Smooth out slime splitting

There are probably possible errors from the use of cutPoly

src/Geometry/Polygon.hs

@@ -188,7 +188,7 @@ grahamEliminate (x : y : z : xs)
     | not $ isLHS x y z = grahamEliminate (x : z : xs)
 grahamEliminate xs = xs
 
--- this isn't the centroid of the polygon...
+-- not sure what definition of centroid is applicable here
 centroid :: (Num (f a),Functor f, Fractional a,Foldable t) => t (f a) -> f a
 centroid = L.fold $ (^/) <$> L.Fold (+) 0 id <*> L.genericLength
 
@@ -234,9 +234,15 @@ cutPolyR a b [] e x ls rs = case intersectSegLine x e a b of
     Nothing -> (reverse ls,reverse rs)
     Just p -> (reverse (p\:ls), reverse (p\:rs))
 
+polyInPoly :: Point2 -> [Point2] -> [Point2] -> [Point2]
+polyInPoly p ps = mapMaybe f
+  where
+    f q = intersectRayPoly p q ps
+
 infixr 5 \:
 (\:) :: Eq a => a -> [a] -> [a]
 (\:) x (y:ys) 
     | x /= y = x:y:ys
     | otherwise = y:ys 
 (\:) x [] = [x]
+