24 lines
672 B
Haskell
24 lines
672 B
Haskell
database :: [(Integer, String)]
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database = [(1, "Julie"),
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(2, "Chris"),
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(3, "Alonzo"),
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(4, "Melman")]
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greetUser :: Integer -> Maybe String
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greetUser record = fmap ("Hello, " ++) ((lookup record database) >>= makeUsername)
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removeSpaces :: String -> Maybe String
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removeSpaces string =
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case (filter (/= ' ') string) of
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"" -> Nothing
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result -> Just result
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validateLength :: String -> Maybe String
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validateLength string =
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case (length string > 25) of
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True -> Nothing
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False -> Just string
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makeUsername :: String -> Maybe String
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makeUsername string = removeSpaces string >>= validateLength |