Corrected axis verification.

theano/tensor/basic.py

@@ -3975,6 +3975,13 @@ def shape_padaxis(t, axis):
     """
     _t = as_tensor_variable(t)
 
+    ndim = _t.ndim + 1
+    if not -ndim <= axis < ndim:
+        msg = 'axis {0} is out of bounds [-{1}, {1})'.format(axis, ndim)
+        raise IndexError(msg)
+    if axis < 0:
+        axis += ndim
+
     pattern = [i for i in xrange(_t.type.ndim)]
     pattern.insert(axis, 'x')
     return DimShuffle(_t.broadcastable, pattern)(_t)
@@ -4028,13 +4035,6 @@ def stack(*tensors, **kwargs):
         raise Exception('tensors is empty. You should at least provide one'
                         ' tensor to theano.tensor.stack(tensors, axis).')
 
-    ndim = tensors[0].ndim + 1
-    if not -ndim <= axis < ndim:
-        msg = 'axis {0} is out of bounds [-{1}, {1})'.format(axis, ndim)
-        raise IndexError(msg)
-    if axis < 0:
-        axis += ndim
-
     # If all tensors are scalars of the same type, call make_vector.
     # It makes the graph simpler, by not adding DimShuffles and Rebroadcasts
 

theano/tensor/tests/test_basic.py

@@ -3461,13 +3461,13 @@ class T_Join_and_Split(unittest.TestCase):
         self.assertTrue(v3.shape == v4.shape)
         self.assertTrue(numpy.all(v3 == v4))
         # Testing negative axis
-        s = stack([a, b], axis=-1)
+        s = stack([a, b], axis=-2)
         f = function([a, b], s, mode=self.mode)
         v1 = [[1, 2, 3], [4, 5, 6]]
         v2 = [[7, 8, 9], [10, 11, 12]]
-        v = numpy.zeros((2, 3, 2))
-        v[:,:,0] = v1
-        v[:,:,1] = v2 
+        v = numpy.zeros((2, 2, 3))
+        v[:,0,:] = v1
+        v[:,1,:] = v2 
         out = f(v1, v2) 
         self.assertTrue(v.shape == out.shape)
         self.assertTrue(numpy.all(v == out))