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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

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