Fix sloppy index() implementation:

- don't use min() and max()
- interpret negative start/stop argument like negative slice indices

Lib/test/test_types.py

@@ -364,18 +364,22 @@ b.insert(-2, "foo")
 b.insert(-200, "left")
 b.insert(200, "right")
 if b != ["left",-2,-1,0,0,"foo",1,2,"right"]: raise TestFailed, 'list insert2'
+# a = [-2,-1,0,0,1,2]
 if a.count(0) != 2: raise TestFailed, ' list count'
 if a.index(0) != 2: raise TestFailed, 'list index'
 if a.index(0,2) != 2: raise TestFailed, 'list index, start argument'
-if a.index(-2,-10) != 0: raise TestFailed, 'list index, negative start argument'
+if a.index(0,-4) != 2: raise TestFailed, 'list index, -start argument'
+if a.index(-2,-10) != 0: raise TestFailed, 'list index, very -start argument'
 if a.index(0,3) != 3: raise TestFailed, 'list index, start argument'
+if a.index(0,-3) != 3: raise TestFailed, 'list index, -start argument'
 if a.index(0,3,4) != 3: raise TestFailed, 'list index, stop argument'
+if a.index(0,-3,-2) != 3: raise TestFailed, 'list index, -stop argument'
 try:
     a.index(2,0,-10)
 except ValueError:
     pass
 else:
-    raise TestFailed, 'list index, negative stop argument'
+    raise TestFailed, 'list index, very -stop argument'
 a.remove(0)
 try:
     a.index(2,0,4)

Objects/listobject.c

@@ -1834,8 +1834,18 @@ listindex(PyListObject *self, PyObject *args)
 
 	if (!PyArg_ParseTuple(args, "O|ii:index", &v, &start, &stop))
 		return NULL;
-	start = max(0, start);
-	stop = max(0, min(self->ob_size, stop));
+	if (start < 0) {
+		start += self->ob_size;
+		if (start < 0)
+			start = 0;
+	}
+	if (stop < 0) {
+		stop += self->ob_size;
+		if (stop < 0)
+			stop = 0;
+	}
+	else if (stop > self->ob_size)
+		stop = self->ob_size;
 	for (i = start; i < stop; i++) {
 		int cmp = PyObject_RichCompareBool(self->ob_item[i], v, Py_EQ);
 		if (cmp > 0)