From: Shannon Fang <xrfang@...>
Date: 2002-11-28T16:09:20+09:00
Subject: Re: call-by-reference problem again

Hi Bill,
In my test the Arrays are all pointing to the same object, but the
strings are not. I now understand that david has explained what happed
in my prog.

tks.
shannon

On Thu, 28 Nov 2002 08:15:18 +0900
William Djaja Tjokroaminata <billtj@y.glue.umd.edu> wrote:

> Shannon Fang <xrfang@hotmail.com> wrote:
> > Another problem about reference is that,
> > if a is an object, let b=a, then b is a copy of the object or a pointer
> > to a? I encountered the following problem
> 
> > a=b=c=Array.new
> > d=e=f=""
> 
> > In my program, if I modify a, b and c will be affected, in another word,
> > a, b, c point to the same Array. while I modify d, e and f are not
> > affected, which means, strings are assigned by value... what will happen
> > if I write d=e=f=String.new?
> 
> > Since everything in Ruby is object, I don't understand why String and
> > Array are different...
> 
> > Shannon
> 
> Hi Shannon,
> 
> I don't think your statement above is right.  In Ruby, if you have
> 
>    a = b = c = ... = anything   # Array.new, or "", or String.new, or else
> 
> then if you call a "!" method on any of the above variables, then all the
> variables are "affected" because in essence, there is only one single
> object, which is referred to by so many variables.
> 
> So using your own terminology/concept, in b=a, then b is a copy of the
> "pointer" to a, and not a copy of the object pointed to by a.  Please see
> also http://www.glue.umd.edu/~billtj/ruby.html#objects.
> 
> Regards,
> 
> Bill