From: Rolf Pedersen <rolfhsp@...>
Date: 2010-04-25T07:03:04+09:00
Subject: Re: Metaprogramming - Array initialization

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Agree with Joel.  Use the block form of the new method, or you'll get
multiple references to the same object.
This piece of code I believe does the trick. (No fault handling included,
and probably not the most elegant, perhaps since I'm quite new to Ruby.)

def make_array(*a)
  a.flatten!
  if a.size > 1
    Array.new(a.shift){make_array(a)}
  elsif a.size == 1
    Array.new(a.shift)
  end
end

irb(main):052:0> make_array(1, 3, 2, 1)
=> [[[[nil], [nil]], [[nil], [nil]], [[nil], [nil]]]]

Best regards,
Rolf


On Sat, Apr 24, 2010 at 11:48 PM, Joel VanderWerf
<joelvanderwerf@gmail.com>wrote:

> Paul A. wrote:
>
>> Hi,
>>
>> In Ruby, we can declare array as explain in the doc:
>> http://ruby-doc.org/core/classes/Array.html#M002150
>>
>> That makes possible many kind of use, such as:
>>
>>> Array.new(1, Array.new(3, Array.new(2, Array.new(1))))
>>>>
>>> => [[[[nil], [nil]], [[nil], [nil]], [[nil], [nil]]]]
>>
>> For my needs, I would like to use a code that declare an array of any
>> arrays that we want. I don't know if it is possible.
>>
>
> The above is probably not what you want. Look:
>
> >> a=Array.new(3, Array.new(2))
> => [[nil, nil], [nil, nil], [nil, nil]]
> >> a[0][1] = 6
> => 6
> >> a
> => [[nil, 6], [nil, 6], [nil, 6]]
>
> Try using the block form:
>
> >> a=Array.new(3) {Array.new(2)}
> => [[nil, nil], [nil, nil], [nil, nil]]
> >> a[0][1] = 6
> => 6
> >> a
> => [[nil, 6], [nil, nil], [nil, nil]]
>
>

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