diff --git a/2019/day10/day10.hs b/2019/day10/day10.hs
index 5e986b5..5bcf861 100644
--- a/2019/day10/day10.hs
+++ b/2019/day10/day10.hs
@@ -8,15 +8,13 @@ data Asteroid =
   deriving (Show)
 
 instance Eq Asteroid where
-  Asteroid a b == Asteroid c d = phi' a b == phi' c d
+  Asteroid a b == Asteroid c d = phi a b == phi c d
 
 instance Ord Asteroid where
   Asteroid a b `compare` Asteroid c d = phi a b `compare` phi c d
-    where
-      phi x y = phi' (fromIntegral x) (fromIntegral y)
 
-phi' :: Int -> Int -> Double
-phi' xi yi
+phi :: Int -> Int -> Double
+phi xi yi
  | x >= 0 = atan2 x (-y)
  | otherwise = 2 * pi + atan2 (-x) y
     where x = fromIntegral xi