fft_c2c                 Discrete Fourier transforms
fft_dct                 Discrete cosine and sine transforms
fft_freq                Sample frequencies
fft_next_len            Fast transform lengths
fft_shift               Shift the zero frequency to the centre
fft_stats               Drop-in replacements for stats::fft() and
                        stats::mvfft()
fft_workers             Threads per transform
zufft_info              Information about the zufft build
