bpo-37178: Allow a one argument form of math.perm() (GH-13905)
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@ -210,7 +210,7 @@ Number-theoretic and representation functions
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of *x* and are floats.
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.. function:: perm(n, k)
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.. function:: perm(n, k=None)
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Return the number of ways to choose *k* items from *n* items
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without repetition and with order.
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@ -218,6 +218,9 @@ Number-theoretic and representation functions
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Evaluates to ``n! / (n - k)!`` when ``k <= n`` and evaluates
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to zero when ``k > n``.
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If *k* is not specified or is None, then *k* defaults to *n*
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and the function returns ``n!``.
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Raises :exc:`TypeError` if either of the arguments are not integers.
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Raises :exc:`ValueError` if either of the arguments are negative.
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@ -1885,8 +1885,13 @@ class IsCloseTests(unittest.TestCase):
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self.assertEqual(perm(n, 1), n)
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self.assertEqual(perm(n, n), factorial(n))
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# Test one argument form
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for n in range(20):
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self.assertEqual(perm(n), factorial(n))
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self.assertEqual(perm(n, None), factorial(n))
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# Raises TypeError if any argument is non-integer or argument count is
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# not 2
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# not 1 or 2
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self.assertRaises(TypeError, perm, 10, 1.0)
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self.assertRaises(TypeError, perm, 10, decimal.Decimal(1.0))
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self.assertRaises(TypeError, perm, 10, "1")
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@ -1894,7 +1899,7 @@ class IsCloseTests(unittest.TestCase):
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self.assertRaises(TypeError, perm, decimal.Decimal(10.0), 1)
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self.assertRaises(TypeError, perm, "10", 1)
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self.assertRaises(TypeError, perm, 10)
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self.assertRaises(TypeError, perm)
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self.assertRaises(TypeError, perm, 10, 1, 3)
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self.assertRaises(TypeError, perm)
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@ -0,0 +1,2 @@
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For math.perm(n, k), let k default to n, giving the same result as
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factorial.
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@ -0,0 +1,2 @@
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Give math.perm() a one argument form that means the same as
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math.factorial().
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@ -639,7 +639,7 @@ exit:
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}
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PyDoc_STRVAR(math_perm__doc__,
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"perm($module, n, k, /)\n"
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"perm($module, n, k=None, /)\n"
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"--\n"
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"\n"
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"Number of ways to choose k items from n items without repetition and with order.\n"
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@ -647,6 +647,9 @@ PyDoc_STRVAR(math_perm__doc__,
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"Evaluates to n! / (n - k)! when k <= n and evaluates\n"
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"to zero when k > n.\n"
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"\n"
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"If k is not specified or is None, then k defaults to n\n"
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"and the function returns n!.\n"
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"\n"
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"Raises TypeError if either of the arguments are not integers.\n"
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"Raises ValueError if either of the arguments are negative.");
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@ -661,13 +664,17 @@ math_perm(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
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{
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PyObject *return_value = NULL;
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PyObject *n;
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PyObject *k;
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PyObject *k = Py_None;
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if (!_PyArg_CheckPositional("perm", nargs, 2, 2)) {
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if (!_PyArg_CheckPositional("perm", nargs, 1, 2)) {
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goto exit;
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}
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n = args[0];
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if (nargs < 2) {
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goto skip_optional;
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}
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k = args[1];
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skip_optional:
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return_value = math_perm_impl(module, n, k);
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exit:
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@ -713,4 +720,4 @@ math_comb(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
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exit:
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return return_value;
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}
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/*[clinic end generated code: output=5004266613284dcc input=a9049054013a1b77]*/
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/*[clinic end generated code: output=0eb1e76a769cdd30 input=a9049054013a1b77]*/
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@ -3002,7 +3002,7 @@ math_prod_impl(PyObject *module, PyObject *iterable, PyObject *start)
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math.perm
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n: object
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k: object
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k: object = None
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/
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Number of ways to choose k items from n items without repetition and with order.
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@ -3010,18 +3010,24 @@ Number of ways to choose k items from n items without repetition and with order.
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Evaluates to n! / (n - k)! when k <= n and evaluates
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to zero when k > n.
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If k is not specified or is None, then k defaults to n
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and the function returns n!.
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Raises TypeError if either of the arguments are not integers.
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Raises ValueError if either of the arguments are negative.
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[clinic start generated code]*/
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static PyObject *
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math_perm_impl(PyObject *module, PyObject *n, PyObject *k)
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/*[clinic end generated code: output=e021a25469653e23 input=b2e7729d9a1949cf]*/
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/*[clinic end generated code: output=e021a25469653e23 input=5311c5a00f359b53]*/
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{
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PyObject *result = NULL, *factor = NULL;
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int overflow, cmp;
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long long i, factors;
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if (k == Py_None) {
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return math_factorial(module, n);
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}
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n = PyNumber_Index(n);
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if (n == NULL) {
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return NULL;
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