the use of #pointsTo: (Re: Boolean expressions (was: Re: [squeak-dev] Re: Object>>#is:? (was: Re: PackageDependencyTest)))

On 4 March 2010 23:23, Bert Freudenberg <[hidden email]> wrote:
Yeah. Just a guess, we can add #identityIncludes: to Array
which will use same primitive as pointsTo:

Btw, i find it surprising that:

Array new pointsTo: Array

answering false.

An instance of class is always points to its class, no?

But its great, since we can use this 'bug/feature' to implement
#identityIncludes:  :)

> - Bert -
>


--
Best regards,
Igor Stasenko AKA sig.

Hi Igor,

On Thu, Mar 4, 2010 at 10:43 PM, Igor Stasenko <[hidden email]> wrote:
> Btw, i find it surprising that:
>
> Array new pointsTo: Array
>
> answering false.
>
> An instance of class is always points to its class, no?

doesn't #pointsTo: only take indexable / named fields into account?
The class is encoded in the header, that might well be out of scope.
Also, Array is a special class (fast lookup from 1-word header),
right? So the pointer is even less easy to extract. :-P

I need to go to sleep now. :-)

Best,

Michael

On 4 March 2010 23:47, Michael Haupt <[hidden email]> wrote:
Well, but when you walking the object graph (and #pointsTo: is
existing exactly for doing that), you need to know all connections
without exceptions.
This is where #pointsTo: lies to us, because obviously, all instances
pointing to their corresponding classes.
Concerning subtleties, like special header format and things like
that: hey, this is a primitive after all, and it quite easy to
get a class object from its instance. Otherwise , how then a message
sending machinery might work without being able to do that? :)

> Best,
>
> Michael
>
>



--
Best regards,
Igor Stasenko AKA sig.

On Thu, Mar 04, 2010 at 11:43:22PM +0200, Igor Stasenko wrote:
>
> Btw, i find it surprising that:
>
> Array new pointsTo: Array
>
> answering false.
>
> An instance of class is always points to its class, no?

  (Array with: Array) pointsTo: Array ==> true

The "points to" refers to the object pointers in the indexable fields
of an object.

Dave