Issue #2138: Add math.factorial().
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 5520ca9..7ace997 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -512,6 +512,55 @@
Return an accurate floating point sum of values in the iterable.\n\
Assumes IEEE-754 floating point arithmetic.");
+
+static PyObject *
+math_factorial(PyObject *self, PyObject *arg)
+{
+ long i, x;
+ PyObject *result, *iobj, *newresult;
+
+ if (PyFloat_Check(arg)) {
+ double dx = PyFloat_AS_DOUBLE((PyFloatObject *)arg);
+ if (dx != floor(dx)) {
+ PyErr_SetString(PyExc_ValueError,
+ "factorial() only accepts integral values");
+ return NULL;
+ }
+ }
+
+ x = PyInt_AsLong(arg);
+ if (x == -1 && PyErr_Occurred())
+ return NULL;
+ if (x < 0) {
+ PyErr_SetString(PyExc_ValueError,
+ "factorial() not defined for negative values");
+ return NULL;
+ }
+
+ result = (PyObject *)PyInt_FromLong(1);
+ if (result == NULL)
+ return NULL;
+ for (i=1 ; i<=x ; i++) {
+ iobj = (PyObject *)PyInt_FromLong(i);
+ if (iobj == NULL)
+ goto error;
+ newresult = PyNumber_Multiply(result, iobj);
+ Py_DECREF(iobj);
+ if (newresult == NULL)
+ goto error;
+ Py_DECREF(result);
+ result = newresult;
+ }
+ return result;
+
+error:
+ Py_DECREF(result);
+ Py_XDECREF(iobj);
+ return NULL;
+}
+
+PyDoc_STRVAR(math_factorial_doc, "Return n!");
+
static PyObject *
math_trunc(PyObject *self, PyObject *number)
{
@@ -949,6 +998,7 @@
{"degrees", math_degrees, METH_O, math_degrees_doc},
{"exp", math_exp, METH_O, math_exp_doc},
{"fabs", math_fabs, METH_O, math_fabs_doc},
+ {"factorial", math_factorial, METH_O, math_factorial_doc},
{"floor", math_floor, METH_O, math_floor_doc},
{"fmod", math_fmod, METH_VARARGS, math_fmod_doc},
{"frexp", math_frexp, METH_O, math_frexp_doc},