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

[Arnaud Delobelle]

Derek Martin <code at pizzashack.org> writes:

> I think he meant None...  Or at least, I personally see a distinction
> between zero and None (and so do the Python docs).  Zero is a value,
> whereas None is specifically intended to denote the lack of any value.

None is an 'value' which is intended to denote the absence of any
'value' *other than None*.

> I would, FWIW, only make such a distinction in the context of a
> computer program...  Clearly in mathematics and elsewhere, zero is the
> lack of a value (it is the value of nothingness).

I would like to have a word with your maths teacher!  There are plenty
of uses for 0, most of which are unrelated to 'nothingess'.  E.g. 0 is
*greater* than -1 so it must be something.

-- 
Arnaud