Generalize reduce() to work with iterators.
NEEDS DOC CHANGES.
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@ -385,4 +385,17 @@ class TestCase(unittest.TestCase):
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except OSError:
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pass
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# Test reduces()'s use of iterators.
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def test_builtin_reduce(self):
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from operator import add
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self.assertEqual(reduce(add, SequenceClass(5)), 10)
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self.assertEqual(reduce(add, SequenceClass(5), 42), 52)
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self.assertRaises(TypeError, reduce, add, SequenceClass(0))
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self.assertEqual(reduce(add, SequenceClass(0), 42), 42)
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self.assertEqual(reduce(add, SequenceClass(1)), 0)
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self.assertEqual(reduce(add, SequenceClass(1), 42), 42)
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d = {"one": 1, "two": 2, "three": 3}
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self.assertEqual(reduce(add, d), "".join(d.keys()))
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run_unittest(TestCase)
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@ -22,6 +22,7 @@ Core
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map()
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max()
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min()
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reduce()
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What's New in Python 2.1 (final)?
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@ -1851,26 +1851,25 @@ is printed without a trailing newline before reading.";
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static PyObject *
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builtin_reduce(PyObject *self, PyObject *args)
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{
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PyObject *seq, *func, *result = NULL;
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PySequenceMethods *sqf;
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register int i;
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PyObject *seq, *func, *result = NULL, *it;
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if (!PyArg_ParseTuple(args, "OO|O:reduce", &func, &seq, &result))
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return NULL;
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if (result != NULL)
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Py_INCREF(result);
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sqf = seq->ob_type->tp_as_sequence;
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if (sqf == NULL || sqf->sq_item == NULL) {
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it = PyObject_GetIter(seq);
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if (it == NULL) {
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PyErr_SetString(PyExc_TypeError,
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"reduce() arg 2 must be a sequence");
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"reduce() arg 2 must support iteration");
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Py_XDECREF(result);
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return NULL;
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}
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if ((args = PyTuple_New(2)) == NULL)
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goto Fail;
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for (i = 0; ; ++i) {
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for (;;) {
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PyObject *op2;
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if (args->ob_refcnt > 1) {
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@ -1879,12 +1878,18 @@ builtin_reduce(PyObject *self, PyObject *args)
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goto Fail;
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}
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if ((op2 = (*sqf->sq_item)(seq, i)) == NULL) {
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if (PyErr_ExceptionMatches(PyExc_IndexError)) {
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PyErr_Clear();
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break;
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op2 = PyIter_Next(it);
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if (op2 == NULL) {
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/* StopIteration is *implied* by a NULL return from
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* PyIter_Next() if PyErr_Occurred() is false.
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*/
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if (PyErr_Occurred()) {
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if (PyErr_ExceptionMatches(PyExc_StopIteration))
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PyErr_Clear();
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else
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goto Fail;
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}
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goto Fail;
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break;
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}
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if (result == NULL)
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@ -1903,11 +1908,13 @@ builtin_reduce(PyObject *self, PyObject *args)
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PyErr_SetString(PyExc_TypeError,
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"reduce() of empty sequence with no initial value");
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Py_DECREF(it);
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return result;
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Fail:
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Py_XDECREF(args);
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Py_XDECREF(result);
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Py_DECREF(it);
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return NULL;
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}
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