From: gabriele renzi <surrender_it@...1.vip.ukl.yahoo.com>
Date: 2004-02-10T05:14:58+09:00
Subject: Re: Newbiest ? ever

il Tue, 10 Feb 2004 02:56:28 +0900, "Orion Hunter"
<orion2480@hotmail.com> ha scritto::

>(ruby 1.8.0 Linux)
>
>I don't understand why I get the following behavriour:
>
>irb(main):001:0> matrix = Array.new( 3, Array.new( 4, 0 ) )
>=> [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
>irb(main):002:0> matrix[0][0] = 1
>=> 1
>irb(main):003:0> matrix
>=> [[1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0]]
>irb(main):004:0>
>
>I would have expected the assignment of matrix[0][0] to produce a matrix:
>[[1,0,0,0],[0,0,0,0][0,0,0,0]]
>
>What am I not getting here?

Array.new(num,object) just creates num refernces to object:
irb(main):001:0> a=Array.new(3,'yo')
=> ["yo", "yo", "yo"]
irb(main):002:0> a[0].id
=> 20896272
irb(main):003:0> a[1].id
=> 20896272

what you want is different object with the same value, you can do this
with:
irb(main):004:0> a=Array.new(3) {'yo'}
=> ["yo", "yo", "yo"]
irb(main):005:0> a[0].id
=> 20863668
irb(main):006:0> a[1].id
=> 20863656

so you should write:

matrix= Array.new(3) do
 Array.new(4,0)
end

or just do:
require 'matrix'
:)