[boost] Re: Variant size bug?

From: David Abrahams (dave_at_[hidden])
Date: 2003-11-03 21:42:57

Eric Friedman <ebf_at_[hidden]> writes:

>> Interesting idea.  But in the end, types should be types should be
>> types.  I don't want types with special properties having unique
>> behavior when used as template parameters.  That would eventually
>> break all generic metaprogramming.
>
> I think that may be a bit extreme. Type sequences seem to me a rather
> unique exception...

       mpl::size<mpl::vector<int,long> >::type
       == mpl::size<int,long>::type

??

You can't go around making exceptions in the type system lightly.

>> Consider the syntax currently being discussed by the committee for
>> doing the same sort of thing with tuple types at runtime:
>>       f(some-tuple...)
>>       == f(at<0>(some-tuple), at<1>(some-tuple), ... )
>> That would lead to:
>>      F<type-seq...>
>>      == F< type-seq[0], type-seq[1], ... >
>> I rather like that symmetry.
>
> Wait, so does this mean you agree or disagree with me? I'm confused.

I agree strongly that it's a useful capability and disagree strongly
that it should happen without a special syntax (in this case "...").

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