D1 Haskell: make cost calculation more readable

2019/1/day1.hs

@@ -5,13 +5,16 @@ main :: IO ()
 main = do
   content <- getContents
   let input = map read (lines content)
-  printf "Part 1: %d\n" (fuel input)
-  printf "Part 2: %d\n" (fuelrec input)
+  printf "Part 1: %d\n" (part1 input)
+  printf "Part 2: %d\n" (part2 input)
 
-fuel :: [Integer] -> Integer
-fuel xs = sum (map (subtract 2 . (`div` 3)) xs)
+part1 :: [Integer] -> Integer
+part1 xs = sum (map cost xs)
 
-fuelrec :: [Integer] -> Integer
-fuelrec xs = sum (map f xs) - sum xs where
-    f x | x > 0 = x + f ((subtract 2 . (`div` 3)) x)
+part2 :: [Integer] -> Integer
+part2 xs = sum (map f xs) - sum xs where
+    f x | x > 0 = x + f (cost x)
         | otherwise = 0
+
+cost :: Integer -> Integer
+cost x = div x 3 - 2