From: "David A. Black" <dblack@...>
Date: 2005-10-03T05:51:14+09:00
Subject: Re: C++ equivs in Ruby

Hi --

On Mon, 3 Oct 2005, Robert Klemme wrote:

> Pascal GUICHARD <pascal.guichard@gmail.com> wrote:
>
>> - on pointers, i try to understand (howto implement) datastructures
>> in which you need to mix values and references/poiters
>
> You cannot use values in Ruby directly.  There are only references.  Think of 
> Ruby as Java without POD's.  In practice there are some optimizations for 
> Fixnums, Symbols and some other types but conceptually (i.e. from a usage 
> point of view) you never see values directly.
>
> x = nil
> x = Object.new
> x = "foo"
> x = 123
>
> Here "x" is always a reference variable - like every other variable is a 
> reference variable.  It's so simple but sometimes difficult to get used to - 
> especially when coming from other programming languages.

I think the "immediate value" status of Fixnums etc. goes beyond just
being an optimization, though, and has some practical consequences and
even some explanatory power.  In particular, in:

   x = 123

x holds the immediate value 123, rather than a reference to it, which
is the rationale Matz has always given for not having x++ (i.e., it
would be equivalent to doing 123++ and that would make no sense).


David

-- 
David A. Black
dblack@wobblini.net