Oh FFT's are fun to play with. Is there a sci-nim repo I could add a PR too?
Here's a C version of the "Numerical Recipes" classic: <https://github.com/saulwiggin/Numerical-Recipies-in-C/blob/master/Chapter12.Fast-Fourier-Transforms/four1.c> Good reference for the maths: <https://faculty.washington.edu/seattle/brain-physics/FFT/numerical-recipes.pdf>
