merges r23658 from trunk into ruby_1_9_1.

--
	* lib/cmath.rb (log10): raised exception when the given number is
	  a negative real.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_1@23780 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/cmath.rb b/lib/cmath.rb
index 95a30c336b..1b0c65c995 100644
--- a/lib/cmath.rb
+++ b/lib/cmath.rb
@@ -48,7 +48,7 @@ module CMath
   end
 
   def log10(z)
-    if z.real?
+    if z.real? and z >= 0
       log10!(z)
     else
       log(z) / log!(10)