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--- maybe [2014/09/15 20:14]
nikolaj
+++ maybe [2014/09/15 20:19]
nikolaj
@@ Line 4: / Line 4: @@
 data  Maybe a  =  Nothing | Just a
   deriving (Eq, Ord)
-instance  Functor Maybe  where
-    fmap _ Nothing       = Nothing
-    fmap f (Just a)      = Just (f a)
 instance  Monad Maybe  where
     (Just x) >>= k      = k x
     Nothing  >>= _      = Nothing
-    (Just _) >>  k      = k
-    Nothing  >>  _      = Nothing
     return              = Just
     fail _              = Nothing
+-- utility
+   (Just _) >>  k      = k
+   Nothing  >>  _      = Nothing
+  instance  Functor Maybe  where
+    fmap _ Nothing       = Nothing
+    fmap f (Just a)      = Just (f a)
 </code>