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(slib.info)Fast Fourier Transform

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Fast Fourier Transform
======================

  `(require 'fft)'

 - Function: fft array
     ARRAY is an array of `(expt 2 n)' numbers.  `fft' returns an array
     of complex numbers comprising the "Discrete Fourier Transform" of
     ARRAY.

 - Function: fft-1 array
     `fft-1' returns an array of complex numbers comprising the inverse
     Discrete Fourier Transform of ARRAY.

  `(fft-1 (fft ARRAY))' will return an array of values close to ARRAY.

     (fft '#(1 0+i -1 0-i 1 0+i -1 0-i)) =>
     
     #(0.0 0.0 0.0+628.0783185208527e-18i 0.0
       0.0 0.0 8.0-628.0783185208527e-18i 0.0)
     
     (fft-1 '#(0 0 0 0 0 0 8 0)) =>
     
     #(1.0 -61.23031769111886e-18+1.0i -1.0 61.23031769111886e-18-1.0i
       1.0 -61.23031769111886e-18+1.0i -1.0 61.23031769111886e-18-1.0i)