From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-08-01T04:19:49+09:00
Subject: Re: How to Emulate C/C++ Pointer/Reference in Ruby?

Well, probably for the temporary variable it is not very useful to have a
"reference to a", but for an object attribute it may make more sense.

Because I am in the middle of playing around with Ruby C API, do you think
it will be beneficial to create my own type of class of reference?  It may
be something like this.

cReference = rb_define_class ("Reference", rb_cObject);

static VALUE
reference_init (VALUE self, VALUE obj, char* name)
{
    rb_iv_set (self, "@obj", obj);
    rb_iv_set (self, "@name", name);
    return self;
}

reference_read (VALUE self)
{
    return rb_iv_get (rb_iv_get (self, "@obj"), STR2CSTR (rb_iv_get (self,
"@name")));
}

rb_define_method (cReference, "initialize", reference_init, 2);
rb_define_method (cReference, "value", reference_read, 0);

(I don't like the last line.  For lvalue, I think the method name is
simply "="; but what is the method name for rvalue?)

Yes, this is in priciple the same as creating the accessor function in
Ruby, but won't it be useful in general?  Or I guess so far nobody needs a
general-purpose reference/pointer class in Ruby.

Regards,

Bill
===========================================================================
David Alan Black <dblack@candle.superlink.net> wrote:
> [My understanding, subject to corrective intervention]

> The thing is that in Ruby, every variable holds a reference to some
> object, and variables are all at the same level of remove from their
> objects.  (This is probably wrong or different for immutables, but I'm
> excluding them for the moment.)  So if you have:

>   a = [1,2,3]

> there's no way to get a "reference to a", the way you can have
> "pointer to pointer [to pointer [...]]" in C.  What you *can* have is
> other references to the same object:

>   b = a

> So in Ruby, rather than the infinitely regressing line of pointer
> relationships, you get something more like a circle of references, all
> equidistant from the object and all terminal (in the sense that
> they're at the furthest possible level away from the object).


> David

> -- 
> David Alan Black
> home: dblack@candle.superlink.net
> work: blackdav@shu.edu
> Web:  http://pirate.shu.edu/~blackdav