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Subject: Re: [boost] [MPL][vector] Is there interest in mpl::vector using variadic templates?
From: paul (pfultz2_at_[hidden])
Date: 2017-03-02 20:55:12

On Wed, 2017-03-01 at 21:56 +0300, Antony Polukhin via Boost wrote:
> 2017-02-21 13:52 GMT+03:00 Михаил Максимов via Boost <
> >
> > Dear community,
> >
> > I've recently started contributing to boost::variant. To speed up
> > variant's
> > compilation I'm implementing mpl::vector on variadic templates. For
> > now
> > status of new vector implementation is:
> <...>
> >
> > made me wonder, is there interest in variadic templates
> > implementation? Are
> > there limitations for it's usefulness, which I did not see?
> I'm very interested in patching MPL to be able to use variadic
> templates.
> There are many C++ libraries and code that use MPL. Those libraries
> can not switch from MPL to Metal or Hana because:
> * they have to be usable in C++98/C++03 and C++11
> * they have a huge code base that can not be simply migrated to new
> library
> * they depend on third party libraries that use MPL and need the
> ability to interact with those libraries
> Moreover, making MPL variadic will not just speed up compilation, but
> also will:
> * reduce executable size and improve startup times if MPL structure
> is
> part of an exported entity
> * improve runtime speed if MPL structure is part of an entity that is
> used in operations involving typeid()
> So please, continue the work and make a pull request.

I wonder if instead an MPL implementation could be written with a Metal
backend for newer compilers and use the legacy MPL for C++03 compiler.
I thought Bruno was developing something like that at one point. So
building off of that could be useful. Although, Metal is not in boost
yet, hopefully it will be soon.


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