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clean up a bit.

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Mahler, Thomas 2020-10-26 13:44:10 +01:00
parent 96674c2a87
commit e6fe297323
1 changed files with 11 additions and 12 deletions
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23
src/Luhn.hs
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@ -42,26 +42,25 @@ use it to validate the following numbers:
divisibleBy10 :: Int -> Bool
divisibleBy10 = (0 ==) . (`mod` 10)
sumDigits :: [Int] -> Int
sumDigits = sum . map (uncurry (+) . (`divMod` 10)) -- map (uncurry (+) . (`divMod` 10)) [6,2,7,16,9,6,7,4,9,18,4] -> [6,2,7,7,9,6,7,4,9,9,4]
sumUpDigits :: [Int] -> Int
sumUpDigits = sum . map (uncurry (+) . (`divMod` 10)) -- map (uncurry (+) . (`divMod` 10)) [6,2,7,16,9,6,7,4,9,18,4] -> [6,2,7,7,9,6,7,4,9,9,4]
double2nd :: [Int] -> [Int]
double2nd = zipWith (*) (cycle [1,2]) -- zipWith (*) [6,1,7,8,9,3,7,2,9,9,4] [1,2,1,2,1,2,1,2,1,2,1] -> [6,2,7,16,9,6,7,4,9,18,4]
doubleEach2nd :: [Int] -> [Int]
doubleEach2nd = zipWith (*) (cycle [1,2]) -- zipWith (*) [6,1,7,8,9,3,7,2,9,9,4] [1,2,1,2,1,2,1,2,1,2,1] -> [6,2,7,16,9,6,7,4,9,18,4]
toDigits :: Natural -> [Int]
toDigits = map digitToInt . show -- toDigits 49927398716 -> [4,9,9,2,7,3,9,8,7,1,6]
splitIntoDigits :: Natural -> [Int]
splitIntoDigits = reverse . map digitToInt . show -- toDigits 49927398716 -> [4,9,9,2,7,3,9,8,7,1,6]
luhn1 :: Natural -> Bool
luhn1 = divisibleBy10 . sumDigits . double2nd . reverse . toDigits
luhn1 = divisibleBy10 . sumUpDigits . doubleEach2nd . splitIntoDigits
luhn2 :: Natural -> Bool
luhn2 n = divisibleBy10 (sumDigits (double2nd (reverse (toDigits n))))
luhn2 n = divisibleBy10 (sumUpDigits (doubleEach2nd (splitIntoDigits n)))
luhn3 :: Natural -> Bool
luhn3 = toDigits >>>
reverse >>>
double2nd >>>
sumDigits >>>
luhn3 = splitIntoDigits >>>
doubleEach2nd >>>
sumUpDigits >>>
divisibleBy10
luhn4 :: Natural -> Bool