2 files changed, 6 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index f85e186121..32c68c9416 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jun  9 22:38:09 2009  Tadayoshi Funaba  <[email protected]>
+
+	* lib/cmath.rb (log10): raised exception when the given number is
+	  a negative real.
+
 Tue Jun  9 15:13:14 2009  Nobuyoshi Nakada  <[email protected]>
 
 	* dir.c (dir_s_glob): fixed rdoc.  a patch from Joseph Pecoraro a
diff --git a/lib/cmath.rb b/lib/cmath.rb
index 5b261ed6a8..31c5a59c99 100644
--- a/lib/cmath.rb
+++ b/lib/cmath.rb
@@ -47,7 +47,7 @@ module CMath
   end
 
   def log10(z)
-    if z.real?
+    if z.real? and z >= 0
       log10!(z)
     else
       log(z) / log!(10)