--- a/dataset.py	Fri May 09 17:38:57 2008 -0400
+++ b/dataset.py	Mon May 12 14:30:21 2008 -0400
@@ -429,8 +429,8 @@
         rows=None
         # or a slice
         if type(i) is slice:
-            if not i.start: i.start=0
-            if not i.step: i.step=1
+            if not i.start: i=slice(0,i.stop,i.step)
+            if not i.step: i=slice(i.start,i.stop,1)
             if i.step is 1:
                 return self.minibatches(minibatch_size=i.stop-i.start,n_batches=1,offset=i.start).next().examples()
             rows = range(i.start,i.stop,i.step)
@@ -497,7 +497,7 @@
         dataset1 | dataset2 returns a dataset whose list of fields is the concatenation of the list of
         fields of the argument datasets. This only works if they all have the same length.
         """
-        return HStackedDataSet(self,other)
+        return HStackedDataSet([self,other])
 
     def __and__(self,other):
         """
@@ -505,7 +505,7 @@
         (and whose length is the sum of the length of the argument datasets). This only
         works if they all have the same fields.
         """
-        return VStackedDataSet(self,other)
+        return VStackedDataSet([self,other])
 
 def hstack(datasets):
     """
@@ -1068,7 +1068,7 @@
           def next(self):
               upper = self.current+minibatch_size
               cache_len = len(self.dataset.cached_examples)
-              if upper>=cache_len: # whole minibatch is not already in cache
+              if upper>cache_len: # whole minibatch is not already in cache
                   # cache everything from current length to upper
                   for example in self.dataset.source_dataset[cache_len:upper]:
                       self.dataset.cached_examples.append(example)