From: SpringFlowers AutumnMoon <summercoolness@...>
Date: 2007-09-30T09:09:36+09:00
Subject: Re: a = Dog.new # a is not a pointer and not a reference?

Austin Ziegler wrote:
> 
> A variable in Ruby isn't like Java, PHP, C++, C, or even Pascal.

Doesn't a Ruby variable behave the same way in Java, PHP5, C++, and 
Python?

As long as I view Ruby as a pointer to an object, everything clicks.

Except until it is the C++  int &i = a  or PHP's  int $a =& $b
then things start to get weird.. they call it reference...

and it behaves like this:

<?php

class Dog {
    var $name;

    function Dog($i) {
        $this->name = "I'm $i!\n";
    }
}

$a = new Dog("lulu");   # a is a reference to "lulu" object
$c = $a;                # c is a reference to "lulu" object
$b = &$a;               # b is a reference to reference ?
$b = new Dog("woofy");

echo "This is PHP ", phpversion(), "\n\n";

print_r($a);
print_r($b);
print_r($c);

?>

C:\rails\depot>php assign2.php
This is PHP 5.2.4

Dog Object
(
    [name] => I'm woofy!

)
Dog Object
(
    [name] => I'm woofy!

)
Dog Object
(
    [name] => I'm lulu!

)

First of all, we don't have things like $b =& $a in Ruby, right?  So in 
Ruby, we are very simple and clear.

Second, the PHP code above, $b is a reference (to reference), you see 
when you change $b, you are changing the thing it is referring to.  In 
this case, changing where $a is referring to.  There is no way you just 
ask $b to refer some where else unless you use the unset() function.

Maybe in Ruby, a = Dog.new("lulu")  we call a as a reference... then we 
can't really let "a" reference another object like using  a = 
Dog.new("woofy").  However, if you don't say a is a reference, but a 
"contains" a reference, then it might be possible...  then you can let a 
contain a different reference.

I think in Ruby, if we say "a" is a pointer, i can understand that.  if 
we say "a" is a reference, then i can't understand it, as a reference in 
the computer science field is that you can't change where it points to 
or refers to.  you always have to change the object where it refers to. 
but if you say "a" contains a reference... then i think that's fine, 
because "a" can contain a reference but it can contain another 
reference, and it is pointing else where.

somehow, i think calling int &i = a in C++ or $a =& $b in PHP as 
reference is somewhat confusing, as people tend to think reference 
meaning a pointer beforehand.  If we call int& i = a in C++ and $a =& $b 
just alias, then things are more clear.  Put it this way, if those 
things are called alias, then will we say in Ruby, a = Dog.new("lulu") 
as an "alias" to the object lulu?  or will we call a "a reference" to 
the object lulu.


-- 
Posted via http://www.ruby-forum.com/.