[Vm-dev] Compact class question

Gabriel Hernán Barbuto gbarbuto at gmail.com
Tue Dec 7 11:43:48 UTC 2010

On Tue, Dec 7, 2010 at 11:30 AM, Yoshiki Ohshima <yoshiki at vpri.org> wrote:
> At Tue, 7 Dec 2010 10:53:12 +0100,
> Gabriel Hernán Barbuto wrote:
>> Hi Yoshiki
>> Maybe I have not made myself clear about which expression my comment
>> referred to. Read my mail again, but I will copy it here again:
>> headerWords :=
>>        contentsWords > 63
>>                ifTrue: [3]
>>                ifFalse: [(cl indexIfCompact > 0) ifTrue: [1] ifFalse: [2]].
>> Replacing the 63 for a 62 will make the trick and besides if
>> contentsWords is greater than 62 it should be greater than or equal to
>> 63. So what you propose is the same. But be careful that it's not in
>> totalWords expression.
>> I think this object should have a 3-word header. What do you think about this?
>  Yes, I think so.
>  I didn't quite understand the intent of original question ("Is it
> fine to have an instance of compact class that doesn't have a one word
> header?").  The answer, as Bert wrote, an object needs to have the
> base header, if the "one word header" refers to the base header.

My question was if it is possible to have an instance of a compact
class with a 3-word header. I thought that all compact classes
instances should have only a 1-word header. I understand that the base
header will always be there. But I was not sure if it was legal to
have more than the base header for compact classes instances.

Hope this makes my question clearer.


>> With respect to what we are doing. We are porting MicroSqueak to
>> Pharo. MicroSqueak could be useful for teaching. The next step(we are
>> also working in parallel on this) is to build kernel images but
>> different from MicroSqueak. In order to do that, we need to remove all
>> the bad dependencies on the kernel classes and clean up the Pharo
>> image.
>> What are you doing with MicroSqueak?
>  Cool, and thank you.  In some ways, what we are doing is similar; we
> wrote an app in Squeak but trying to understand what other parts of
> Squeak the app is using and going from bottom up sounds like an
> intersting idea.
> -- Yoshiki

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