Guido van Rossum wrote:
> On 4/21/06, Ron Adam <[EMAIL PROTECTED]> wrote:
>> Recently I found a case where I wanted to return something that was more
>> literally *nothing* than a None is. So maybe a null symbol of some sort
>> might be useful in other cases as well?
>
> You're not gonna get something that's a valid expression *and* is more
> "nothing" than None.
Yes, it would require special casing either by object methods and/or by
the interpreter to work in a general way. Which is probably enough of a
reason not to do it.
> On a case by case basis there might be syntax indicating the absence
> of something that is distinguishable from 'None'; for example, using
> *args you can reliaby whether an argument was passed or not (unlike
> using None as a default, which can be defeated by passing an explicit
> None).
Yes, in cases where containers are used, as in *args, the identity "x ==
x + empty_container" works. What I was looking for was the same
identity operations with an append method.
x == x.append(foo(y)) # when foo returns a NULL object.
Not that it's a big deal, I just thought it might also fit with Gregs
suggestion as well where a keyword with a NULL could indicate a defualt
isn't present and must be supplied when used as a defualt.
> But a generic NULL won't be part of the language.
I'm fine with that. I realized it may need a lot more *good* use cases
to not have the special isn't special enough guide line apply.
Cheers,
Ron
> --
> --Guido van Rossum (home page: http://www.python.org/~guido/)
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