[Newbies] true/false defined where?
sean at monkeysnatchbanana.com
Tue Aug 5 15:20:46 UTC 2008
On Aug 5, 2008, at 10:52 AM, Randal L. Schwartz wrote:
>>>>>> "Sean" == Sean Allen <sean at monkeysnatchbanana.com> writes:
> Sean> I have a feeling the secret to unraveling that confusion comes
> from this:
> Sean> 'true and false and some of the very few objects known to the
> Sean> does that mean that I can't go and find these variables
> anywhere? that
> Sean> they arent true global variables they are some sort of special
> If you explore "Smalltalk specialObjectsArray", you'll see a special
> list of
> variables that both the VM and the Smalltalk code have to agree on
> in order to
> run. For example, if a primitive wants to return "false", it has to
> know what the rest of the Smalltalk image considers the sole instance
> of the "False" class.
> These items are established in
> "SystemDictionary>>#recreateSpecialObjectsArray", the first version
> of which
> had to be executed essentially "by hand" on the first VM (either the
> versions of Smalltalk 76 or 80). Since then, this special array has
> its initial values by running it in an already running system, so
> the first
> few entries there (nil, false, true) are in fact clones of clones of
> clones of
> the original handcrafted objects. Of course, there's code on the VM
> side that
> knows the precise order of this magical array, and this is what
> allows them to
> communicate, so you can't just add new things here or change the
> without building a corresponding new VM.
Thanks for the pointer of where to explore and the background info.
In a couple days when I've had time to review and digest hopefully it
will all make sense.
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