From 73934b9da07daefb203e7d26089e7486a1ce4fdf Mon Sep 17 00:00:00 2001 From: Mark Dickinson Date: Sat, 18 May 2019 12:29:50 +0100 Subject: bpo-36887: add math.isqrt (GH-13244) * Add math.isqrt function computing the integer square root. * Code cleanup: remove redundant comments, rename some variables. * Tighten up code a bit more; use Py_XDECREF to simplify error handling. * Update Modules/mathmodule.c Co-Authored-By: Serhiy Storchaka * Update Modules/mathmodule.c Use real argument clinic type instead of an alias Co-Authored-By: Serhiy Storchaka * Add proof sketch * Updates from review. * Correct and expand documentation. * Fix bad reference handling on error; make some variables block-local; other tidying. * Style and consistency fixes. * Add missing error check; don't try to DECREF a NULL a * Simplify some error returns. * Another two test cases: - clarify that floats are rejected even if they happen to be squares of small integers - TypeError beats ValueError for a negative float * Documentation and markup improvements; thanks Serhiy for the suggestions! * Cleaner Misc/NEWS entry wording. * Clean up (with one fix) to the algorithm explanation and proof. --- Lib/test/test_math.py | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) (limited to 'Lib/test/test_math.py') diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py index cb05dee0e0..a11a344785 100644 --- a/Lib/test/test_math.py +++ b/Lib/test/test_math.py @@ -912,6 +912,57 @@ class MathTests(unittest.TestCase): self.assertEqual(math.dist(p, q), 5*scale) self.assertEqual(math.dist(q, p), 5*scale) + def testIsqrt(self): + # Test a variety of inputs, large and small. + test_values = ( + list(range(1000)) + + list(range(10**6 - 1000, 10**6 + 1000)) + + [3**9999, 10**5001] + ) + + for value in test_values: + with self.subTest(value=value): + s = math.isqrt(value) + self.assertIs(type(s), int) + self.assertLessEqual(s*s, value) + self.assertLess(value, (s+1)*(s+1)) + + # Negative values + with self.assertRaises(ValueError): + math.isqrt(-1) + + # Integer-like things + s = math.isqrt(True) + self.assertIs(type(s), int) + self.assertEqual(s, 1) + + s = math.isqrt(False) + self.assertIs(type(s), int) + self.assertEqual(s, 0) + + class IntegerLike(object): + def __init__(self, value): + self.value = value + + def __index__(self): + return self.value + + s = math.isqrt(IntegerLike(1729)) + self.assertIs(type(s), int) + self.assertEqual(s, 41) + + with self.assertRaises(ValueError): + math.isqrt(IntegerLike(-3)) + + # Non-integer-like things + bad_values = [ + 3.5, "a string", decimal.Decimal("3.5"), 3.5j, + 100.0, -4.0, + ] + for value in bad_values: + with self.subTest(value=value): + with self.assertRaises(TypeError): + math.isqrt(value) def testLdexp(self): self.assertRaises(TypeError, math.ldexp) -- cgit v1.2.1