[C++-sig] Re: Custom WeakPtrs and "None"
Stefan Haller
haller at ableton.com
Fri Nov 19 16:48:15 CET 2004
David Abrahams <dave at boost-consulting.com> wrote:
> haller at ableton.com (Stefan Haller) writes:
>
> > Yes, I don't want the Python variable itself to be set to None
> > literally, I know there's no way to do that. I just want it to *look* a
> > bit more like None if the WeakPtr is NULL. For example, I was hoping
> > that it is possible to play tricks with overloading __cmp__ (or some
> > such) to make the expression (weakptr == None) evaluate to True if
> > weakptr is not None, but its pointee is NULL.
>
> You could play that trick manually. I would definitely *not* want to
> do that automatically in the library.
Could you please give me a hint how I would go about that? I'm afraid I
don't know what exactly has to be done.
> Note that if you wrap this function:
>
> X* identity(X* x) { return x; }
>
> you actually *will* get None back if you pass it one of these
> released weak_ptrs.
Yes, this is to be expected, right? But I'm not sure how I can make use
of this in solving my problem.
--
Stefan Haller
Ableton
http://www.ableton.com/
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