FFT < test.dat
# Fast Fourier Transform
# k real imaginary power
0 4.000000 0.000000 16.000000
1 1.000000 -2.414214 6.828427
2 0.000000 0.000000 0.000000
3 1.000000 -0.414214 1.171573
4 0.000000 0.000000 0.000000
5 1.000000 0.414214 1.171573
6 0.000000 0.000000 0.000000
7 1.000000 2.414214 6.828427
# inverse Fast Fourier Transform
# k real imaginary
0 1.000000 0.000000
1 1.000000 -0.000000
2 1.000000 0.000000
3 1.000000 -0.000000
4 0.000000 0.000000
5 0.000000 0.000000
6 0.000000 -0.000000
7 0.000000 0.000000