From: Robert Klemme <shortcutter@...>
Date: 2011-03-24T17:05:26+09:00
Subject: Re: iteration question

On Thu, Mar 24, 2011 at 2:20 AM, bbiker <renard@nc.rr.com> wrote:
> On Mar 23, 7:20 pm, Rimantas Liubertas <riman...@gmail.com> wrote:
>> data = Array.new(5,[])
>> This gives you array with five references to the same array object:
>>
>> ruby-1.9.2-p0 :036 > data = Array.new(5,[])
>> => [[], [], [], [], []]
>>
>> ruby-1.9.2-p0 :037 > data[0].object_id
>> => 2156232780
>> ruby-1.9.2-p0 :038 > data[1].object_id
>> => 2156232780
>>
>> > 0.upto(4) do |i|
>> > data[i].push(i)
>>
>> no matter where you push you are still pushing to the same single array
>>
>> What you want probably is:
>>
>> data = Array.new(5) {[]}
>> 0.upto(4) do |i|
>> data[i].push(i)
>> end
>> p data
>>
>> In this case it is the same as
>>
>> data = Array.new(5) {|index| [index]}
>> => [[0], [1], [2], [3], [4]]
>>
>> Regards,
>> Rimantas
>> --http://rimantas.com/
>
> Alternate way of doing the same thing:
>
> data = []
> 0.upto(4) { |i| data << [i] }

Even simpler

irb(main):001:0> data = Array.new(5) {|i| [i]}
=> [[0], [1], [2], [3], [4]]
irb(main):002:0> data = Array.new(5) {|*a| a}
=> [[0], [1], [2], [3], [4]]
irb(main):003:0> data = 5.times.map {|i| [i]}
=> [[0], [1], [2], [3], [4]]

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/