module Commons where

import GHC.IO.Handle (isEOF)
import Data.List.Utils (split)


type History = [Int]


parse :: IO [History]
parse = do done <- isEOF
           if done
              then return []
              else do line <- getLine
                      let history = map read $ split " " line
                      otherHistories <- parse
                      return $ history: otherHistories


getDifferences :: History -> History
getDifferences [h] = []
getDifferences (h1: h2: t) = h1 - h2: getDifferences (h2: t)

getNextValue :: History -> Int
getNextValue (0: 0: _) = 0
getNextValue (h: t) = h + (getNextValue . getDifferences) (h: t)