nextKeyAsSet(): Simplified the code. Added a new test to exercise it.

src/BTrees/SetOpTemplate.c

@@ -16,7 +16,7 @@
  Set operations
  ****************************************************************************/
 
-#define SETOPTEMPLATE_C "$Id: SetOpTemplate.c,v 1.18 2002/06/03 17:21:55 tim_one Exp $\n"
+#define SETOPTEMPLATE_C "$Id: SetOpTemplate.c,v 1.19 2002/06/03 17:45:08 tim_one Exp $\n"
 
 #ifdef INTSET_H
 static int 
@@ -49,18 +49,7 @@ nextIntSet(SetIteration *i)
 static int 
 nextKeyAsSet(SetIteration *i)
 {
-  /* XXX Looks like this block could be replaced by
-   * XXX   i->position = i->position == 0 ? 1 : -1;
-   */
-  if (i->position >= 0)
-    {
-      if (i->position < 1)
-        {
-          i->position ++;
-        }
-      else
-        i->position = -1;
-    }
+  i->position = i->position == 0 ? 1 : -1; 
   return 0;
 }
 #endif

src/BTrees/tests/testSetOps.py

@@ -69,6 +69,19 @@ class TestMultiUnion(TestCase):
         self.assertEqual(len(output), N*4)
         self.assertEqual(list(output), range(-N, 3*N))
 
+    def testFunkyKeyIteration(self):
+        # The internal set iteration protocol allows "iterating over" a
+        # a single key as if it were a set.
+        N = 100
+        slow = IISet()
+        for i in range(N):
+            slow = union(slow, IISet([i]))
+        fast = multiunion(range(N))  # acts like N distinct singleton sets
+        self.assertEqual(len(slow), N)
+        self.assertEqual(len(fast), N)
+        self.assertEqual(list(slow.keys()), list(fast.keys()))
+        self.assertEqual(list(fast.keys()), range(N))
+
 def test_suite():
     return makeSuite(TestMultiUnion, 'test')