Merged revisions 87032 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r87032 | mark.dickinson | 2010-12-04 12:25:30 +0000 (Sat, 04 Dec 2010) | 3 lines

  Issue #10596: Fix float.__mod__ to have the same behaviour as
  float.__divmod__ with respect to signed zeros.
........
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
index fd8436a..6d90637 100644
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -231,6 +231,26 @@
             self.assertTrue(d == d, "{%r : None} not equal to itself" % f)
 
 
+    @requires_IEEE_754
+    def test_float_mod(self):
+        # Check behaviour of % operator for IEEE 754 special cases.
+        # In particular, check signs of zeros.
+        mod = operator.mod
+
+        self.assertEqualAndEqualSign(mod(-1.0, 1.0), 0.0)
+        self.assertEqualAndEqualSign(mod(-1e-100, 1.0), 1.0)
+        self.assertEqualAndEqualSign(mod(-0.0, 1.0), 0.0)
+        self.assertEqualAndEqualSign(mod(0.0, 1.0), 0.0)
+        self.assertEqualAndEqualSign(mod(1e-100, 1.0), 1e-100)
+        self.assertEqualAndEqualSign(mod(1.0, 1.0), 0.0)
+
+        self.assertEqualAndEqualSign(mod(-1.0, -1.0), -0.0)
+        self.assertEqualAndEqualSign(mod(-1e-100, -1.0), -1e-100)
+        self.assertEqualAndEqualSign(mod(-0.0, -1.0), -0.0)
+        self.assertEqualAndEqualSign(mod(0.0, -1.0), -0.0)
+        self.assertEqualAndEqualSign(mod(1e-100, -1.0), -1.0)
+        self.assertEqualAndEqualSign(mod(1.0, -1.0), -0.0)
+
 
 class FormatFunctionsTestCase(unittest.TestCase):