From: karoyakani <tj.takei@...>
Date: 2007-01-29T14:45:05+09:00
Subject: Re: cartesian product of arrays

How about recursive version?

module Enumerable
  def cartprod(*args)
    return self if [] == args
    b = args.shift
    result = []
    self.each do |n|
      b.cartprod(*args).each do |a|
        result << [n] + (a.kind_of?(Array)? a: [a])
      end
    end
    result
  end
end

def cartprod(*args)
  args.shift.cartprod(args)
end

Then both forms work as below:
p (1..2).cartprod((3..5), (6..8))
p cartprod([1,2],[3,4,5],[6,7,8])

Further consideration would be to use a block for output formating:
e.g. replace result << [n] + a above to yield n, a and a block {|n,a| n
+a.join(' ')} for string concatination etc

FYI,
TJ


On Jan 27, 10:14 am, Peter Szinek <p...@rubyrailways.com> wrote:
> Thomas Hafner wrote:
> > Peter Szinek <p...@rubyrailways.com> wrote/schrieb <45B9E90C.7010...@rubyrailways.com>:
>
> >> Just a suggestion: it is also possible to reopen Enumerable and put your
> >> code there - in this case, all enumerable types will have this
> >> functionality (e.g. Sets), not only Arrays.
>
> > Does that follow your suggestion?:Exactly!
>
> Cheers,
> Peter
>
> __http://www.rubyrailways.com