Fun python 3.2 one-liner

Giacomo Boffi giacomo.boffi at polimi.it
Tue Apr 5 07:36:53 CEST 2011


Chris Angelico <rosuav at 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)])] 
-- 
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