Re: [C++-sig] [Implementation] Calling wrapped functions, converters, policies

Daniel Wallin <[email protected]> writes:

> At 12:47 2003-09-21, David Abrahams wrote:
>>Daniel Wallin <[email protected]> writes:
>>
>> > Does the converter really need access to the whole argument list? I
>> > don't see why, at least if we do the "filtering" before passing it
>> > into the converter function. I thought this is what you are doing in
>> > Boost.Python with the new changes, but I could have misunderstood.
>>
>>Yes, that's what I'm doing, but it's not ideal.  For example, what
>>gets passed to converters for out arguments that don't actually even
>>appear in the XXX arguments?  What if you want a converter to combine
>>two XXX arguments to produce one C++ argument?  These are the sorts of
>>things that are possible with SWIG typemaps but not with Boost.Python.
>
> Ok, that's kind of cool. So what you are suggesting is that the converter
> gets the entire argument package, and the index?
>
>    c0.convert(argument_package, mpl::int_<1>());

Actually I was thinking that the index should be encoded in the type
of the converter.

>> >>Anything I'm missing?  Your thoughts?
>> >
>> > No I think that about covers it. The current implementation (in
>> > luabind, and some of langbinding..) doesn't use tag-dispatching for
>> > the invoke functions, but I guess there are reasons that
>> > tag-dispatch is better than class specialization here.
>> >
>> > BTW, does Boost.Python handle const functions/objects?
>>
>>There's no notion of const objects in Python, so although we do
>>"handle" const member functions and objects, we don't do anything
>>special for them.  There is a notion of immutability which applies to
>>*types* (not objects), and I've thought about how that could be
>>handled: http://mail.python.org/pipermail/c++-sig/2002-May/001023.html
>>but haven't implemented anything.
>>
>> > In luabind we do
>>
>>What precisely do you mean by that?
>
> I mean we preserve constness in the objects that are held in lua. We have
> a bool in our object_rep that tells us if the object is const or not. This is
> used in overload resolution.

Whoo hoo!  Well, I'll be happy to take that feature; we should just
put it in langbinding ;->

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com



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