From: "Daniel P. Zepeda" <daniel@...>
Date: 2003-01-30T13:34:15+09:00
Subject: Re: A simple program but strange output

On Thu, 30 Jan 2003 13:13:43 +0900
"Maggie  Xiao" <mxiao@ee.ualberta.ca> wrote:

> Hi there,
> 
> I wrote a simple program to enumerate an array. The code is as below:
> class Test
>  def initialize
>    @x=[0,1,2]
>    @tem=@x
>    @y=@x
>    y=del(@tem)
>  printf "#{@x}\n"
>  printf "#{@y}\n"
>           end
>   def del(x)
>  x.delete_at(0)
>  return x
>  end
> end
> a=Test.new
> 
> But the output is :
> 12
> 12
> Why  @x and @y are changed? Is there anyone can tell me how to deal with
> this problem?

Because @tem is a reference (pointer) to the object, which is the array
[0,1,2], and so is @y. @x,@y and @tem are all pointing to the same Array
object, they are not different objects. 
If you want different objects, you have to make a copy:

Here's an example using irb:

irb(main):001:0> a = [0,1,2]
=> [0, 1, 2]
irb(main):002:0> a.id
=> 537808534
irb(main):003:0> b = a
=> [0, 1, 2]
irb(main):004:0> b.id
=> 537808534
irb(main):005:0> c = a.clone
=> [0, 1, 2]
irb(main):006:0> c.id
=> 538070796
irb(main):007:0> 




> 


-- 
Daniel P. Zepeda