Official definition of call-by-value (Re: Finding the instance reference...)

Terry Reedy tjreedy at
Tue Nov 18 21:55:10 CET 2008

Steven D'Aprano wrote:
> On Sun, 16 Nov 2008 15:46:54 -0800, rurpy wrote:

> For example, consider the two electrons around a helium nucleus. They 
> have the same mass, the same speed, the same spin, the same electric 
> charge, the same magnetic moment, they even have the same location in 
> space (technically, the same wave function).

By quantum mechanics (Pauli Exclusion principle), this is impossible.

 > They are identical in every
> possible way. Are they the same electron, or two different electrons? 
> What does the question even mean?

That you do not understand QM?

Photons, on the other hand, can be identical, hence lasars.

Matter is divided into leptons and bosons, individualists and 
communalists.  (I believe I have the name right.)

>> For example, you can define the value of None however you want, but it
>> seems clear that it has (and needs) no intrinsic-value.
> To me, that seems just as silly as arguing that zero is not a number,

To me, that distortion of his (and my) point is silly.  0 partipipates 
in numerous integer operations, whereas None participates in no NoneType 
operations.  (Neither has attributes.)  And that is the difference he is 
pointing at.

> or that white pixels are "nothing" and black pixels are "something".

This is a ridiculous attempt at ridicule;-)  Pixels have positions and 1 
to 4 graded attributes.  Completely different from None.


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