Fix some compilation crash of the new GpuSubtensor

theano/sandbox/gpuarray/subtensor.py

+import StringIO
+
 import numpy
 
 import theano
-from theano import tensor
+from theano import tensor, gof
 from theano.tensor.subtensor import Subtensor, get_idx_list
 
 from theano.gof.python25 import all, any
@@ -21,7 +23,7 @@ class GpuSubtensor(HideC, Subtensor):
         otype = GpuArrayType(dtype=rval.outputs[0].type.dtype,
                              broadcastable=rval.outputs[0].type.broadcastable)
         x = as_gpuarray_variable(x)
-        return Apply(self, [x] + rval.inputs[1:], [otype()])
+        return gof.Apply(self, [x] + rval.inputs[1:], [otype()])
 
     def perform(self, node, inputs, out_):
         out, = out_
@@ -42,15 +44,16 @@ class GpuSubtensor(HideC, Subtensor):
         view_ndim = node.outputs[0].ndim
         indices = inputs[1:]
 
-        sio = StringIO.StringIO("""
+        sio = StringIO.StringIO()
+        print >> sio, """
         ssize_t %(name)s_starts[%(sz)s];
         ssize_t %(name)s_stops[%(sz)s];
         ssize_t %(name)s_steps[%(sz)s];
-        """ % dict(name=name, sz=len(self.idx_list)))
+        """ % dict(name=name, sz=len(self.idx_list))
 
         ndim = 0
         for i, idx in enumerate(self.idx_list):
-            if isinstance(idx, Type):
+            if isinstance(idx, gof.Type):
                 # Index by an input number
                 print >>sio, """
                 %(name)s_starts[%(i)s] = %(start)s;
@@ -58,12 +61,19 @@ class GpuSubtensor(HideC, Subtensor):
                 """ % dict(name=name, i=i, start=indices.pop(), step=0)
             elif isinstance(idx, slice):
                 # index by a fixed slice
+                step = idx.step
+                if step is None:
+                    step = 1
+                stop = idx.stop
+                if stop is None:
+                    #TODO find what is needed
+                    raise NotImplementedError("This case is not yet implemented!")
                 print >>sio, """
                 %(name)s_starts[%(i)s] = %(start)s;
                 %(name)s_stops[%(i)s] = %(stop)s;
                 %(name)s_steps[%(i)s] = %(step)s;
-                """ % dict(i=i, name=name, start=idx.start, stop=idx.stop,
-                           step=idx.step)
+                """ % dict(i=i, name=name, start=idx.start, stop=stop,
+                           step=step)
                 ndim += 1
             else:
                 # Index by a fixed number
@@ -77,13 +87,13 @@ class GpuSubtensor(HideC, Subtensor):
             // Try to reuse the python object.
             GpuArray_clear(&%(out)s->ga);
         } else {
-            %(out)s = new_GpuArray((PyObject *)&PyGpuArrayType, pygpu_default_context, Py_None);
+            %(out)s = new_GpuArray((PyObject *)&PyGpuArrayType, pygpu_default_context(), Py_None);
         }
         if (!%(out)s) { %(fail)s }
         int %(name)s_err;
         %(name)s_err = GpuArray_index(&%(out)s->ga, &%(inp)s->ga,
                                       %(name)s_starts, %(name)s_steps,
-                                      %(name)s_stops)
+                                      %(name)s_stops);
         if (%(name)s_err != GA_NO_ERROR) {
             Py_DECREF(%(out)s); %(out)s = NULL;
             PyErr_SetString(PyExc_RuntimeError, "Error during index");