[Checkins] SVN: BTrees/branches/pure_python/ weightedUnion must work even when merging is impossible (e.g. two sets).

[Tres Seaver]

Log message for revision 128514:
  weightedUnion must work even when merging is impossible (e.g. two sets).

Changed:
  _U  BTrees/branches/pure_python/
  U   BTrees/branches/pure_python/BTrees/_base.py

-=-
Modified: BTrees/branches/pure_python/BTrees/_base.py
===================================================================
--- BTrees/branches/pure_python/BTrees/_base.py	2012-12-04 20:46:34 UTC (rev 128513)
+++ BTrees/branches/pure_python/BTrees/_base.py	2012-12-04 20:46:35 UTC (rev 128514)
@@ -1237,7 +1237,6 @@
     MERGE_DEFAULT = getattr(o1, 'MERGE_DEFAULT', None)
     i1 = _SetIteration(o1, True, MERGE_DEFAULT)
     i2 = _SetIteration(o2, True, MERGE_DEFAULT)
-    result = o1._mapping_type()
     MERGE = getattr(o1, 'MERGE', None)
     if MERGE is None and i1.useValues and i2.useValues:
         raise TypeError("invalid set operation")
@@ -1251,9 +1250,16 @@
                 raise TypeError("invalid set operation")
         else:
             raise TypeError("invalid set operation")
-    def copy(i, w):
-        result._keys.append(i.key)
-        result._values.append(MERGE_WEIGHT(i.value, w))
+    _merging = i1.useValues or i2.useValues
+    if _merging:
+        result = o1._mapping_type()
+        def copy(i, w):
+            result._keys.append(i.key)
+            result._values.append(MERGE_WEIGHT(i.value, w))
+    else:
+        result = o1._set_type()
+        def copy(i, w):
+            result._keys.append(i.key)
 
     while i1.active and i2.active:
         cmp_ = cmp(i1.key, i2.key)
@@ -1262,7 +1268,8 @@
             i1.advance()
         elif cmp_ == 0:
             result._keys.append(i1.key)
-            result._values.append(MERGE(i1.value, w1, i2.value, w2))
+            if _merging:
+                result._values.append(MERGE(i1.value, w1, i2.value, w2))
             i1.advance()
             i2.advance()
         else: