In both documents: fft(,) & ifft(,) are given as Smath stand alone.
Much faster is the Smath/Matlab: mwabs(mwfft(,)), mwfft(,).
Both Smath: fft(,) & ifft(,) can be collapsed in utilities.
Observe the two styles "stem": modular and open style.

Jean

Fourier fft Spectrum [STEM MODULE].sm (23 KiB) downloaded 118 time(s).

Fourier Revisit [fft STEM, ifft].sm (61 KiB) downloaded 102 time(s).