(Comp.sys.handhelds) Option:
Item: 2090 by jurjen at cwi.nl
Author: [Jurjen NE Bos]
  Subj: HP28/48: Very FFT
  Date: Mon Feb 18 1991

A few friends asked me to write an FFT (fast fourier transform; converts a
vector to its "frequency diagram") program.  Looking through my archives, I
could not find any, although I vaguely remember another program was posted.
This program is written with speed in mind.  Most computations are done with
vectors instead of numbers.

A very nice feature of this program is that it works for ANY vector length.  If
the vector length is odd, it is only slightly faster than the regular DFT
program in the end of the directory.  If the length is even, it is slightly
faster, and the more factor of two, the faster.  If the length is a power of
two, the regular FFT algorithm is applied.

All this is in one algorithm, without discrimination of all cases!