From: Robert Dober <robert.dober@...>
Date: 2007-01-27T16:51:51+09:00
Subject: Re: pass by reference?

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On 1/27/07, dblack@wobblini.net <dblack@wobblini.net> wrote:
>
> Hi --
>
> On Sat, 27 Jan 2007, Martin C. Martin wrote:
>
> >
> >
> > Phrogz wrote:
> >> If you pass an immutable type by reference, does it make a sound?
> >> Er, I mean...
> >> If you passed an immutable type by reference, how would you know that
> >> it wasn't passed by value?
> >
> > Is there any way for the function you're calling to modify the value of
> the
> > variable in the caller?  Pass by reference can do that.
>
> You can modify the object to which the variable refers:
>
>    def change_me(obj)
>      obj << "hi"
>    end
>
>    arr = [1,2,3]
>    change_me(arr)
>    p arr          # [1, 2, 3, "hi"]
>
> In this example, arr contains a reference to an array.  In change_me,
> obj contains another copy of the same reference, so you can use it to
> manipulate and change the original array.
>
> I still wouldn't call this pass by reference (see my earlier post in
> this thread).


Just to demonstrate your point

def modifying a_param
    a_param = "hi"
end

a_value = "low"

modifying a_value
case a_value
when "hi"
    puts "Passed by reference"
when "low"
   puts "Passed by value"
else
   puts "Passed away"
end

or to put it different
x = a.object_id
method a
a.object_id == x  # for sure

Robert

David
>
> --
> Q. What is THE Ruby book for Rails developers?
> A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
>     (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
> Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
> A. Ruby Power and Light, LLC (http://www.rubypal.com)
>
>


-- 
"The best way to predict the future is to invent it."
- Alan Kay

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