Sha256: 26a2030bfd2e04df2c2bdd28cf85e83aca560a6357a15f4daac8920184a412d3
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Versions: 62
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Contents
module Series (Error(..), largestProduct) where
import Control.Monad ((>=>))
import Data.Char (digitToInt, isDigit)
import Data.List (tails)
import Data.Maybe (mapMaybe)
import Safe (maximumMay)
import Safe.Exact (takeExactMay)
data Error = InvalidSpan | InvalidDigit Char deriving (Show, Eq)
rightOr :: a -> Maybe b -> Either a b
rightOr a Nothing = Left a
rightOr _ (Just x) = Right x
largestProduct :: (Integral a, Num b, Ord b) => a -> String -> Either Error b
largestProduct n = traverse charToNum >=> rightOr InvalidSpan . maximumMay . products
where
products = mapMaybe (fmap product . takeExactMay (fromIntegral n)) . tails
charToNum x
| isDigit x = Right . fromIntegral . digitToInt $ x
| otherwise = Left (InvalidDigit x)
Version data entries
62 entries across 62 versions & 1 rubygems