* lib/cmath.rb (CMath.cbrt): returns the principal value of the cube

root of the argument.  fix #3676
* test/test_cmath.rb (test_cbrt_returns_principal_value_of_cube_root):
  test for the above change.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32047 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Mon Jun 13 14:35:00 2011  Kenta Murata  <mrkn@mrkn.jp>
+
+	* lib/cmath.rb (CMath.cbrt): returns the principal value of the cube
+	  root of the argument.  fix #3676
+
+	* test/test_cmath.rb (test_cbrt_returns_principal_value_of_cube_root):
+	  test for the above change.
+
 Mon Jun 13 14:17:00 2011  Kenta Murata  <mrkn@mrkn.jp>
 
 	* lib/test/unit.rb (Test::Unit::GlobOption#non_options): fix typo.

lib/cmath.rb

@@ -122,13 +122,9 @@ module CMath
   end
 
   ##
-  # returns the cube root of +z+
+  # returns the principal value of the cube root of +z+
   def cbrt(z)
-    if z.real?
+    Complex(z) ** (1.0/3)
-      cbrt!(z)
-    else
-      Complex(z) ** (1.0/3)
-    end
   end
 
   ##

test/test_cmath.rb

@@ -5,4 +5,8 @@ class TestCMath < Test::Unit::TestCase
   def test_sqrt
     assert_equal CMath.sqrt(1.0.i), CMath.sqrt(1.i), '[ruby-core:31672]'
   end
+
+  def test_cbrt_returns_principal_value_of_cube_root
+    assert_equal CMath.cbrt(-8), (-8)**(1.0/3), '#3676'
+  end
 end