From: James Edward Gray II <james@...>
Date: 2007-07-10T21:44:23+09:00
Subject: Re: Repacking an array of arrays

On Jul 10, 2007, at 7:26 AM, dblack@wobblini.net wrote:

> Hi --
>
> On Tue, 10 Jul 2007, Robert Klemme wrote:
>
>> 2007/7/10, Kaps Lok <jocubeit@gmail.com>:
>>> 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.
>>
>> Try this:
>>
>> require 'enumerator'
>> p [[1, 4, 7, 10, 13], [2, 5, 8, 11, 14], [3, 6, 9, 12,
>> 15]].flatten.to_enum(:each_slice, 3).to_a
>
> And in 1.9 I guess it would be:
>
> array.flatten.each_slice(3).to_a
>
> I'd like to see a method (I don't think there is one) in 1.9 that
> would return the sliced-up array without the need for the explict to_a
> operation.  I suspect the most common use will be exactly that.

I bet rolling �_with_index iterators will be pretty common too:

   enum.each_with_index.inject�


James Edward Gray II