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shigemk2/applyMaybe.hs

Created September 2, 2015 12:04
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applyMaybe.hs
-- オレオレバインド(>>=)の実装
applyMaybe :: Maybe a -> (a -> Maybe b) -> Maybe b
applyMaybe Nothing f = Nothing
applyMaybe (Just x) f = f x
main = do
print $ Just 3 `applyMaybe` \ x -> Just (x+1)
print $ Just "smile" `applyMaybe` \ x -> Just (x ++ " :)")
print $ Nothing `applyMaybe` \ x -> Just (x+1)
print $ Nothing `applyMaybe` \ x -> Just (x ++ " :)")
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