Re: [boost] New dependency report

Subject: Re: [boost] New dependency report
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-06-06 14:40:04

On Friday 06 June 2014 16:39:13 John Maddock wrote:
> > 
> > MPL decomposition is also pending, but it's probably better to split it
> > into two modules MPL and MPL.Core, similar to TypeTraits. For many cases
> > dependency on MPL.Core would be enough.
> 
> I'm tied of saying this.... but if mpl::bool_ and int_ were moved out of
> MPL full, either to core, or to some mpl_core, then there's no need to
> split type_traits anymore.

Yes, that's one way to do it. However, TypeTraits.Core could have no 
dependency on MPL at all an be sufficient for things like value_init.hpp and 
blank.hpp. Arguably this way has more potential.

> Indeed I suspect there's a huge amount of obfuscated code inherited from
> mpl's broken-compiler-workarounds that can now be removed: not only do
> we not support those compilers any more, but given that they haven't
> been tested in heaven knows how long they're unlikely to compile *any*
> of modern Boost anyway.
> 
> In fact in C++11 it makes sense to me have:
> 
> namespace boost{ namespace mpl{
> 
> template <bool b>
> using bool_ = std::integral_constant<bool, b>;
> template <int i>
> using int_ = std::integral_constant<int, i>;
> 
> }
> 
> // replaces boost::integral_constant:
> using std::integral_constant;
> 
> }
> 
> Now any function or template that's overloaded/specialized on mpl::bool_
> or int_ will also "just work" with std:: type_traits as well as boost ones.

Yes, that's something to consider when working on MPL.Core.