO (Maybe b) -> IO b;
        test_do f g = do
                {
                f;                      -- >>
                Just (b::b) <- g;       -- >>= (and fail if g returns Nothing)
                return b;               -- return
                };

        test_fromInteger :: Integer;
        test_fromInteger = 27;

        test_fromRational :: Rational;
        test_fromRational = 31.5;

        test_negate :: Integer -> Integer;
        test_negate a = - a;

        test_fromInteger_pattern :: Integer -> String;
        test_fromInteger_pattern a@1 = "1=" ++ (Prelude.show a);
        test_fromInteger_pattern a@(-2) = "(-2)=" ++ (Prelude.show a);
        test_fromInteger_pattern (a + 7) = "(a + 7)=" ++ Prelude.show a;

        test_fromRational_pattern :: Rational -> String;
        test_fromRational_pattern a@0.5 = "0.5=" ++ (Prelude.show a);
        test_fromRational_pattern a@(-0.7) = "(-0.7)=" ++ (Prelude.show a);
        test_fromRational_pattern a = "_=" ++ (Prelude.show a);


        doTest :: String -> IO a -> IO ();
        doTest s ioa =
                (putStrLn ("start test " ++ s))
                        Prelude.>>
                ioa
                        Prelude.>>
                (putStrLn ("end test " ++ s));

        main :: IO ();
        main =
                (doTest "test_do failure"
                        (test_do (Prelude.return ()) (Prelude.return Nothing))
                )
                        Prelude.>>
                (doTest "test_do success"
                        (test_do (Prelude.return ()) (Prelude.return (Just ())))
                )
                        Prelude.>>
                (doTest "test_fromInteger"
                        (putStrLn (Prelude.show test_fromInteger))
                )
                        Prelude.>>
                (doTest "test_fromRational"
                        (putStrLn (Prelude.show test_fromRational))
                )
                        Prelude.>>
                (doTest "test_negate"
                        (putStrLn (Prelude.show (test_negate 3)))
                )
                        Prelude.>>
                (doTest "test_fromInteger_pattern 1"
                        (putStrLn (test_fromInteger_pattern 1))
                )
                        Prelude.>>
                (doTest "test_fromInteger_pattern (-2)"
                        (putStrLn (test_fromInteger_pattern (-(2::Integer)::Integer)))
                )
                        Prelude.>>
                (doTest "test_fromInteger_pattern 9"
                        (putStrLn (test_fromInteger_pattern 9))
                )
                        Prelude.>>
                (doTest "test_fromRational_pattern 0.5"
                        (putStrLn (test_fromRational_pattern 0.5))
                )
                        Prelude.>>
                (doTest "test_fromRational_pattern (-0.7)"
                        (putStrLn (test_fromRational_pattern (-(0.7::Rational)::Rational)))
                )
                        Prelude.>>
                (doTest "test_fromRational_pattern 1.7"
                        (putStrLn (test_fromRational_pattern 1.7))
                );
        }