bpo-35606: Implement math.prod (GH-11359)
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 83dab12..d2f8d53 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -2494,6 +2494,172 @@
}
+/*[clinic input]
+math.prod
+
+ iterable: object
+ /
+ *
+ start: object(c_default="NULL") = 1
+
+Calculate the product of all the elements in the input iterable.
+
+The default start value for the product is 1.
+
+When the iterable is empty, return the start value. This function is
+intended specifically for use with numeric values and may reject
+non-numeric types.
+[clinic start generated code]*/
+
+static PyObject *
+math_prod_impl(PyObject *module, PyObject *iterable, PyObject *start)
+/*[clinic end generated code: output=36153bedac74a198 input=4c5ab0682782ed54]*/
+{
+ PyObject *result = start;
+ PyObject *temp, *item, *iter;
+
+ iter = PyObject_GetIter(iterable);
+ if (iter == NULL) {
+ return NULL;
+ }
+
+ if (result == NULL) {
+ result = PyLong_FromLong(1);
+ if (result == NULL) {
+ Py_DECREF(iter);
+ return NULL;
+ }
+ } else {
+ Py_INCREF(result);
+ }
+#ifndef SLOW_PROD
+ /* Fast paths for integers keeping temporary products in C.
+ * Assumes all inputs are the same type.
+ * If the assumption fails, default to use PyObjects instead.
+ */
+ if (PyLong_CheckExact(result)) {
+ int overflow;
+ long i_result = PyLong_AsLongAndOverflow(result, &overflow);
+ /* If this already overflowed, don't even enter the loop. */
+ if (overflow == 0) {
+ Py_DECREF(result);
+ result = NULL;
+ }
+ /* Loop over all the items in the iterable until we finish, we overflow
+ * or we found a non integer element */
+ while(result == NULL) {
+ item = PyIter_Next(iter);
+ if (item == NULL) {
+ Py_DECREF(iter);
+ if (PyErr_Occurred()) {
+ return NULL;
+ }
+ return PyLong_FromLong(i_result);
+ }
+ if (PyLong_CheckExact(item)) {
+ long b = PyLong_AsLongAndOverflow(item, &overflow);
+ long x = i_result * b;
+ /* Continue if there is no overflow */
+ if (overflow == 0
+ && x < INT_MAX && x > INT_MIN
+ && !(b != 0 && x / i_result != b)) {
+ i_result = x;
+ Py_DECREF(item);
+ continue;
+ }
+ }
+ /* Either overflowed or is not an int.
+ * Restore real objects and process normally */
+ result = PyLong_FromLong(i_result);
+ if (result == NULL) {
+ Py_DECREF(item);
+ Py_DECREF(iter);
+ return NULL;
+ }
+ temp = PyNumber_Multiply(result, item);
+ Py_DECREF(result);
+ Py_DECREF(item);
+ result = temp;
+ if (result == NULL) {
+ Py_DECREF(iter);
+ return NULL;
+ }
+ }
+ }
+
+ /* Fast paths for floats keeping temporary products in C.
+ * Assumes all inputs are the same type.
+ * If the assumption fails, default to use PyObjects instead.
+ */
+ if (PyFloat_CheckExact(result)) {
+ double f_result = PyFloat_AS_DOUBLE(result);
+ Py_DECREF(result);
+ result = NULL;
+ while(result == NULL) {
+ item = PyIter_Next(iter);
+ if (item == NULL) {
+ Py_DECREF(iter);
+ if (PyErr_Occurred()) {
+ return NULL;
+ }
+ return PyFloat_FromDouble(f_result);
+ }
+ if (PyFloat_CheckExact(item)) {
+ f_result *= PyFloat_AS_DOUBLE(item);
+ Py_DECREF(item);
+ continue;
+ }
+ if (PyLong_CheckExact(item)) {
+ long value;
+ int overflow;
+ value = PyLong_AsLongAndOverflow(item, &overflow);
+ if (!overflow) {
+ f_result *= (double)value;
+ Py_DECREF(item);
+ continue;
+ }
+ }
+ result = PyFloat_FromDouble(f_result);
+ if (result == NULL) {
+ Py_DECREF(item);
+ Py_DECREF(iter);
+ return NULL;
+ }
+ temp = PyNumber_Multiply(result, item);
+ Py_DECREF(result);
+ Py_DECREF(item);
+ result = temp;
+ if (result == NULL) {
+ Py_DECREF(iter);
+ return NULL;
+ }
+ }
+ }
+#endif
+ /* Consume rest of the iterable (if any) that could not be handled
+ * by specialized functions above.*/
+ for(;;) {
+ item = PyIter_Next(iter);
+ if (item == NULL) {
+ /* error, or end-of-sequence */
+ if (PyErr_Occurred()) {
+ Py_DECREF(result);
+ result = NULL;
+ }
+ break;
+ }
+ temp = PyNumber_Multiply(result, item);
+ Py_DECREF(result);
+ Py_DECREF(item);
+ result = temp;
+ if (result == NULL)
+ break;
+ }
+ Py_DECREF(iter);
+ return result;
+}
+
+
static PyMethodDef math_methods[] = {
{"acos", math_acos, METH_O, math_acos_doc},
{"acosh", math_acosh, METH_O, math_acosh_doc},
@@ -2541,6 +2707,7 @@
{"tan", math_tan, METH_O, math_tan_doc},
{"tanh", math_tanh, METH_O, math_tanh_doc},
MATH_TRUNC_METHODDEF
+ MATH_PROD_METHODDEF
{NULL, NULL} /* sentinel */
};