Day 01 - minor editing, contracting part 2.

src/Day01.hs

@@ -1,25 +1,21 @@
 module Day01 (main) where
 
-import Data.Set (empty, insert, member)
+import Data.IntSet (empty, insert, member)
 
-freqChangeList :: String -> [Int]
-freqChangeList = map (read . dropWhile (== '+')) . lines
+parseChanges :: String -> [Int]
+parseChanges = map (read . dropWhile (== '+')) . lines
 
-totalFrequency :: [Int] -> Int
-totalFrequency = foldr1 (+)
+part1 :: [Int] -> Int
+part1 = sum
 
-firstFreqTwice :: [Int] -> Int
-firstFreqTwice changeList =
-    let freqs = scanl1 (+) $ cycle changeList
-    in  dupl freqs empty
-    where dupl (f:fs) s =
-            if   member f s
-            then f
-            else dupl fs (insert f s)
+part2 :: [Int] -> Int
+part2 = dupl empty . scanl1 (+) . cycle
+    where dupl s (f:fs)
+            | member f s = f
+            | otherwise  = dupl (insert f s) fs
 
 main :: IO ()
 main = do
-    input <- readFile "input/01.txt"
-    let changeList = freqChangeList input
-    print $ totalFrequency changeList
-    print $ firstFreqTwice changeList
+    changes <- parseChanges <$> readFile "input/01.txt"
+    print $ part1 changes
+    print $ part2 changes