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26 lines
784 B
Haskell
26 lines
784 B
Haskell
module Week04.Maybe where
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import Text.Read (readMaybe)
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import Week04.Monad
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foo :: String -> String -> String -> Maybe Int
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foo x y z = case readMaybe x of
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Nothing -> Nothing
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Just k -> case readMaybe y of
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Nothing -> Nothing
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Just l -> case readMaybe z of
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Nothing -> Nothing
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Just m -> Just (k + l + m)
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bindMaybe :: Maybe a -> (a -> Maybe b) -> Maybe b
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bindMaybe Nothing _ = Nothing
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bindMaybe (Just x) f = f x
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foo' :: String -> String -> String -> Maybe Int
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foo' x y z = readMaybe x `bindMaybe` \k ->
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readMaybe y `bindMaybe` \l ->
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readMaybe z `bindMaybe` \m ->
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Just (k + l + m)
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foo'' :: String -> String -> String -> Maybe Int
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foo'' x y z = threeInts (readMaybe x) (readMaybe y) (readMaybe z)
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