Hi all,

Thanks a lot. After the corrections in the attached file, I still get the following.

Traceback (most recent call last):
  File "<stdin>", line 21, in <module>
  File "/Users/master/firedrake/lib/python2.7/site-packages/firedrake/io.py", line 110, in __lshift__
    self._file << data
  File "/Users/master/firedrake/lib/python2.7/site-packages/firedrake/io.py", line 524, in __lshift__
    self._update_PVD(data)
  File "/Users/master/firedrake/lib/python2.7/site-packages/firedrake/io.py", line 542, in _update_PVD
    new_vtk << function
  File "/Users/master/firedrake/lib/python2.7/site-packages/firedrake/io.py", line 180, in __lshift__
    mesh = function.function_space().mesh()
AttributeError: 'Sum' object has no attribute 'function_space'