Patch # 1507 by Mark Dickinson. Make complex(x, -0) retain the sign of

the imaginary part (as long as it's not complex).
Backport candidate?

1 files changed, 13 insertions, 0 deletions

diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index 3035c2d..64297e2 100644
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -9,6 +9,7 @@ warnings.filterwarnings(
 )
 
 from random import random
+from math import atan2
 
 # These tests ensure that complex math does the right thing
 
@@ -225,6 +226,18 @@ class ComplexTest(unittest.TestCase):
         self.assertAlmostEqual(complex(real=17+23j, imag=23), 17+46j)
         self.assertAlmostEqual(complex(real=1+2j, imag=3+4j), -3+5j)
 
+        # check that the sign of a zero in the real or imaginary part
+        # is preserved when constructing from two floats.  (These checks
+        # are harmless on systems without support for signed zeros.)
+        def split_zeros(x):
+            """Function that produces different results for 0. and -0."""
+            return atan2(x, -1.)
+
+        self.assertEqual(split_zeros(complex(1., 0.).imag), split_zeros(0.))
+        self.assertEqual(split_zeros(complex(1., -0.).imag), split_zeros(-0.))
+        self.assertEqual(split_zeros(complex(0., 1.).real), split_zeros(0.))
+        self.assertEqual(split_zeros(complex(-0., 1.).real), split_zeros(-0.))
+
         c = 3.14 + 1j
         self.assert_(complex(c) is c)
         del c