Some type Conversions

      gr_float_to_short        (1 float in, 1 short out [saturate])
      gr_short_to_float        (1 short in, 1 float out)
      gr_float_to_complex      (1 or 2 floats in, 1 complex out)
      gr_complex_to_float      (1 complex in, 1 or 2 floats out)
      gr_complex_to_real       (1 complex in, 1 float out)
      gr_complex_to_imag       (1 complex in, 1 float out)
      gr_complex_to_mag        (1 complex in, 1 float out)
      gr_complex_to_arg        (1 complex in, 1 float out)