Re: Fun python 3.2 one-liner

From	Giacomo Boffi <giacomo.boffi@polimi.it>
Newsgroups	comp.lang.python
Subject	Re: Fun python 3.2 one-liner
Date	2011-04-05 07:36 +0200
Organization	The Sun and The Rain
Message-ID	<86d3l1w96y.fsf@aiuole.stru.polimi.it> (permalink)
References	<df2af546-af99-4e69-bc8e-38c21a045a29@z27g2000prz.googlegroups.com> <o%pkp.365$0s5.220@newsfe17.iad> <86k4f9wzgx.fsf@aiuole.stru.polimi.it> <mailman.20.1301953602.9059.python-list@python.org>

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Chris Angelico <rosuav@gmail.com> writes:

>> def f(x,n,w): return x if n==1 else\
>>    (lambda x0=f(x[::2],n/2,w[::2]),\
>>            x1=f(x[1::2],n/2,w[::2]): reduce(lambda a,b: a+b ,\
>>                                      zip(*[(x0[k]+w[k]*x1[k],\
>>                                             x0[k]-w[k]*x1[k])\
>>                                             for k in range(n/2)])))()

> What sort of parameters does this take? So far all I can figure out
> is that n is an integer and x and w are sliceables, but I'm not sure
> whether x and w should be strings or arrays.

def direct_fft(x,n):
  return f(x,n,[exp(-2*pi*1j*k/n) for k in range(n/2)]) 
def inverse_fft(x,n):
  return [x/n for x in f(x,n,[exp(+2*pi*1j*k/n) for k in range(n/2)])] 
-- 
le mie sacrosante questioni di principio
          VS     gli sciocchi puntigli di quel cretino del mio vicino

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Re: Fun python 3.2 one-liner harrismh777 <harrismh777@charter.net> - 2011-03-29 14:00 -0500
  Re: Fun python 3.2 one-liner gb <gb@cabiate.it> - 2011-04-04 22:09 +0200
    Re: Fun python 3.2 one-liner Chris Angelico <rosuav@gmail.com> - 2011-04-05 07:46 +1000
      Re: Fun python 3.2 one-liner Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-04-05 10:16 +1200
        Re: Fun python 3.2 one-liner Chris Angelico <rosuav@gmail.com> - 2011-04-05 08:45 +1000
        Re: Fun python 3.2 one-liner Emile van Sebille <emile@fenx.com> - 2011-04-04 15:46 -0700
      Re: Fun python 3.2 one-liner Giacomo Boffi <giacomo.boffi@polimi.it> - 2011-04-05 07:36 +0200

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