--- bltinmodule.rev62728.trunk.c	2008-05-06 12:33:14.000000000 -0700
+++ bltinmodule3.c	2008-05-08 12:28:33.000000000 -0700
@@ -2221,6 +2221,7 @@
 static PyObject*
 builtin_sum(PyObject *self, PyObject *args)
 {
+#ifdef SLOW_SUM  /* Slow summation */
 	PyObject *seq;
 	PyObject *result = NULL;
 	PyObject *temp, *item, *iter;
@@ -2249,103 +2250,150 @@
 		Py_INCREF(result);
 	}
 
-#ifndef SLOW_SUM
-	/* Fast addition by keeping temporary sums in C instead of new Python objects.
-           Assumes all inputs are the same type.  If the assumption fails, default
-           to the more general routine.
-	*/
-	if (PyInt_CheckExact(result)) {
-		long i_result = PyInt_AS_LONG(result);
+	for(;;) {
+		item = PyIter_Next(iter);
+		if (item == NULL) {
+			/* error, or end-of-sequence */
+			if (PyErr_Occurred()) {
+				Py_DECREF(result);
+				result = NULL;
+			}
+			break;
+		}
+		temp = PyNumber_Add(result, item);
 		Py_DECREF(result);
-		result = NULL;
-		while(result == NULL) {
+		Py_DECREF(item);
+		result = temp;
+		if (result == NULL)
+			break;
+	}
+	Py_DECREF(iter);
+	return result;
+
+#else  /* Fast summation */
+	PyObject *seq, *iter, *item;
+	PyObject *sum = NULL;
+
+	if (!PyArg_UnpackTuple(args, "sum", 1, 2, &seq, &sum))
+		return NULL;
+
+	iter = PyObject_GetIter(seq);
+	if (iter == NULL)
+		return NULL;
+
+	if (sum == NULL) {
+		sum = PyInt_FromLong(0);
+		if (sum == NULL) {
+			Py_DECREF(iter);
+			return NULL;
+		}
+	} else {
+		/* reject string values for 'start' parameter */
+		if (PyObject_TypeCheck(sum, &PyBaseString_Type)) {
+			PyErr_SetString(PyExc_TypeError,
+				"sum() can't sum strings [use ''.join(seq) instead]");
+			Py_DECREF(iter);
+			return NULL;
+		}
+		Py_INCREF(sum);
+	}
+
+	/* get very first item as
+	   representative type */
+	item = PyIter_Next(iter);
+	if (item == NULL) {
+		Py_DECREF(iter);
+		if (PyErr_Occurred()) {
+			Py_DECREF(sum);
+			sum = NULL;
+		}
+		return sum;
+	}
+
+	/* keep adding ints */
+	if (PyInt_CheckExact(item) && PyInt_CheckExact(sum)) {
+		/* sum is most likely zero */
+		long i_sum = PyInt_AS_LONG(item);
+		Py_DECREF(item);
+		item = sum;
+		do {
+			long i = PyInt_AS_LONG(item);
+			if (i) {
+				long x = i_sum + i;
+				if ((x ^ i_sum) < 0 && (x ^ i) < 0)
+					break;  /* int overflow */
+				i_sum = x;
+			}
+			Py_DECREF(item);
 			item = PyIter_Next(iter);
 			if (item == NULL) {
 				Py_DECREF(iter);
 				if (PyErr_Occurred())
 					return NULL;
-				return PyInt_FromLong(i_result);
+				return PyInt_FromLong(i_sum);
 			}
-			if (PyInt_CheckExact(item)) {
-				long b = PyInt_AS_LONG(item);
-				long x = i_result + b;
-				if ((x^i_result) >= 0 || (x^b) >= 0) {
-					i_result = x;
-					Py_DECREF(item);
-					continue;
-				}
-			}
-			/* Either overflowed or is not an int. Restore real objects and process normally */
-			result = PyInt_FromLong(i_result);
-			temp = PyNumber_Add(result, item);
-			Py_DECREF(result);
+		} while (PyInt_CheckExact(item));
+		sum = PyInt_FromLong(i_sum);
+		if (sum == NULL) {
 			Py_DECREF(item);
-			result = temp;
-			if (result == NULL) {
-				Py_DECREF(iter);
-				return NULL;
-			}
+			Py_DECREF(iter);
+			return NULL;
 		}
 	}
 
-	if (PyFloat_CheckExact(result)) {
-		double f_result = PyFloat_AS_DOUBLE(result);
-		Py_DECREF(result);
-		result = NULL;
-		while(result == NULL) {
+	/* keep adding floats and ints */
+	if (PyFloat_CheckExact(item) && (PyFloat_CheckExact(sum) ||
+									 PyInt_CheckExact(sum))) {
+		double f, f_sum = PyFloat_AS_DOUBLE(item);
+		Py_DECREF(item);
+		item = sum;
+		for (;;) {
+			if (PyFloat_CheckExact(item))
+				f = PyFloat_AS_DOUBLE(item);
+			else if (PyInt_CheckExact(item))
+				f = (double)PyInt_AS_LONG(item);
+			else
+				break;
+			Py_DECREF(item);
+			PyFPE_START_PROTECT("add", Py_DECREF(iter); return NULL)
+			f_sum += f;
+			PyFPE_END_PROTECT(f_sum)
+
 			item = PyIter_Next(iter);
 			if (item == NULL) {
 				Py_DECREF(iter);
 				if (PyErr_Occurred())
 					return NULL;
-				return PyFloat_FromDouble(f_result);
-			}
-			if (PyFloat_CheckExact(item)) {
-				PyFPE_START_PROTECT("add", return 0)
-				f_result += PyFloat_AS_DOUBLE(item);
-				PyFPE_END_PROTECT(f_result)
-				Py_DECREF(item);
-				continue;
-			}
-			if (PyInt_CheckExact(item)) {
-				PyFPE_START_PROTECT("add", return 0)
-				f_result += (double)PyInt_AS_LONG(item);
-				PyFPE_END_PROTECT(f_result)
-				Py_DECREF(item);
-				continue;
+				return PyFloat_FromDouble(f_sum);
 			}
-			result = PyFloat_FromDouble(f_result);
-			temp = PyNumber_Add(result, item);
-			Py_DECREF(result);
+		}
+		sum = PyFloat_FromDouble(f_sum);
+		if (sum == NULL) {
 			Py_DECREF(item);
-			result = temp;
-			if (result == NULL) {
-				Py_DECREF(iter);
-				return NULL;
-			}
+			Py_DECREF(iter);
+			return NULL;
 		}
 	}
-#endif
 
-	for(;;) {
-		item = PyIter_Next(iter);
-		if (item == NULL) {
-			/* error, or end-of-sequence */
-			if (PyErr_Occurred()) {
-				Py_DECREF(result);
-				result = NULL;
-			}
-			break;
-		}
-		temp = PyNumber_Add(result, item);
-		Py_DECREF(result);
+	/* add any remaining items */
+	do {
+		PyObject *tmp = PyNumber_Add(sum, item);
 		Py_DECREF(item);
-		result = temp;
-		if (result == NULL)
-			break;
-	}
+		Py_DECREF(sum);
+		sum = tmp;
+		if (sum == NULL) {
+			Py_DECREF(iter);
+			return NULL;
+		}
+		item = PyIter_Next(iter);
+	} while (item != NULL);
 	Py_DECREF(iter);
-	return result;
+	if (PyErr_Occurred()) {
+		Py_DECREF(sum);
+		sum = NULL;
+	}
+	return sum;
+#endif
 }
 
 PyDoc_STRVAR(sum_doc,