Wrong FFT implementation

[ezamagni]

the fft and ifft implementations in complex-math.swift are wrong:

• the number of elements inside the input (real) array must be a power of 2 for the FFT to give correct results
• as stated at https://developer.apple.com/library/ios/documentation/Performance/Conceptual/vDSP_Programming_Guide/UsingFourierTransforms/UsingFourierTransforms.html the output of Accelerate fft functions must be re-scaled: you're already dividing by 2 the output of forward real transforms, while you should divide by n (not 2048) the output of inverse real transforms.

[stsievert]

Thank you. I'll look into this more, hopefully within the next week.