From: Mark Wilson <mwilson13@...>
Date: 2003-08-05T06:03:10+09:00
Subject: Re: clearing a parameter in Ruby?


On Monday, August 4, 2003, at 03:56 PM, Roy Patrick Tan wrote:

> [snip]

> 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.

This sounds a little like a tuple.
See http://sourceforge.net/project/showfiles.php?group_id=50485
which includes an implementation of a tuple class (a container that is 
ordered and immutable).

The code, which is not very long, is at the bottom of this page:

http://www.rubygarden.org/ruby?AdditionalSetMethods


> The problem is that in Ruby (and almost all modern imperative 
> languages) two variables can refer to the same object. So part of the 
> solution is never to use assignment except when creating an object (if 
> you need a copy of an object, clone it). But that still leaves us w 
> parameter passing, since a variable in the caller environment refers 
> to an object that is also referred to by a variable in the called 
> method... so I wanted to be able to clear the caller's variable.

I don't understand the problem here. Why are the variables important as 
long as you are passing the object around? Every value in Ruby is also 
an object -- even if it's assigned to a variable within a class, an 
instance of a class or a method.

I still don't understand what you want your program to do.

> [snip]