radix-2 fast Fourier transform
Package fft provides a fast discrete Fourier transformation algorithm.
Implemented is the 1-dimensional DFT of complex input data for with input lengths which are powers of 2.
The algorithm is non-recursive and works in-place overwriting the input array.
Before doing the transform on acutal data, allocate an FFT object with t := fft.New(N) where N is the length of the input array. Then multiple calls to t.Transform(x) can be done with different input vectors having the same length.