final/test/utilities/function.objects/arithmetic.operations/transparent.pass.cpp

#include <functional>
#include <string>

template <class _Tp>
struct is_transparent
{
private:
    struct __two {char __lx; char __lxx;};
    template <class _Up> static __two __test(...);
    template <class _Up> static char __test(typename _Up::is_transparent* = 0);
public:
    static const bool value = sizeof(__test<_Tp>(0)) == 1;
};


int main () {
#if _LIBCPP_STD_VER > 11

    static_assert ( !is_transparent<std::plus<int>>::value, "" );
    static_assert ( !is_transparent<std::plus<std::string>>::value, "" );
    static_assert (  is_transparent<std::plus<void>>::value, "" );
    static_assert (  is_transparent<std::plus<>>::value, "" );

    static_assert ( !is_transparent<std::minus<int>>::value, "" );
    static_assert ( !is_transparent<std::minus<std::string>>::value, "" );
    static_assert (  is_transparent<std::minus<void>>::value, "" );
    static_assert (  is_transparent<std::minus<>>::value, "" );

    static_assert ( !is_transparent<std::multiplies<int>>::value, "" );
    static_assert ( !is_transparent<std::multiplies<std::string>>::value, "" );
    static_assert (  is_transparent<std::multiplies<void>>::value, "" );
    static_assert (  is_transparent<std::multiplies<>>::value, "" );

    static_assert ( !is_transparent<std::divides<int>>::value, "" );
    static_assert ( !is_transparent<std::divides<std::string>>::value, "" );
    static_assert (  is_transparent<std::divides<void>>::value, "" );
    static_assert (  is_transparent<std::divides<>>::value, "" );

    static_assert ( !is_transparent<std::modulus<int>>::value, "" );
    static_assert ( !is_transparent<std::modulus<std::string>>::value, "" );
    static_assert (  is_transparent<std::modulus<void>>::value, "" );
    static_assert (  is_transparent<std::modulus<>>::value, "" );

    static_assert ( !is_transparent<std::negate<int>>::value, "" );
    static_assert ( !is_transparent<std::negate<std::string>>::value, "" );
    static_assert (  is_transparent<std::negate<void>>::value, "" );
    static_assert (  is_transparent<std::negate<>>::value, "" );
    
#endif

    return 0;
    }