From: dblack@...
Date: 2007-07-10T12:11:14+09:00
Subject: Re: Repacking an array of arrays

Hi --

On Tue, 10 Jul 2007, Kaps Lok wrote:

> Is there an elegant (maybe a one-liner) for repacking:
>
> [[1, 4, 7, 10, 13], [2, 5, 8, 11, 14], [3, 6, 9, 12, 15]]
>
> to?
>
> [[1, 4, 7], [10, 13, 2], [5, 8, 11], [14, 3, 6], [9, 12, 15]]
>
> So rather than having 3 arrays each with 5 elements, I get five arrays
> of 3 elements each...
>
> the only way I can see to do this is by looping the array, and creating
> new arrays.

If you have ActiveSupport you can do:

   array.flatten.in_groups_of(3)

with the caveat about flatten that it flattens greedily.  If you
don't, you can easily get it or roll your own in_groups_of.  (It was
one of the first things I ever wrote for myself in Ruby, though I
think I called it in_slices_of or something.)


David

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