Re: [boost] [config][mpl][type_traits][integer] BOOST_STATIC_CONSTANT should use constexpr

Le 21/04/13 17:45, John Maddock a écrit :

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I'm not against this radical alternative, and I even like it. I don't know which compilers need the enum workaround and if Boost should support them.

The list seems to be:

VC7 and earlier Vacpp 5.02 and earlier (currently 11.1) Sunpro 5.6 and earlier. MPW all versions?

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What I want is just that integral_constant use them so that all the traits in Boost conforms to the C++11 standard.

Out of curiosity, can you detect the difference? What can you do with constexpr values that you can't with static const ones?

Even if most of the uses of integral_constant is to use its member ::value integral constant defines also the operator(), so it is a nullary functor. integral_constant a; constexpr int f(); template <int I> void g(); template <typename F> void h(F&& fct) { g(); } h(&f); h(a); The last sentence will not compile if the operator() is not a constexpr and it can not be a constexpr if ::value is not a consexpr, or can it? As you can see the case is not current, but who know what the user want to do with boost::integral_constant. The status quo means that it can not do the same thing that with std::integral_constant. Note that the operator() has just been proposed for C++14, but there is however the conversion operator to the value type. Best, Vicente