From: Austin Ziegler <austin@...>
Date: 2003-08-05T10:42:30+09:00
Subject: Re: clearing a parameter in Ruby?

On Tue, 5 Aug 2003 04:56:50 +0900, Roy Patrick Tan wrote:
> Austin Ziegler wrote:
>> Why do you wish to do this? We might be able to help you figure out a
>> better way to do what you're trying to do.
> In essence, what I'm trying to do is create a set of container classes
> that, when an object is inserted into a container, the container
> guarantees that the object does not change state until it is taken out
> again.

class ImmutablesArray < Array
  def push(it)
    it.freeze
    super
  end
end

Roughly. There's a few other methods you would want to implement (like #pop) 
to unfreeze as you pop the item, but this should work in general.

> The problem is that in Ruby (and almost all modern imperative languages)
> two variables can refer to the same object.

So can C++.

If you want objects in Ruby immutable, #freeze them.

> I guess your real question is, what kind of software am I building that
> requires these kind of components? I don't really need them, I was
> writing what was supposed to be a quick and dirty program when I realized
> how totally reliant I am on aliasing, and wondered how easy it would be
> to implement in Ruby some of the non-aliasing components I've been
> studying.

I'm not sure what you mean by "aliasing" here.

-austin
--
austin ziegler    * austin@halostatue.ca * Toronto, ON, Canada
software designer * pragmatic programmer * 2003.08.04
                                         * 21.38.17