bpo-35431: Refactor math.comb() implementation. (GH-13725)

* Fixed some bugs.
* Added support for index-likes objects.
* Improved error messages.
* Cleaned up and optimized the code.
* Added more tests.

1 files changed, 6 insertions, 18 deletions

diff --git a/Modules/clinic/mathmodule.c.h b/Modules/clinic/mathmodule.c.h
index cba791e..92ec4be 100644
--- a/Modules/clinic/mathmodule.c.h
+++ b/Modules/clinic/mathmodule.c.h
@@ -639,10 +639,10 @@ exit:
 }
 
 PyDoc_STRVAR(math_comb__doc__,
-"comb($module, /, n, k)\n"
+"comb($module, n, k, /)\n"
 "--\n"
 "\n"
-"Number of ways to choose *k* items from *n* items without repetition and without order.\n"
+"Number of ways to choose k items from n items without repetition and without order.\n"
 "\n"
 "Also called the binomial coefficient. It is mathematically equal to the expression\n"
 "n! / (k! * (n - k)!). It is equivalent to the coefficient of k-th term in\n"
@@ -652,38 +652,26 @@ PyDoc_STRVAR(math_comb__doc__,
 "Raises ValueError if the arguments are negative or if k > n.");
 
 #define MATH_COMB_METHODDEF    \
-    {"comb", (PyCFunction)(void(*)(void))math_comb, METH_FASTCALL|METH_KEYWORDS, math_comb__doc__},
+    {"comb", (PyCFunction)(void(*)(void))math_comb, METH_FASTCALL, math_comb__doc__},
 
 static PyObject *
 math_comb_impl(PyObject *module, PyObject *n, PyObject *k);
 
 static PyObject *
-math_comb(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+math_comb(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    static const char * const _keywords[] = {"n", "k", NULL};
-    static _PyArg_Parser _parser = {NULL, _keywords, "comb", 0};
-    PyObject *argsbuf[2];
     PyObject *n;
     PyObject *k;
 
-    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 2, 2, 0, argsbuf);
-    if (!args) {
-        goto exit;
-    }
-    if (!PyLong_Check(args[0])) {
-        _PyArg_BadArgument("comb", 1, "int", args[0]);
+    if (!_PyArg_CheckPositional("comb", nargs, 2, 2)) {
         goto exit;
     }
     n = args[0];
-    if (!PyLong_Check(args[1])) {
-        _PyArg_BadArgument("comb", 2, "int", args[1]);
-        goto exit;
-    }
     k = args[1];
     return_value = math_comb_impl(module, n, k);
 
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=00aa76356759617a input=a9049054013a1b77]*/
+/*[clinic end generated code: output=6709521e5e1d90ec input=a9049054013a1b77]*/