Overriding return type in function template specialization

Question

I would like to specialize a function template such that the return type changes depending on the type of the template argument.

class ReturnTypeSpecializati         


        

Answer 1

Perhaps you could use the following hack. Given these simple type traits:

template
struct conditional { typedef T type; };

template
struct conditional { typedef U type; };

template
struct is_same { static const bool value = false; };

template
struct is_same { static const bool value = true; };

You could write your class and specialized member function as follows:

class ReturnTypeSpecialization
{
public:
    template
    typename conditional::value, int, T>::type 
    Item();
};

// Normally just return the template type
template
typename conditional::value, int, T>::type
ReturnTypeSpecialization::Item() { return T(); }

// When a float is specified, return an int
template<>
int ReturnTypeSpecialization::Item() { return 1.0f; }

Simple test program (uses C++11 just for verification):

int main()
{
    ReturnTypeSpecialization obj;
    static_assert(std::is_same()), bool>::value, "!");
    static_assert(std::is_same()), int>::value, "!");
}

Here is a live example.