Implement 2015's day 3 because I'm a doofus

3.hs

@@ -0,0 +1,29 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+import Data.List
+
+main = do
+    lines <- readFile "3.in"
+    putStrLn . show . solve . (!!0) . words $ lines
+    where
+        solve = length . Data.List.group . Data.List.sort . partB
+
+-- solves all lines, returns a string
+partA :: [Char] -> [(Int, Int)]
+partA = getPositions
+    where
+        getPositions = snd . foldl updatePosition ((0,0), [(0,0)]) . map coords
+        -- updatePosition :: b -> a -> b
+        updatePosition ((x, y), positions) (a, b) = ((x + a, y + b), (x + a, y + b):positions)
+        -- (right, up)
+        coords '>' = (1, 0)
+        coords '<' = (-1, 0)
+        coords 'v' = (0, -1)
+        coords '^' = (0, 1)
+        coords  _  = (0, 0)
+
+partB :: [Char] -> [(Int, Int)]
+partB l = id =<< [ partA . odds $ l, partA . odds . tail $ l]
+    where
+        odds [] = []
+        odds [x] = [x]
+        odds (x:y:r) = x:(odds r)

Makefile

@@ -1,3 +1,4 @@
 target:
 	ghc 1.hs
 	ghc 2.hs
+	ghc 3.hs