21 lines
611 B
Haskell
21 lines
611 B
Haskell
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 = do
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account1 <- deposit 100 account
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account2 <- withdraw 200 account1
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account3 <- deposit 100 account2
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account4 <- withdraw 300 account3
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account5 <- deposit 1000 account4
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Just 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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