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gh-94906: Support multiple steps in math.nextafter (#103881)

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This PR updates `math.nextafter` to add a new `steps` argument. The behaviour is as though `math.nextafter` had been called `steps` times in succession.

---------

Co-authored-by: Mark Dickinson <mdickinson@enthought.com>
This commit is contained in:
Matthias Görgens 2023-05-20 04:03:49 +08:00 • committed by GitHub
parent c3f43bfb4b
commit 6e39fa1955
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10 changed files with 223 additions and 18 deletions
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20
Lib/test/test_math.py
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@ -2296,11 +2296,20 @@ class MathTests(unittest.TestCase):
float.fromhex('0x1.fffffffffffffp-1'))
self.assertEqual(math.nextafter(1.0, INF),
float.fromhex('0x1.0000000000001p+0'))
self.assertEqual(math.nextafter(1.0, -INF, steps=1),
float.fromhex('0x1.fffffffffffffp-1'))
self.assertEqual(math.nextafter(1.0, INF, steps=1),
float.fromhex('0x1.0000000000001p+0'))
self.assertEqual(math.nextafter(1.0, -INF, steps=3),
float.fromhex('0x1.ffffffffffffdp-1'))
self.assertEqual(math.nextafter(1.0, INF, steps=3),
float.fromhex('0x1.0000000000003p+0'))
# x == y: y is returned
self.assertEqual(math.nextafter(2.0, 2.0), 2.0)
self.assertEqualSign(math.nextafter(-0.0, +0.0), +0.0)
self.assertEqualSign(math.nextafter(+0.0, -0.0), -0.0)
for steps in range(1, 5):
self.assertEqual(math.nextafter(2.0, 2.0, steps=steps), 2.0)
self.assertEqualSign(math.nextafter(-0.0, +0.0, steps=steps), +0.0)
self.assertEqualSign(math.nextafter(+0.0, -0.0, steps=steps), -0.0)
# around 0.0
smallest_subnormal = sys.float_info.min * sys.float_info.epsilon
@ -2325,6 +2334,11 @@ class MathTests(unittest.TestCase):
self.assertIsNaN(math.nextafter(1.0, NAN))
self.assertIsNaN(math.nextafter(NAN, NAN))
self.assertEqual(1.0, math.nextafter(1.0, INF, steps=0))
with self.assertRaises(ValueError):
math.nextafter(1.0, INF, steps=-1)
@requires_IEEE_754
def test_ulp(self):
self.assertEqual(math.ulp(1.0), sys.float_info.epsilon)