From: Phil Meier <phil.meier@...>
Date: 2007-09-18T16:15:04+09:00
Subject: Re: The meaning of  a = b  in object oriented languages

Lloyd Linklater schrieb:
> SpringFlowers AutumnMoon wrote:
>> Is that the case: if a is an object, then b = a is only copying the
>> reference?
> 
> That and it adds a counter.

I do not see the evidence of a counter.

> a = ["foo", "bar"]

that means, a points to the array object (with two elements).

> b = a

Now b also points to the same array object as a.

> b[0] = "bite me"

Element 1 (with index 0) get's changed - and since a and b both point to 
this array object, the changes are seen by both variables (a and b).

> p a, b
> 
> a = "different"

Now - a points to another object (of type string) then b. That the whole 
magic, i.e. no magic at all and no counter needed.

> p a, b
> 
> ***
> 
> In the first print, we get
> ["something else", "bar"]
> ["something else", "bar"]
> 
> showing that changing b changes a, as expected.  However, if we change 
> a, b is NOT changed as seen in the second print.

b is NOT changed because we did not change b and we also did not change 
the array object b points to.

> 
> "different"
> ["something else", "bar"]
> 
> That means that there is a counter inside that says to separate the two 
> or b would have changed with a as a changed with b initially.

This is not true. There is no need of any counter.

BR Phil