infer_shape function for scan

theano/sandbox/scan_module/scan_op.py

@@ -149,6 +149,17 @@ class ScanOp(PureOp):
                 rval = rval ^ val
         return rval
 
+    def infer_shape(self, node, input_shapes):
+        for inp, inp_shp in izip(node.inputs, input_shapes):
+            assert inp_shp is None or len(inp_shp) == inp.type.ndim
+
+        n_outs = len(self.outputs)
+        if self.gpu:
+            return [(Shape_i(0)(o),) + x[1:] for o, x
+                    in izip(node.outputs, input_shapes[1: n_outs + 1])]
+        else:
+            return input_shapes[1: n_outs + 1]
+
     def make_thunk(self, node, storage_map, compute_map, no_recycling):
         pass