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From: David Abrahams (dave_at_[hidden])
Date: 2003-11-04 03:32:57

Eric Friedman <ebf_at_[hidden]> writes:

> David Abrahams wrote:
>> 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.
> Well, I didn't say the convention would work both ways. But anyway,
> after more thinking I see that the potential confusion resulting from
> my approach may easily outweigh the convenience of pretty syntax.
> The question now: what should we call variant< type-seq >?

Hm? If you're agreeing with me as you appear to be, it's just
variant< type-seq >.

> Ah, I didn't realize that the ... is actually part of the syntax and
> not just some way of conveying the semantics of the proposal.
> I *definitely* would like to see something like this in C++0x.

Give us a chance to get it working for function arguments first; the
class template argument case is the easy one.

Dave Abrahams
Boost Consulting

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