Fourier-related transformations of mathematical functions.
These functions are written for simplicity and correctness, not speed. If you need a fast FFT implementation for your application, you should strongly consider using a library of FFTW bindings instead.
Discrete cosine transform
Discrete cosine transform (DCT-II). Only real part of vector is transformed, imaginary part is ignored.
Inverse discrete cosine transform (DCT-III). It's inverse of
dct only up to scale parameter:
(idct . dct) x = (* lenngth x)
Inverse discrete cosine transform (DCT-III). Only real part of vector is transformed, imaginary part is ignored.