SFINAE + sizeof = detect if expression compiles
- by FredOverflow
I just found out how to check if operator<< is provided for a type.
template<class T> T& lvalue_of_type();
template<class T> T rvalue_of_type();
template<class T>
struct is_printable
{
template<class U> static char test(char(*)[sizeof(
lvalue_of_type<std::ostream>() << rvalue_of_type<U>()
)]);
template<class U> static long test(...);
enum { value = 1 == sizeof test<T>(0) };
typedef boost::integral_constant<bool, value> type;
};
Is this trick well-known, or have I just won the metaprogramming Nobel prize? ;)
EDIT: I made the code simpler to understand and easier to adapt with two global function template declarations lvalue_of_type and rvalue_of_type.
