From a442f232e93ac25a246f2a17f1a26ea912bf74f9 Mon Sep 17 00:00:00 2001
From: yui-knk <spiketeika@gmail.com>
Date: Sun, 3 Aug 2014 12:52:29 +0900
Subject: [PATCH] Refactor #flatten_merge

Not to unnecessary recursive search.
---
 mrblib/mrb_set.rb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mrblib/mrb_set.rb b/mrblib/mrb_set.rb
index b1e5ca7f2..2b0d751c6 100644
--- a/mrblib/mrb_set.rb
+++ b/mrblib/mrb_set.rb
@@ -83,19 +83,19 @@ class Set
 #  end
 #
   def flatten_merge(set, seen = Set.new)
+    seen.add(set.object_id)
     set.each { |e|
       if e.is_a?(Set)
         if seen.include?(e_id = e.object_id)
           raise ArgumentError, "tried to flatten recursive Set"
         end
 
-        seen.add(e_id)
         flatten_merge(e, seen)
-        seen.delete(e_id)
       else
         add(e)
       end
     }
+    seen.delete(set.object_id)
 
     self
   end