Added missing line in example in the documentation.

doc/library/scan.txt

@@ -37,6 +37,9 @@ The equivalent Theano code would be:
 
 .. code-block:: python
 
+  k = T.iscalar("k")
+  A = T.vector("A")
+
   # Symbolic description of the result
   result, updates = theano.scan(fn=lambda prior_result, A: prior_result * A,
                                 outputs_info=T.ones_like(A),
@@ -50,6 +53,9 @@ The equivalent Theano code would be:
 
   # compiled function that returns A**k
   power = theano.function(inputs=[A,k], outputs=final_result, updates=updates)
+  
+  print power(range(10),2)
+  print power(range(10),4)
 
 Let us go through the example line by line. What we did is first to
 construct a function (using a lambda expression) that given ``prior_result`` and