-- ghc -package lang TestException.hs -o TestException
module Main where
	{
	import IORef;
	import qualified Exception;

	getPureException :: a -> IO (Maybe Exception.Exception);
	getPureException a = (Exception.catch (seq a (return Nothing)) (return . Just));

	showIOS :: String -> IO String -> IO ();
	showIOS s ios = do
		{
		putStr (s ++ ":	");
		mpe <- getPureException ios;
		case mpe of
			{
			Just pe -> putStrLn ("pure exception ("++ (show pe) ++")");
			Nothing -> do
				{
				result <- Exception.catch (ios) (\_ -> return "");
				mrpe <- getPureException result;
				case mrpe of
					{
					Just pe -> putStrLn ("returned pure exception ("++ (show pe) ++")");
					Nothing -> do
						{
						Exception.catch (do
							{
							s <- ios;
							putStrLn ("value ("++ (show s) ++")");
							})
							(\e -> putStrLn ("IO exception (" ++ (show e) ++")"));
						};
					};
				};
			};
		};

	evaluate' :: a -> IO a;
	evaluate' a = a `seq` return a;

	main :: IO ();
	main = do
		{
		showIOS "return text"			(return "text");
		showIOS "fail text"				(fail "text");
		showIOS "error text"			(error "text");
		showIOS "undefined"				undefined;
		showIOS "seq undefined (return text)"	(seq undefined (return "text"));
		showIOS "seq undefined (return undefined)"	(seq undefined (return undefined));
		showIOS "return (seq undefined text)"	(return (seq undefined "text"));
		showIOS "evaluate undefined"	(Exception.evaluate undefined);
		showIOS "evaluate' undefined"	(evaluate' undefined);
		showIOS "return undefined"		(return undefined);
		};
	}