From: Michael 'entropie' Trommer <mictro@...>
Date: 2005-12-28T02:42:17+09:00
Subject: Re: Translate from Python to Ruby

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* Simon Kr?ger (SimonKroeger@gmx.de) wrote:
> Sorry, i couldn't resist:
>=20
> class Array
>   def powset
>     (0...(2**size)).map do |n|
>       (0...size).reject{|i|n[i].zero?}.map{|i|at(i)}
>     end
>   end
> end

lovely peace of code!
(it makes my brain burning but its nice!)
>=20
> cheers
>=20
> Simon
>=20
> Stefan Walk wrote:
>=20
> >Non-recursive version:
> >I'm sure you can translate this for sets...
> >
> >class Array
> >  def powset
> >    ret =3D []
> >    0.upto(2**size - 1) do |n|
> >      ret << []
> >      0.upto(size - 1) do |i|
> >        ret.last << self[i] if (n & (1 << i)) !=3D 0
> >      end
> >    end
> >    ret
> >  end
> >end
> >
> >p [].powset
> >p [1].powset
> >p [1,2].powset
> >p [1,2,3].powset
> >[[]]
> >[[], [1]]
> >[[], [1], [2], [1, 2]]
> >[[], [1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3]]
> >
> >
>=20
>=20
So long
--
Michael 'entropie' Trommer;  http://ackro.org

ruby -e "0.upto((a=3D'njduspAhnbjm/dpn').size-1){|x| a[x]-=3D1}; p 'mailto:=
'+a"

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