Kenny Riddile wrote:
I'm trying to create a type trait to detect the presence of a constructor with a very specific signature. Types passed to this trait will *always* have a constructor of the form:
T( const std::string& );
but some of them will have this constructor as well:
T( const std::string&, Foo& ); // Second parameter will always be a Foo&
I would like to create a type trait that returns true when the second constructor is present. I can't simply do:
!is_convertible<std::string, T>::value
since that will return false when the second constructor is present since all Ts are convertible from std::string. Is it possible to create such a trait?
As Steven Watanabe noted, "AFAIK, it's impossible." These sound like very specific constructors that you're looking for, however, so it might be reasonable to use a "flag typedef" within the class (intrusive) and/or an explicitly specialized metafunction (non-intrusive)...? - Jeff