--- a/dataset.py	Mon May 12 14:11:57 2008 -0400
+++ b/dataset.py	Mon May 12 14:13:19 2008 -0400
@@ -765,12 +765,16 @@
                 return self
             def next(self):
                 # concatenate all the fields of the minibatches
+                l=LookupList()
+                for iter in self.iterators:
+                    l.append_lookuplist(iter.next())
+                return l
                 return reduce(LookupList.__add__,[iterator.next() for iterator in self.iterators])
                                      
         assert self.hasFields(*fieldnames)
         # find out which underlying datasets are necessary to service the required fields
         # and construct corresponding minibatch iterators
-        if fieldnames:
+        if fieldnames and fieldnames!=self.fieldNames():
             datasets=set([])
             fields_in_dataset=dict([(dataset,[]) for dataset in datasets])
             for fieldname in fieldnames: