21 lines
536 B
Haskell
21 lines
536 B
Haskell
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deposit :: (Num a) => a -> a -> Maybe a
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deposit value account = Just (account + value)
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withdraw :: (Num a,Ord a) => a -> a -> Maybe a
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withdraw value account = if (account < value)
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then Nothing
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else Just (account - value)
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eligible :: (Num a, Ord a) => a -> Maybe Bool
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eligible account =
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deposit 100 account >>=
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withdraw 200 >>=
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deposit 100 >>=
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withdraw 300 >>=
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deposit 1000 >>
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return True
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main = do
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print $ eligible 300 -- Just True
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print $ eligible 299 -- Nothing
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