One-Way Become

On Dolphin 6, I evaluate this in a workspace:

   |  a b  |
    a := Time now.
    12345 timesRepeat: [Time now] .
    b := Time now.
    a oneWayBecome:    b.
    a =  b

-> true

But, according to the method-documentation of #oneWayBecome:

   " .... anObject replaces  all uses of the receiver, and the
     receiver's identity and  contents are lost.
   "

So you would expect the 'a' in my expression to become
nil, right?  Somehow it seems to 'lose' nothing in the
above example.  Is there a discrepancy between the
documentation and behavior? If so, which one should
be fixed?

Thanks for putting in the #oneWayBecome:.
I'd just like to be sure about its intended, stable,  semantics.

-Panu Viljamaa

Panu,

Hmmm... I don't understand what you're saying. For e.g.

|  a b  |
a := Time now. "12:45am"
12345 timesRepeat: [Time now]. "Is this just a delay?"
b := Time now. "12:46am"
a oneWayBecome:    b.
a =  b "true"
a == b "true"
a "12:46am"
b "12:46am"

So the original contenst of a (12:45am) were thrown away and GC'd and
replaced by the contents of b (12:46am). Now a and b point to the same
object.

Perhaps the comment should say "and the receiver's original identiity
and contents are lost".

Does that help?

--
Best regards,

Andy Bower
Dolphin Support
www.object-arts.com

Andy Bower wrote:
> ...
> So the original contenst of a (12:45am) were thrown away and GC'd and
> replaced by the contents of b (12:46am). Now a and b point to the same
> object.
>
> Perhaps the comment should say "and the receiver's original identiity
> and contents are lost".
>
> Does that help?

Yes, I now understand the source of my confusion. When
I first saw this  method I was quite excited that Dolphin
has more than one type of #become:.  So I immediately
thought "How can I create a test that shows this behavior?".

Your example shows that the two variables now point to
the same object, but it doesn't really show that one
object has "lost its identity". In fact there's no way
we  can show it has "lost its identity", because - it
no longer exists! And, it would be quite hard to devise
a test that shows it doesn't exist too. Your explanation
in terms of GC makes its much clearer, I think.

When the comment says "... receiver's identity and contents
are lost", it's a bit misleading because it's not the
receiver's content that is lost, it is the old contents
of the *variable* that previously held the receiver that
is now lost. The receiver (object) is 'lost', not the
'contents' of the receiver (object). #become:, as probably
everyone  agrees, must be the most subtle, yet at the same
time the most enlightening feature of Smalltalk.


Thanks
-Panu Viljamaa