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itarato/ch197e.hs

Created January 14, 2015 18:49
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Challenge 197 easy
Raw
ch197e.hs
validISBN x y
| x > 9 = validISBN (reduce (fromIntegral x)) (extra (fromIntegral x) y)
| otherwise = elevens (fromIntegral x) y
reduce x = round(x) `mod` (tens x)
lvl x = floor $ logBase 10 x
extra x y = y + ((round(x) `div` (tens x)) * ((lvl x) + 1))
tens x = round(10 ^^ (lvl x))
elevens x y = ((round(x) + y) `mod` 11) == 0
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