--- Python-2.6a3/Modules/cmathmoduleORIG.c	2008-04-20 11:30:05.000000000 -0700
+++ Python-2.6a3/Modules/cmathmodule.c	2008-05-10 16:34:28.000000000 -0700
@@ -1048,6 +1048,165 @@
 Checks if the real or imaginary part of z is infinite.");
 
 
+/* Summation function like function msum() in this Python recipe
+   <http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/393090>
+
+   See function math_sum() in file ./mathmodule.c for more details
+   and for the original code.  Make any changes in both places.
+*/
+
+static int
+_cmath_sum_add(double x, double y, double *s_ptr)
+{
+	double s;
+
+	errno = 0;
+	PyFPE_START_PROTECT("sum", return -1)
+	s = x + y;
+	PyFPE_END_PROTECT(s)
+	/* like math_2() in mathmodule.c */
+	if (Py_IS_NAN(s)) {
+		if (!Py_IS_NAN(x) && !Py_IS_NAN(y))
+			errno = EDOM;
+		else
+			errno = 0;
+	}
+	else if (Py_IS_INFINITY(s)) {
+		if (Py_IS_FINITE(x) && Py_IS_FINITE(y))
+			errno = ERANGE;
+		else
+			errno = 0;
+	}
+	if (errno != 0 && math_error() == NULL)
+		return -1;
+
+	*s_ptr = s;
+	return 0;
+}
+
+static int
+_cmath_sum_partial(double x, double **p_ptr, Py_ssize_t *n_ptr,
+                             double  *ps,    Py_ssize_t *m_ptr)
+{
+	Py_ssize_t i, j, n = *n_ptr, m = *m_ptr;
+	double y, hi, lo, *p = *p_ptr;
+
+	/* i = 0; for y in partials */
+	for (i = j = 0; j < n; j++) {
+		y = p[j];
+		if (_cmath_sum_add(x, y, &hi) < 0)
+			return -1;
+		lo = fabs(x) < fabs(y)
+		   ? x - (hi - y)
+		   : y - (hi - x);
+		if (lo != 0.0)
+			p[i++] = lo;
+		x = hi;
+	}
+	/* ps[i:] = [x] */
+	n = i;
+	if (n >= m) {  /* extend partials */
+		void *v = NULL;
+		m += m / 2;  /* plus 50% */
+		if (n < m && m < (PY_SSIZE_T_MAX / sizeof(double))) {
+			if (p == ps) {
+				v = PyMem_Malloc(sizeof(double) * m);
+				if (v != NULL)
+					memcpy(v, ps, sizeof(double) * n);
+			} else
+				v = PyMem_Realloc(p, sizeof(double) * m);
+		}
+		if (v == NULL) {  /* no memory or size overflow */
+			PyErr_SetString(PyExc_MemoryError, "math sum error");
+			return -1;
+		}
+		*p_ptr = p = (double*) v;
+		*m_ptr = m;
+	}
+	p[n++] = x;
+	*n_ptr = n;
+	return 0;
+}
+
+static PyObject*
+cmath_sum(PyObject *self, PyObject *args)
+{
+#	define CMATH_SUM_PS  128  /* static partials */
+
+	Py_complex c;
+	Py_ssize_t i, n_r = 0, m_r = CMATH_SUM_PS,
+	              n_i = 0, m_i = CMATH_SUM_PS;
+	double ps_r[CMATH_SUM_PS], *p_r = ps_r,
+	       ps_i[CMATH_SUM_PS], *p_i = ps_i;
+	PyObject *seq, *iter, *item, *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) { 
+		c = PyComplex_AsCComplex(sum);
+		sum = NULL;
+		if (PyErr_Occurred())
+			goto cmath_sum_exit;
+		p_r[n_r++] = c.real;
+		p_i[n_i++] = c.imag;
+	} else
+		p_r[0] = p_i[0] = 0.0;
+
+	/* for x in iterable */
+	for(;;) {
+		item = PyIter_Next(iter);
+		if (item == NULL) {
+			if (PyErr_Occurred())
+				goto cmath_sum_exit;
+			else
+				break;
+		}
+		c = PyComplex_AsCComplex(item);
+		Py_DECREF(item);
+		if (PyErr_Occurred())
+			goto cmath_sum_exit;
+		/* for y in partials */
+		if (_cmath_sum_partial(c.real, &p_r, &n_r, ps_r, &m_r) < 0 ||
+			_cmath_sum_partial(c.imag, &p_i, &n_i, ps_i, &m_i) < 0)
+			goto cmath_sum_exit;
+	}
+
+	/* sum(ps, 0.0) */
+	c.real = p_r[0];  /* always valid */
+	for (i = 1; i < n_r; i++) {
+		if (_cmath_sum_add(p_r[i], c.real, &c.real) < 0)
+			goto cmath_sum_exit;
+	}
+	c.imag = p_i[0];  /* always valid */
+	for (i = 1; i < n_i; i++) {
+		if (_cmath_sum_add(p_i[i], c.imag, &c.imag) < 0)
+			goto cmath_sum_exit;
+	}
+	sum = PyComplex_FromCComplex(c);
+
+cmath_sum_exit:
+	Py_DECREF(iter);
+	if (p_r != ps_r)
+		PyMem_Free(p_r);
+	if (p_i != ps_i)
+		PyMem_Free(p_i);
+	return sum;
+
+#	undef CMATH_SUM_PS
+}
+
+PyDoc_STRVAR(cmath_sum_doc,
+"sum(sequence[, start=0])\n"
+"\n"
+"Returns the full precision complex sum of a sequence of complex numbers plus the\n"
+"value of parameter 'start'.  When the sequence is empty, return complex start.");
+
+
 PyDoc_STRVAR(module_doc,
 "This module is always available. It provides access to mathematical\n"
 "functions for complex numbers.");
@@ -1072,6 +1231,7 @@
 	{"sin",    cmath_sin,   METH_VARARGS, c_sin_doc},
 	{"sinh",   cmath_sinh,  METH_VARARGS, c_sinh_doc},
 	{"sqrt",   cmath_sqrt,  METH_VARARGS, c_sqrt_doc},
+	{"sum",    cmath_sum,   METH_VARARGS, cmath_sum_doc},
 	{"tan",    cmath_tan,   METH_VARARGS, c_tan_doc},
 	{"tanh",   cmath_tanh,  METH_VARARGS, c_tanh_doc},
 	{NULL,		NULL}		/* sentinel */