is_composite.h

 
//          Copyright John McFarlane 2018.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file ../LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
 
#if !defined(CNL_IMPL_NUM_TRAITS_IS_COMPOSITE_H)
#define CNL_IMPL_NUM_TRAITS_IS_COMPOSITE_H
 
#include <type_traits>
 
namespace cnl {
    template<class T>
    struct is_composite : std::false_type {
        static_assert(!std::is_const<T>::value, "T is const");
        static_assert(!std::is_volatile<T>::value, "T is volatile");
    };
 
    template<class T>
    constexpr auto is_composite_v = is_composite<T>::value;
 
    namespace _impl {
        // cnl::_impl::are_composite
 
        template<class... Args>
        struct are_composite;
 
        template<>
        struct are_composite<> : std::false_type {
        };
 
        template<class ArgHead, class... ArgTail>
        struct are_composite<ArgHead, ArgTail...>
            : std::integral_constant<
                      bool, is_composite<typename std::decay<ArgHead>::type>::value
                                    || are_composite<ArgTail...>::value> {
        };
    }
}
 
#endif  // CNL_IMPL_NUM_TRAITS_IS_COMPOSITE_H