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POOne-liner Algorithm to Combine Arrays into Arrays of All Possible Value Combinations?
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  1. POOne-liner Algorithm to Combine Arrays into Arrays of All Possible Value Combinations?
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    copied!<p>Not quite sure I have the question fully formed, but what I'm trying to do is basically this:</p> <pre><code># where the indices correspond to attributes fore example: # [type, status] x = %w(a b) y = %w(c d) combine(x, y) #=&gt; [["a", "b"], ["a", "d"], ["c", "a"], ["c", "b"]] </code></pre> <p>The order of the array is always the same, so the reverse of each, such as <code>[b, a]</code>, are not included in the result.</p> <p>What is this called and what's an efficient way to implement this?</p> <p>I see <a href="http://www.ruby-doc.org/core/classes/Array.html#M000288" rel="nofollow">Array#permutation</a>, but that's not quite it...</p> <p>This would hopefully work for any number of arrays and values: <code>combine(*arrays)</code></p> <p>Thanks!</p> <p><strong>Update</strong></p> <p>Here's a better example of what I'm looking for:</p> <p>This <code>(x | y).combination(x.length).to_a</code> produces the following:</p> <pre><code>x = ["front_door", "open"] y = ["back_door", "closed"] (x | y).combination(x.length).to_a =&gt; [["front_door", "open"], ["front_door", "back_door"], ["front_door", "closed"], ["open", "back_door"], ["open", "closed"], ["back_door", "closed"]] </code></pre> <p>The actual result I'm looking for is this:</p> <pre><code>=&gt; [["front_door", "open"], ["front_door", "closed"], ["back_door", "open"], ["back_door", "closed"]] </code></pre> <p>Or if it were a longer array:</p> <pre><code>x = ["house", "front_door", "open"] y = ["building", "back_door", "closed"] compute(x, y) =&gt; ["house", "front_door", "open"], ["house", "back_door", "open"], ["house", "front_door", "closed"], ["house", "back_door", "closed"], ["building", "front_door", "open"], ["building", "back_door", "open"], ["building", "front_door", "closed"], ["building", "back_door", "closed"] </code></pre> <p>Any ideas?</p>
 

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