From: John Dearden <john.dearden@...>
Date: 2007-08-25T08:25:54+09:00
Subject: Re: A simple question regarding ruby method argument

David A. Black wrote:
...stuff deleted...
> Since integers are immutable (luckily!), and local variables are
> local, you can't change an integer object via a reference copied to a
> method. If it helps, I can assure you that you would *not* want this
> to happen. It would be very weird if my local variables bindings were
> at the mercy of methods that I called.
> 
> What you're really looking for is an object container, and local
> variables don't really work that way. For container semantics you
> really need to use containers. You could do something like:

First, thanks for the quick answer.  That was unexpected.

Unfortunately I can't say I understand the part of your response I 
quoted above, other than that it says, "Nope, you can't do what you're 
trying to do.  Unless you're working with strings, which are somehow 
different."

The "local variables _bindings_" bit implies to me this has something to 
do with Ruby's underlying storage that I have not yet grasped.  I'm 
still thinking of a 'local variable' as really some chunk of memory, and 
the way the bits are set in that memory mean something in the context of 
my program.  If I pass that location to a subprogram, and know that it's 
going to put something else in it, that's good.

I can think of examples where I would like my subprogram to modify the 
local variables of the calling code.  For instance, I have two points, 
and I want to calculate m and b for the formula of a line, as in y = m * 
x + b.  I would be inclined to write a subprogram calc_m_b(x1, y1, x2, 
y2, var m, var b) (in Pascalese).  I could do what amounts to the same 
thing with two functions, one returning m and the other b, but that 
seems sort of silly in this case.  I could design an object that 
represented a line in some fashion, and let it hold m and b, but that's 
not always what you'd want, either.

Maybe I'm not thinking in terms of objects enough yet?

Thanks again,
John
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