On second thought, that seems weird. Maybe this is just a C background
talking, but why call a thing 'pointer' without being able to dereference
it?
 - Silly Ron, the Newbie

On Tue, Aug 18, 2009 at 9:41 PM, Ronald Spengler <ron.spengler at gmail.com>wrote:

> Familiar with hashes. Grok it; I can use it to see if two objects are the
> same object or not, and looking for a particular object by it's hash is
> probably expensive.
> Thank you:)
>
>
> On Tue, Aug 18, 2009 at 9:38 PM, Michael van der Gulik <mikevdg at gmail.com>wrote:
>
>>
>>
>> On Wed, Aug 19, 2009 at 4:19 PM, Ronald Spengler <ron.spengler at gmail.com>wrote:
>>
>>> When I (for example,) in a workspace, Command-P the text 'morph3874
>>> color: Color red' and see 'aMorph(2413)', what does the number mean? I'm
>>> guessing it's some kind of object pointer. An OOP perhaps, I've heard people
>>> speak of those? This has been bugging me for a year, and I can't seem to
>>> construct a Google string that finds me an answer to the question. Can I use
>>> that number to find the object in the object memory?
>>> Why I ask:
>>>
>>> I'm presently trying to understand...
>>>
>>> http://bugs.squeak.org/bug_view_page.php?bug_id=456
>>>
>>>
>> Look at the code in Morph>>printOn:
>>
>> Morph>>printOn: aStream
>>     | aName |
>>     super printOn: aStream.
>>     (aName := self knownName) notNil
>>         ifTrue: [aStream nextPutAll: '<' , aName , '>'].
>>     aStream nextPutAll: '('.
>>     aStream
>>         print: self identityHash;
>>         nextPutAll: ')'
>>
>> This gets called when you do alt-p on a morph in a workspace. The
>> second-to-last line is of interest; this is the number that you're seeing.
>> It's an "identityHash". I'm not going to explain hashing here; Wikipedia can
>> teach you more if you're curious.
>>
>> If you look at the implementation of ProtoObject>>identityHash, it is
>> primitive 75. If you look at the implementation of Object>>asOop, it is also
>> primitive 75. So, coincidentally, yes, it is an OOP (object pointer).
>>
>> The intention however was just to print out a number that is unique for
>> each different instance so that you can see whether two variables are
>> pointing to the same morph. This is useful for debugging. In my own images,
>> I often modify printOn: methods to print out hashes or oops for the same
>> reason.
>>
>> I'm not sure how you'd convert an oop to an object. I guess you could
>> search through all objects in the image looking for the right one.
>>
>> Gulik.
>>
>> --
>> http://gulik.pbwiki.com/
>>
>>
>>
>>
>
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