Finding the instance reference of an object

[Lie]

On Nov 4, 9:33 am, Joe Strout <j... at strout.net> wrote:
> On Nov 3, 2008, at 5:27 PM, Marc 'BlackJack' Rintsch wrote:
>
> > Maybe this is a surprise for you, because we haven't discussed this in
> > much detail in this group lately, but it applies to Python which does
> > call-by-object or call-by-sharing.  ;-)
>
> There's no such thing.  Those are just terms made up by the Python  
> community to in place of the more standard "call-by-value" terminology  
> to make Python seem more mysterious than it really is.  I guess you  
> can call it "purple bananas" if you want, but the behavior is exactly  
> the same as what every other language calls call-by-value.
>
> But I really am trying not to continue this debate.  So that's my last  
> reply about it for tonight, I promise.  :)
>
> Cheers,
> - Joe
> <http://www.strout.net/info/coding/valref/>

I'm fed up with you.

In Von Neumann Architecture computers, only pass-by-value is natively
supported. Other idioms are made on top of pass-by-value.

That's why exclusively pass-by-value languages like C is most flexible
than other exclusively pass-by-<insertanythinghere>.

BUT the difference is clear, if you want to do pass-by-reference in C
(I prefer to call it faux pass-by-reference), you'd have to manually
find a variable's address, pass it by-value, then dereference the
address. Compare with VB's ByRef or C++'s &, which does all that
_automatically_ for you behind the scene.

Another example: pass-by-object. I disagree with the term pass-by-
object-reference, since the notion of object reference is unnecessary
in a true pass-by-object mechanism (i.e. we should travel outside VNA
realm for a true pass-by-object mechanism). Problem is: I'm not aware
of any computer architecture that can accommodate pass-by-object
natively or whether such architecture is feasible to be made.
Solution: Emulate such architecture on a VNA computer. Limitations:
pass-by-object implementation on a VNA computer requires the notion of
object reference/pointer because VNA computers cannot pass object, it
can only pass numbers.

In pass-by-object, the whole object is passed around, not a copy of
the object like in pass-by-value or a copy of the pointer to the
object like in faux pass-by-reference. This makes pass-by-object
actually closer to pass-by-reference than to pass-by-value, since the
notion of VNA's requirement for Object Reference means passing
pointers around. But don't let it confuse you, the pass-by-object
mechanism itself does not recognize Object Reference, unlike pass-by-
reference recognition of reference/pointer.

Now that I have clearly defined the line between pass-by-object and
pass-by-value, I'm left with you thinking what's the difference
between pass-by-object and pass-by-reference. In pass-by-reference,
names are _mnemonic to location in memory_. In pass-by-object, names
are _mnemonic to objects_. In pass-by-reference, when we assign a
value to the name, we'd assign a value _to the location in memory_. In
pass-by-object, when we assign a value to the name, we assign an
object _to the name_. When passing parameters, pass-by-reference
systems passed the memory address and alias that memory address to a
local name. In pass-by-object system, since the object itself has no
idea of its own name, so it is rebound to a local name. You can say
that pass-by-reference system is memory-location-centered, while pass-
by-object system is name-centered.

To summarize, the key bit you're missing is built-in _automatic_
abstraction from pass-by-value. All pass-by-<insertanything> except
pass-by-value is an emulation over an architecture that can only
natively pass-by-value. pass-by-reference is emulated in C, C++, and
VB by passing memory address/pointer but C isn't a by-ref system
because C doesn't provide the automatization. What makes python's
parameter passing called as pass-by-object is because python provides
the automatization to make it seems that you can do true pass-by-
object.