24 lines
648 B
Haskell
24 lines
648 B
Haskell
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module Pal where
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import Data.Char
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isPalindrome :: String -> Maybe Bool
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isPalindrome = isOwnReverseMaybe . rejectEmpty . normalize
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rejectEmpty :: String -> Maybe String
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rejectEmpty w = case w of
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[] -> Nothing
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_ -> Just w
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normalize :: String -> String
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normalize = allLowercase . filter notSpace . filter notPunctuation
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where notSpace = not . isSpace
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notPunctuation = not . isPunctuation
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isOwnReverseMaybe :: Maybe String -> Maybe Bool
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isOwnReverseMaybe = fmap isOwnReverse
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isOwnReverse :: String -> Bool
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isOwnReverse word = word == reverse word
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allLowercase :: String -> String
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allLowercase = map toLower
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