Type trait to check that all types in a parameter pack are copy constructible

Question

I need a type trait to check whether all types in a parameter pack are copy constructible. This is what I\'ve done so far. The main function contains some test cases, to che

Answer 1

If the inheritance from std::true_type or std::false_type is not important, then this can be done in straightforward way without SFINAE:

template 
struct areCopyConstructible;

template<>
struct areCopyConstructible<> : std::true_type {};

template 
struct areCopyConstructible {
    static constexpr bool value = std::is_copy_constructible::value
        && areCopyConstructible::value;
};

If you want to inherit from std::true_type or std::false_type, you can use std::conditional:

template 
struct areCopyConstructible;

template<>
struct areCopyConstructible<> : std::true_type {};

template 
struct areCopyConstructible : 
    std::conditional::value,
        areCopyConstructible,
        std::false_type
    >::type
{};