sample of has_mem_xxx.

has_mem_xxx.cpp

// sample of has_mem_xxx.
// this can be compiled with MS VC2012.

#include <iostream>
#include <utility>
#include <type_traits>

template< typename T >
struct has_mem_xxx {
    template< typename U > static std::true_type check( decltype( std::declval<U>().xxx )* );
    template< typename U > static std::false_type check( ... );
	static const bool value = std::identity<decltype(check<T>(nullptr))>::type::value;
};

struct A
{
	int xxx;
};

struct B
{
	int yyy;
};

using namespace std;

int main()
{
	cout << has_mem_xxx<A>::value << endl;
	cout << has_mem_xxx<B>::value << endl;
	return 0;
}