Re: Re: [Implementation] Calling wrapped functions, converters, policies

David Abrahams wrote:

> Daniel Wallin <[email protected]> writes:
> 
> 
>>>>Yeah, that would work fine. But I'm not sure I like it. How does it
>>>>apply to explicit conversions? (object_cast<> / extract<>). I had
>>>>thought that we'd handle these cases by just supplying a vector1<T>
>>>>signature sequence.. 
>>>
>>>    vector2<T,object>  // from-XXX
>>>or     vector2<object,T>  // to-XXX
>>>Simple ;-)
>>
>>So we would generate a dummy converter? Hackish. :)
> 
> 
> I guess.  You don't like it?

I don't really care that much, it's just an implementation detail. If it
works and gets us more uniformity that's fine by me.

> 
>>>>But we could tell the policy to generate the converter explicitly
>>>>instead of using generate_converter_tuple<>.. I'm not sure what I
>>>>think about this.
>>>
>>>Not sure what you're driving at here.
>>
>>We could invoke the nested apply<> explicitly instead of applying it
>>while iterating over a signature sequence.
>>
>>   template<class T, class ConverterGenerator>
>>   T extract(..., ConverterGenerator)
>>   {
>>       typename mpl::apply2<
>>           ConverterGenerator
>>         , T
>>         , mpl::int_<0>
>>       >::type cv;
>>
>>       return cv.convert(...);
>>   }
> 
> 
> I'm a little bit lost.  Not enough context.  Do I need to follow this?
> If so, can you make a new post about just this subject?

I don't think so. It might come up later, but I don't know. So lets
leave it for the time being.

> 
> 
>>>>Yeah I think we did. I guess most of "the others" will likely just
>>>>ignore the index though, provided that the index is passed to the
>>>>converter later.
>>>>
>>>>   struct my_cv;
>>>>   my_cv cv;
>>>>   cv.from(..., mpl::int<2>());
>>>>
>>>>vs
>>>>
>>>>   template<int N>
>>>>   struct my_cv;
>>>>   my_cv<2> cv;
>>>>   cv.from(...);
>>>
>>>Do we want to pass the index into the converter later?  I don't
>>>think we do.  Seems to me that you might want some converters to,
>>>ultimately, work on several indices.  Maybe I'm wrong.
>>
>>No I think you are right. It's a bit annoying to bind the index in
>>the converter type though. It does mean we could potentially be
>>subject to more code bloat since we are using compile time
>>indices.. But I don't know if there's a way around that, at least
>>not a good one.
> 
> 
> I don't seem to care much ;-) You can't plan for everything.  We can
> always rearchitect later.

Agreed.

-- 
Daniel Wallin



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