RosettaCodeData/Task/Fast-Fourier-transform/J/fast-fourier-transform-1.j

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2013-04-10 21:29:02 -07:00
cube =: ($~ q:@#) :. ,
rou =: ^@j.@o.@(% #)@i.@-: NB. roots of unity
floop =: 4 : 'for_r. i.#$x do. (y=.{."1 y) ] x=.(+/x) ,&,:"r (-/x)*y end.'
fft =: ] floop&.cube rou@#