Issue 1678380: fix a bug identifying -0.0 and 0.0
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@ -99,6 +99,27 @@ class IEEEFormatTestCase(unittest.TestCase):
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('<f', LE_FLOAT_NAN)]:
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struct.unpack(fmt, data)
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if float.__getformat__("double").startswith("IEEE"):
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def test_negative_zero(self):
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import math
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def pos_pos():
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return 0.0, math.atan2(0.0, -1)
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def pos_neg():
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return 0.0, math.atan2(-0.0, -1)
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def neg_pos():
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return -0.0, math.atan2(0.0, -1)
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def neg_neg():
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return -0.0, math.atan2(-0.0, -1)
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self.assertEquals(pos_pos(), neg_pos())
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self.assertEquals(pos_neg(), neg_neg())
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if float.__getformat__("double").startswith("IEEE"):
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def test_underflow_sign(self):
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import math
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# check that -1e-1000 gives -0.0, not 0.0
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self.assertEquals(math.atan2(-1e-1000, -1), math.atan2(-0.0, -1))
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self.assertEquals(math.atan2(float('-1e-1000'), -1),
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math.atan2(-0.0, -1))
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def test_main():
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test_support.run_unittest(
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@ -12,6 +12,9 @@ What's New in Python 2.5.2c1?
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Core and builtins
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-----------------
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- Issue #1678380: distinction between 0.0 and -0.0 was lost during constant
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folding optimization. This was a regression from Python 2.4.
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- Issue #1882: when compiling code from a string, encoding cookies in the
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second line of code were not always recognized correctly.
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@ -1567,7 +1567,20 @@ compiler_add_o(struct compiler *c, PyObject *dict, PyObject *o)
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Py_ssize_t arg;
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/* necessary to make sure types aren't coerced (e.g., int and long) */
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t = PyTuple_Pack(2, o, o->ob_type);
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/* _and_ to distinguish 0.0 from -0.0 e.g. on IEEE platforms */
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if (PyFloat_Check(o)) {
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double d = PyFloat_AS_DOUBLE(o);
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unsigned char* p = (unsigned char*) &d;
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/* all we need is to make the tuple different in either the 0.0
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* or -0.0 case from all others, just to avoid the "coercion".
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*/
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if (*p==0 && p[sizeof(double)-1]==0)
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t = PyTuple_Pack(3, o, o->ob_type, Py_None);
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else
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t = PyTuple_Pack(2, o, o->ob_type);
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} else {
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t = PyTuple_Pack(2, o, o->ob_type);
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}
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if (t == NULL)
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return -1;
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