diff --git a/Utils.hs b/Utils.hs
index d62a525..4c36888 100644
--- a/Utils.hs
+++ b/Utils.hs
@@ -3,3 +3,13 @@ module Utils where
 
 symbolic = (`elem` symbolic_ops)
 symbolic_ops = "!@#$%^&*+./<=>?\\^|:-~"
+
+-- doing 'partition f xs = (filter f xs, filter (not . f) xs)' is too
+-- slow, cuz it would run same test twice on every paramter. I might
+-- be wrong tho
+partition :: (a -> Bool) -> [a] -> ([a], [a])
+partition _ [] = ([], [])
+partition f (x:xs)
+  | f x = (x:pass, fail)
+  | otherwise = (pass, x:fail)
+  where (pass, fail) = partition f xs