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dmatveev/gist:1922080

Created February 27, 2012 06:57
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A poor man's monad
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gistfile1.hs
(>>?) :: (Ord a, Num a) => Maybe a -> (a -> Maybe b) -> Maybe b
Nothing >>? _ = Nothing
Just v >>? f = if v > 0 then f v else Nothing
decr :: Int -> Maybe Int
decr a = Just (a - 1)
ex1 = (Just 1) >>? decr >>? decr >>? decr
ex2 = (Just 10) >>? decr >>? decr >>? decr
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