From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-11-27T02:27:07+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (11/24/02)

Jason Persampieri <helgaorg@yahoo.com> wrote:
> OK... I get it... I understood your argument (although
> ya cleared up a few other things), but I still just
> didn't GET why you couldn't do a '++' method that
> simply did something like 'self = self.succ'

Hi Jason,

Let me try to clear things up.  *Theoretically*, it is not impossible to
be able to write in some non-standard Ruby

    x = 5
    y = 5
    x.succ!    # -> x == 6, y == 5

in which case x and y actually have different id's.  This can be
accomplised if *all* objects/variables had simply been implemented as
VALUE which is a pointer.  I think this is done in some other languages
such as Tcl and Python.

However, *practically* we cannot do it in the current Ruby C
implementation, because [Fixnum, Symbol, true, false, nil] have been
implemented as VALUE which is an immediate object.  (Each object
is a "singleton" if you want to call it that way.)  I guess Matz created
the "immediate objects" for efficiency reason, but this has the
consequence of the impossibility to have x.succ! if x is a Fixnum.

Ruby is not 100% efficiency (something like C) and neither 100% consitency
(something like Smalltalk).  I think it is really a careful balance
between the two.

Regarding assignments of type 'self = something', you cannot do it in
Ruby, but for objects which are not immediate, at least in theory you can
do it if you use the Ruby C API's.

Regards,

Bill

P.S. I don't know what happens in the Java implementation of Ruby (JRuby),
whether it distinguishes between VALUE as pointer and as immediate object,
as Java does not have pointers in the C sense.