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+definition module monad
+
+/*
+	Pieter Koopman, pieter@cs.ru.nl
+	Advanced Programming, week 4
+*/
+
+import StdMisc
+
+class Functor f where
+	fmap :: (a->b) (f a) -> (f b)
+	(<$>) infixl 4 :: (a->b) (f a) -> (f b) | Functor f
+ 	(<$>) f x :== fmap f x
+
+class Applicative f | Functor f where
+	pure :: a -> f a
+	(<*>) infixl 4 :: (f (a->b)) (f a) -> f b
+
+class Monad m | Applicative m where
+	bind :: (m a) (a->m b) -> m b
+	(>>=) infixl 1 :: (m a) (a->m b) -> m b | Monad m
+	(>>=) a f :== bind a f
+	(>>|) infixl 1 :: (m a)    (m b) -> m b | Monad m
+	(>>|) a b :== a >>= \_.b
+	rtrn :: a -> m a | Monad m
+	rtrn a :== pure a
+
+class fail m | Applicative m where
+	fail :: m a
+	guard :: Bool -> m a | fail m
+	guard b :== if b (pure undef) fail
+
+class OrMonad m where
+	(<|>) infixl 0 :: (m a) (m a) -> m a
+