* lib/prime.rb (Prime#prime?): negative numbers can't be primes

  by definition. reported by Ivan Kataitsev. [Bug #7395]
* test/test_prime.rb: add test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45878 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 8 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 5cadb8dec6..7b44079fc4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri May  9 03:07:09 2014  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
+
+	* lib/prime.rb (Prime#prime?): negative numbers can't be primes
+	  by definition. reported by Ivan Kataitsev. [Bug #7395]
+	* test/test_prime.rb: add test.
+
 Thu May  8 14:34:29 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* class.c (rb_mod_init_copy): always clear instance variable,
diff --git a/lib/prime.rb b/lib/prime.rb
index f359c12693..6d3936e317 100644
--- a/lib/prime.rb
+++ b/lib/prime.rb
@@ -157,7 +157,6 @@ class Prime
   # +value+:: an arbitrary integer to be checked.
   # +generator+:: optional. A pseudo-prime generator.
   def prime?(value, generator = Prime::Generator23.new)
-    value = -value if value < 0
     return false if value < 2
     for num in generator
       q,r = value.divmod num
diff --git a/test/test_prime.rb b/test/test_prime.rb
index e89952948c..885406f9bd 100644
--- a/test/test_prime.rb
+++ b/test/test_prime.rb
@@ -141,8 +141,8 @@ class TestPrime < Test::Unit::TestCase
 
       # negative
       assert !-1.prime?
-      assert(-2.prime?)
-      assert(-3.prime?)
+      assert !-2.prime?
+      assert !-3.prime?
       assert !-4.prime?
     end
   end