Tweak movement

src/Geometry/Vector.hs

@@ -72,11 +72,13 @@ normalizeV p = (1 / magV p) *.* p
 {- | Angle between two vectors.  Always positive.  -}
 angleVV :: Point2 -> Point2 -> Float
 {-# INLINE angleVV #-}
-angleVV a b = 
-    let ma = magV a
-        mb = magV b
-        d  = a `dotV` b
-    in  acos $ d / (ma * mb)
+angleVV a b 
+    | a == b = 0
+    | otherwise =
+        let ma = magV a
+            mb = magV b
+            d  = a `dotV` b
+        in  acos $ d / (ma * mb)
 {- | Safe version of 'angleVV' that returns 0 if either vector is null. -}
 safeAngleVV :: Point2 -> Point2 -> Float
 {-# INLINE safeAngleVV #-}