[Newbies] Re: squeak and the jvm

[Klaus D. Witzel]

On Wed, 08 Nov 2006 19:07:40 +0100, Michael Kohout wrote:

> Thanks Klaus.  So....does #become change the address of what 'after'
> points to,

Yes, and vice versa, simultaneously.

> so these two references now point to the same location in
> memory,

No, but there is a variant of #become: which can do that if needed.

> or does it clone what 'before' references and point 'after' to
> it?

No, there is no cloning (copying) involved, just a pointer swap whereever  
these two pointers appear in the .image (so in every object pointing to  
them).

> Or does it do something more complex?

No, it's just one of the two straight forward cases above.

/Klaus

> On 11/8/06, Klaus D. Witzel <klaus.witzel at cobss.com> wrote:
>> Hi Mike,
>>
>> on Wed, 08 Nov 2006 18:13:17 +0100, you wrote:
>> > Yes, this is what I was referring to.  Hotswapping is sort of there
>> > for the jvm.  When I use Eclipse, it tries to hotswap.  Sometimes it
>> > fails.  Sometimes it doesn't.  But, referring the criteria in my reply
>> > to Ron's email, would loosing guaranteed hotswapping cause Squeak to
>> > "lose it's soul?"  I dunnknow.  I'm a newbie.  And I don't write
>> > Squeak for a living.
>>
>> Having read your response to Ron's I think that all you ask for is to
>> compile Squeak source code into JVM bytecode such that your application
>> code can access the existing Java API's.
>>
>> Is this correct?
>>
>> If so, you'd need no hotswapping: your classes, inst vars and methods
>> don't change when your app runs in production mode.
>>
>> In my previous response I considered running *all* of the Squeak .image  
>> on
>> the JVM, that would be quite a difference and would rely on 100%[tm]
>> hotswapping (etc) being supported.
>>
>> > But in a Java environment I can tell you it isn't that bad.  And it's
>> > downsides could be mitigated so long as Squeak/JVM could provide some
>> > runtime mechanism to register some services to begin at startup(like
>> > Commanche, etc).  Maybe this would be a tolerable compromose to most
>> > Squeak developers if it provides more opportunities to use Squeak in
>> > the wider world and enlarges it's user base.
>> >
>> > But I don't have a clue about #become.  What does it do?
>>
>> It changes the object identity of receiver and argument regardless of
>> where they are referenced (in the Squeak .image), like in
>>   before := 'Klaus'.
>>   after := 'kwl'.
>>   before become: after.
>>   after printString "prints 'Klaus' "
>>
>> There are applications in Smalltalk/Squeak which depend on #become: for
>> example when growing an OrderedCollection.
>>
>> But if in such cases (like OrderedCollection) you'd always use a
>> corresponding Java class then, again, it wouldn't matter.
>>
>> I can say so because I have written a compiler for Smalltalk source code
>> into JVM bytecode, which works and can compile itself, but it's not  
>> ready
>> for prime time yet (and all the limitations of the JVM like #become: and
>> hotswapping, etc, apply).
>>
>> /Klaus
>>
>> > On 11/8/06, Klaus D. Witzel <klaus.witzel at cobss.com> wrote:
>> >> Hi Mike,
>> >>
>> >> if by "more message oriented opcode" you mean Gilad Bracha's
>> >> Invokedynamic
>> >> opcode
>> >>
>> >> - http://www.google.com/search?q=jvm+Invokedynamic
>> >>
>> >> this is not sufficient for full Smalltalk/Squeak. Though it may be
>> >> sufficient for scripting languages (languages in which, usually,  
>> types
>> >> are
>> >> unknown at compile-time).
>> >>
>> >> What is also needed is full "hotswapping"
>> >>
>> >> - http://blogs.sun.com/gbracha/entry/jsr292_and_hotswapping
>> >>
>> >> and support for Smalltalk's #become: ...
>> >>
>> >> But, perhaps, you had something else in mind?
>> >>
>> >> /Klaus
>> >>
>> >> On Wed, 08 Nov 2006 16:55:50 +0100, Michael Kohout wrote:
>> >>
>> >> > I suppose this is more of a pie in the sky type question, but with  
>> the
>> >> > changes coming to the Java virtual machine in version 7, where the  
>> jvm
>> >> > itself provides a more message oriented opcode, has any  
>> consideration
>> >> > gone into perhaps porting squeak to run on the jvm?
>> >> >
>> >> > I'm aware of talks2 but it seems as if development on that
>> >> > effort(based on the public releases/news) is at a standstill.
>> >> >
>> >> > thanks
>> >> > Mike Kohout
>> >>
>> >>
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>>
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