How can I detect whether a type is a visible base of another type?

Question

If I do

struct A{};
struct C:private A{};

typedef char (&yes)[1];
typedef char (&no)[2];

template 
struct Host
{
 operato         


        

Answer 1

Do you have access to a compiler with C++11 support?

If so, you can combine Chad's use of static_cast with decltype to create a very simple type trait implementation (as demonstrated in this question). As per Jonathan Wakely's suggestion, the references have been replaced with pointers to avoid false positives when D defines an operator B&().

template struct AnyReturn { typedef void type; };

template
struct is_base_of: std::false_type {};

template
struct is_base_of( std::declval() ) ) >::type
>: std::true_type {};

When using gcc 4.7:

struct Base {};
struct PublicDerived  : public  Base {};
struct PrivateDerived : private Base {};

int main()
{
    std::cout << is_base_of::value << std::endl; // prints 1
    std::cout << is_base_of::value << std::endl; // prints 0
    return 0;
}