From: "Jörg W Mittag" <JoergWMittag+Ruby@...>
Date: 2010-09-15T00:15:09+09:00
Subject: Re: Iterate over a cartesian product.

Handy Gandy wrote:
> I have an array of N arrays A_i: [A_1,A_2,...,A_N].
> 
> I want to iterate over the cartesian product A_1xA_2...xA_N.
> 
> Is there a simple way of doing this without specifying N?

    ary = [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
    ary.first.product(*ary.drop(1))
    # => [
    # =>   [1, 3, 6], [1, 3, 7], [1, 3, 8], [1, 3, 9], 
    # =>   [1, 4, 6], [1, 4, 7], [1, 4, 8], [1, 4, 9], 
    # =>   [1, 5, 6], [1, 5, 7], [1, 5, 8], [1, 5, 9], 
    # =>   [2, 3, 6], [2, 3, 7], [2, 3, 8], [2, 3, 9], 
    # =>   [2, 4, 6], [2, 4, 7], [2, 4, 8], [2, 4, 9], 
    # =>   [2, 5, 6], [2, 5, 7], [2, 5, 8], [2, 5, 9]
    # => ]

jwm