Day 9

day09/Commons.hs

@@ -0,0 +1,26 @@
+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)