Re: [Boost-Users] No more than 10 types in boost::tuple?

From: Jaakko Jarvi (jajarvi_at_[hidden])
Date: 2003-05-30 13:41:26

The current Boost::tuple implementation is limited to 10 arguments.
As you pointed out, one can use cons lists directly to circumvent this
limitation. Tuples are now part of the C++ standard techical report,
meaning that they are likely to be part of the next standard library
revision. The interface of the std::tr1::tuples do not include
the cons list part, as there are other viable implementation options for
tuples. We have written (together with Joel Guzmann) a preprocessor based
implementations of tuples, which will allow up to 50 (I think, or even
more) element tuples. That implementation will find its way to boost in
some schedule, hopefully to the next release. It'll likely coexist with
the current implementation, at least for some time to come.

  Cheers, Jaakko

--
-- Jaakko Järvi                       email: jajarvi_at_[hidden]
-- Post Doctoral Fellow               phone: [phone]
-- Pervasive Technology Labs          fax:   [phone]
-- Indiana University, Bloomington
On Fri, 30 May 2003, Tarjei Knapstad wrote:
> On Fri, 2003-05-30 at 14:08, Tarjei Knapstad wrote:
> > I tried constructing a tuple with 12 types today without much luck.
> I've
> > read through the headers to see if there was any obvious way of
> getting
> > around the 10 limit but couldn't find one (I half expected to find
> > something along the way of vectorxx<>, in MPL).
> >
> > Am I being stupid, or is there really no way of constructing a tuple
> > with more than 10 elements?
> >
> It just occured to me that I can make the 10th template argument of
> tuple a "cons" list in itself, but I find this a bit awkward, i.e.
>
> typedef cons<float, cons<int, cons<double, null_type> > >  some_types;
> typedef tuple<type1, type2, ..., some_types>   large_tuple;
>
> Should tuple by default allow for more than 10 types? Or at least
> provide macros ala Alexandrescu's typelist construction macros?
>
>
> Cheers,
> --
> Tarjei
>
>
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