Add test for tanh(-0.) == -0. on IEEE 754 systems

Lib/test/test_math.py

@@ -124,6 +124,59 @@ class MathTests(unittest.TestCase):
         self.ftest('atan2(1, 1)', math.atan2(1, 1), math.pi/4)
         self.ftest('atan2(1, 0)', math.atan2(1, 0), math.pi/2)
 
+        # math.atan2(0, x)
+        self.ftest('atan2(0., -inf)', math.atan2(0., NINF), math.pi)
+        self.ftest('atan2(0., -2.3)', math.atan2(0., -2.3), math.pi)
+        self.ftest('atan2(0., -0.)', math.atan2(0., -0.), math.pi)
+        self.assertEqual(math.atan2(0., 0.), 0.)
+        self.assertEqual(math.atan2(0., 2.3), 0.)
+        self.assertEqual(math.atan2(0., INF), 0.)
+        self.assert_(math.isnan(math.atan2(0., NAN)))
+        # math.atan2(-0, x)
+        self.ftest('atan2(-0., -inf)', math.atan2(-0., NINF), -math.pi)
+        self.ftest('atan2(-0., -2.3)', math.atan2(-0., -2.3), -math.pi)
+        self.ftest('atan2(-0., -0.)', math.atan2(-0., -0.), -math.pi)
+        self.assertEqual(math.atan2(-0., 0.), -0.)
+        self.assertEqual(math.atan2(-0., 2.3), -0.)
+        self.assertEqual(math.atan2(-0., INF), -0.)
+        self.assert_(math.isnan(math.atan2(-0., NAN)))
+        # math.atan2(INF, x)
+        self.ftest('atan2(inf, -inf)', math.atan2(INF, NINF), math.pi*3/4)
+        self.ftest('atan2(inf, -2.3)', math.atan2(INF, -2.3), math.pi/2)
+        self.ftest('atan2(inf, -0.)', math.atan2(INF, -0.0), math.pi/2)
+        self.ftest('atan2(inf, 0.)', math.atan2(INF, 0.0), math.pi/2)
+        self.ftest('atan2(inf, 2.3)', math.atan2(INF, 2.3), math.pi/2)
+        self.ftest('atan2(inf, inf)', math.atan2(INF, INF), math.pi/4)
+        self.assert_(math.isnan(math.atan2(INF, NAN)))
+        # math.atan2(NINF, x)
+        self.ftest('atan2(-inf, -inf)', math.atan2(NINF, NINF), -math.pi*3/4)
+        self.ftest('atan2(-inf, -2.3)', math.atan2(NINF, -2.3), -math.pi/2)
+        self.ftest('atan2(-inf, -0.)', math.atan2(NINF, -0.0), -math.pi/2)
+        self.ftest('atan2(-inf, 0.)', math.atan2(NINF, 0.0), -math.pi/2)
+        self.ftest('atan2(-inf, 2.3)', math.atan2(NINF, 2.3), -math.pi/2)
+        self.ftest('atan2(-inf, inf)', math.atan2(NINF, INF), -math.pi/4)
+        self.assert_(math.isnan(math.atan2(NINF, NAN)))
+        # math.atan2(+finite, x)
+        self.ftest('atan2(2.3, -inf)', math.atan2(2.3, NINF), math.pi)
+        self.ftest('atan2(2.3, -0.)', math.atan2(2.3, -0.), math.pi/2)
+        self.ftest('atan2(2.3, 0.)', math.atan2(2.3, 0.), math.pi/2)
+        self.assertEqual(math.atan2(2.3, INF), 0.)
+        self.assert_(math.isnan(math.atan2(2.3, NAN)))
+        # math.atan2(-finite, x)
+        self.ftest('atan2(-2.3, -inf)', math.atan2(-2.3, NINF), -math.pi)
+        self.ftest('atan2(-2.3, -0.)', math.atan2(-2.3, -0.), -math.pi/2)
+        self.ftest('atan2(-2.3, 0.)', math.atan2(-2.3, 0.), -math.pi/2)
+        self.assertEqual(math.atan2(-2.3, INF), -0.)
+        self.assert_(math.isnan(math.atan2(-2.3, NAN)))
+        # math.atan2(NAN, x)
+        self.assert_(math.isnan(math.atan2(NAN, NINF)))
+        self.assert_(math.isnan(math.atan2(NAN, -2.3)))
+        self.assert_(math.isnan(math.atan2(NAN, -0.)))
+        self.assert_(math.isnan(math.atan2(NAN, 0.)))
+        self.assert_(math.isnan(math.atan2(NAN, 2.3)))
+        self.assert_(math.isnan(math.atan2(NAN, INF)))
+        self.assert_(math.isnan(math.atan2(NAN, NAN)))
+
     def testCeil(self):
         self.assertRaises(TypeError, math.ceil)
         # These types will be int in py3k.
@@ -579,6 +632,11 @@ class MathTests(unittest.TestCase):
         self.ftest('tanh(inf)', math.tanh(INF), 1)
         self.ftest('tanh(-inf)', math.tanh(NINF), -1)
         self.assert_(math.isnan(math.tanh(NAN)))
+        # check that tanh(-0.) == -0. on IEEE 754 systems
+        if float.__getformat__("double").startswith("IEEE"):
+            self.assertEqual(math.tanh(-0.), -0.)
+            self.assertEqual(math.copysign(1., math.tanh(-0.)),
+                             math.copysign(1., -0.))
 
     def test_trunc(self):
         self.assertEqual(math.trunc(1), 1)