[Discuss-gnuradio] How to specify a complex number in block: vector_source ?

Dear Sir,

I am using the built-in block of Vector Source, configured as below:

  Output Type = Complex.

  Vector = ( 1, 2, 3 )

Then I run the flow graph. 

The block sends out  1 + 0i,  2 + 0i, 3 + 0i.

Question:
How to make it sends 1 + 2i ?

(How to configure this at the Vector field?)

Regards,

activecat