From 1cca2e29eecd72652be3ac09aedc581f5e31456d Mon Sep 17 00:00:00 2001
From: marcandre <marcandre@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Tue, 20 Oct 2015 03:18:14 +0000
Subject: * lib/prime.rb: Optimize Integer#prime?   Patch by Nick Slocum [Bug
 #10354]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52200 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 lib/prime.rb | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'lib/prime.rb')

diff --git a/lib/prime.rb b/lib/prime.rb
index c9575f6a2a..d99a51a967 100644
--- a/lib/prime.rb
+++ b/lib/prime.rb
@@ -31,7 +31,14 @@ class Integer
 
   # Returns true if +self+ is a prime number, else returns false.
   def prime?
-    Prime.prime?(self)
+    return self >= 2 if self <= 3
+    return false if self % 2 == 0 or self % 3 == 0
+    (5..(self**0.5).floor).step(6).each do |i|
+      if self % i == 0 || self % (i + 2) == 0
+        return false
+      end
+    end
+    true
   end
 
   # Iterates the given block over all prime numbers.
-- 
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