[Discuss-gnuradio] shift param in FFT block in GRC

[John Shields]

When I add a FFT block in the GRC (gr_fft_vxx if I understand things 
correctly) I am offered a boolean parameter 'shift'. When I attempt to 
discern the code, there is a comment:

   // apply a fft shift on the data  - for the fwd FFT and
   // apply an ifft shift on the data  - for reverse.

What does this parameter do?

                Kind Regards,

                        John