https://git.ruby-lang.org/ruby.git/commit/?id=4ce28b58cb

From 4ce28b58cbf3f3b5ab0bcd3fa4479d4f6d427158 Mon Sep 17 00:00:00 2001
From: Oleg Zubchenko <RedGreenBlueDiamond@g...>
Date: Sat, 3 Nov 2018 15:27:10 +0300
Subject: speed up set intersect


diff --git a/lib/set.rb b/lib/set.rb
index 5a96c81..e7d1be4 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -464,7 +464,15 @@ class Set https://github.com/ruby/ruby/blob/trunk/lib/set.rb#L464
   #     Set['a', 'b', 'z'] & ['a', 'b', 'c']    #=> #<Set: {"a", "b"}>
   def &(enum)
     n = self.class.new
-    do_with_enum(enum) { |o| n.add(o) if include?(o) }
+    if enum.is_a?(Set)
+      if enum.size > size
+        each { |o| n.add(o) if enum.include?(o) }
+      else
+        enum.each { |o| n.add(o) if include?(o) }
+      end
+    else
+      do_with_enum(enum) { |o| n.add(o) if include?(o) }
+    end
     n
   end
   alias intersection &
-- 
cgit v0.10.2


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