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Hi All,<br>
IMO, every object has three essential properties: Identity, State, and
Behavior. In Smalltalk, State and Behavior are defined by the object's
flattened class hierarchy. The Object ID is not explicitly available. I
have am using 'asOop', hoping I get a unique value. But I realize that
I am skating on thin ice because its comment confuses me with
implementation details. It doesn't say what it means by 'pointer', so
there is still hope:<br>
<br>
<i>Object>>asOop<br>
"Primitive. Answer a SmallInteger whose value is half of the
receiver's <br>
object pointer (interpreting object pointers as 16-bit signed
quantities)..."</i><br>
<br>
<i>ProtoObject>>identityHash<br>
"Answer a SmallInteger whose value is related to the receiver's
identity..."<br>
</i>This is pretty vague, but the term 'Hash' indicates that many
objects can share the same value. So it is clearly cannot be used as
the objectID.<br>
<br>
The Morph>>printOn: implementation is less than ideal because it
should apply to all objects, not only Morphs. Also, it should use
'asOop' rather than 'identityHash' to let us hope for uniqueness.<br>
<br>
In short:<br>
<ul>
<li>Smalltalk claims to be object oriented and I regard it as a
serious flaw that the object ID is not explicitly visible.</li>
<li>We probably need a 64-bit VM to represent it properly, e.g.,
using the standardized definition of OID, but a value that is
guaranteed to be unique within the current set of objects would be
acceptable..</li>
<li>I regard it as a bug that Object>>printOn: does not present
some kind of object ID. </li>
</ul>
Cheers<br>
--Trygve<br>
<br>
<br>
On 2009.08.20 06:37, K. K. Subramaniam wrote:
<blockquote cite="mid:200908201007.18504.subbukk@gmail.com" type="cite">
<pre wrap="">On Wednesday 19 Aug 2009 11:07:29 am Ronald Spengler wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Ah, so the GC in the VM swizzles the pointers out from under you.
<a class="moz-txt-link-freetext" href="http://lists.squeakfoundation.org/pipermail/squeak-dev/1999-June/006170.htm">http://lists.squeakfoundation.org/pipermail/squeak-dev/1999-June/006170.htm</a>
l
</pre>
</blockquote>
<pre wrap=""><!---->This is the classic dilemma between name as an identifier and name as a
locator. The word "pointer" connotes the latter but gets used widely in the
former sense in Smalltalk code. Object Identifier (oid) is unambiguous but
doesn't sound half as cool as oop ;-).
Subbu
</pre>
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<p class="MsoNormal" style=""><span class="SpellE"><span
style="font-size: 10pt; font-family: Arial;" lang="EN-GB">Trygve</span></span><span
style="font-size: 10pt; font-family: Arial;" lang="EN-GB">
Reenskaug<span style=""> </span>mailto: <span class="SpellE"><a class="moz-txt-link-abbreviated" href="mailto:trygver@ifi.uio.no">trygver@ifi.uio.no</a></span></span><span
style="font-size: 10pt; font-family: Arial;"><o:p></o:p></span></p>
<p class="MsoNormal" style=""><span class="SpellE"><span class="GramE"><span
style="font-size: 10pt; font-family: Arial;" lang="EN-GB">Morgedalsvn</span></span></span><span
class="GramE"><span style="font-size: 10pt; font-family: Arial;"
lang="EN-GB">.</span></span><span
style="font-size: 10pt; font-family: Arial;" lang="EN-GB"> 5A <span
style=""> </span><a class="moz-txt-link-freetext" href="http://heim.ifi.uio.no/~trygver">http://heim.ifi.uio.no/~trygver</a><o:p></o:p></span></p>
<p class="MsoNormal" style=""><span
style="font-size: 10pt; font-family: Arial;">N-0378
Oslo<span style=""> </span>Tel: (+47) 22 49 57 27<o:p></o:p></span></p>
<p class="MsoNormal" style=""><span class="SpellE"><span
style="font-size: 10pt; font-family: Arial;">Norway</span></span><span
style="font-size: 10pt; font-family: Arial;"><o:p></o:p></span></p>
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