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--- maybe [2014/09/15 20:17]
nikolaj
+++ maybe [2014/09/15 20:19]
nikolaj
@@ Line 6: / Line 6: @@
 instance  Monad Maybe  where
-    return x  =  Just x
     (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
+  instance  Functor Maybe  where
---  fmap _ Nothing       = Nothing
+    fmap _ Nothing       = Nothing
---  fmap f (Just a)      = Just (f a)
+    fmap f (Just a)      = Just (f a)
 </code>