Re: [boost] New dependency report

El 07/06/2014 17:37, Vicente J. Botet Escriba escribió:

...

To be standard conforming, we would need to add "std::integral_constant" as "type" member. But IMHO this seems a bit redundant.

Well, currently something more

template struct integral_constant {

static constexpr T value = v; typedef T value_type; typedef integral_constant type; constexpr operator value_type() const { return value; } constexpr value_type operator()() const { return value; }

};

Vicente C++ International Standard

Yes. The issue is not about deriving from integral_constant if it's a very simple header with no dependencies. Currently if deriving from integral_constant: 1) We need to depend on another Boost library (type_traits and its dependencies, boost::integral_constant derives from mpl::integral_c so we start adding dependencies) 2) In C++11 compilers we need to choose between boost::integral_constant or std::integral_constant. A standard conforming trait is not convertible to boost::true_type. On the other hand: static const bool value = true/false seems very lightweight and portable. An alternative is to inject std::integral_constant into the boost namespace or derive boost::integral_constant from std::integral_constant if it adds more operations. If integral_constant is needed to define a simple trait, then integral_constant should be: - compatible with C++11. - extremely simple, without any further dependencies, and live in core (not in type_traits, mpl or any other library). Just my 2 cents, Ion