R operator of Dot Op.

theano/tensor/basic.py

@@ -5102,6 +5102,16 @@ class Dot(Op):
             rval = dot(gz, y.T), dot(x.T, gz)
         return cast(rval[0], x.dtype), cast(rval[1], y.dtype)
 
+    def R_op(self, inputs, eval_points):
+        # R_op for a \dot b evaluted at c for a and d for b is
+        # simply c \dot b + a \dot d
+        if None in eval_points:
+            return [None]
+        t1 = self.make_node(eval_points[0], inputs[1]).outputs[0]
+        t2 = self.make_node(inputs[0], eval_points[1]).outputs[0]
+        return [t1+t2]
+
+
     def infer_shape(self, node, shapes):
         xshp, yshp = shapes
         x, y = node.inputs