On Saturday, 8 September 2012 at 23:58:36 UTC, Walter Bright
wrote:
On 9/8/2012 3:56 PM, Mehrdad wrote:
I was pretty excited to figure out that a one-liner FFT is
possible in D!
creal[] dft(creal[] v) { return v.length > 1 ? (p =>
chain(map!(q
=> q[0] + q[1])(p), map!(q => q[0] -
q[1])(p)))(zip(dft(v.stride(2).array()), map!(p => p[1] *
expi(p[0] * -2 * PI / v.length))(zip(iota(v.length / 2),
dft(v.drop(1).stride(2).array()))))).array() : v; }
Of course, the Python version is still shorter:
def dft(v): return (lambda e, o: map(add, e, o) + map(sub, e,
o))(dft(v[0::2]), [o * rect(1, k * -2 * pi / len(v)) for k, o
in
enumerate(dft(v[1::2]))]) if len(v) > 1 else v
but it's still cool (barring the unreadability, haha).
Yay D!
Awesome! Thanks for figuring this out. Any chance you can write
up a brief article on this, so we can post a link on reddit?
Haha... I wish, but I don't have a blog or anything like that.
Currently I'm working on schoolwork though so I'm not sure I'd
get to this in time. :\
If someone else wants to do it though, feel free to!
Also, obligatory mention, sorry I didn't mention this earlier --
Bearophile is right on, I got the original code from
http://rosettacode.org/wiki/FFT (Python) and then I played around
with it to make it a one-liner.
Credits go there for the original code, not me. :)
