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Issue #2138: Add math.factorial().

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This commit is contained in:
Raymond Hettinger 2008-06-09 06:54:45 +00:00
parent dd96db63f6
commit ecbdd2e9b0
4 changed files with 71 additions and 0 deletions
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50
Modules/mathmodule.c
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@ -512,6 +512,55 @@ PyDoc_STRVAR(math_sum_doc,
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 @@ static PyMethodDef math_methods[] = {
{"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},