C++ static operator overloading

问题:

Is it possible to overload C++ class operators in the static context? e.g.

class Class_1{ ... }
int main()
{

    Class_1[val]...

}

回答1:

If you are looking for metaprogramming using the built-in operator: Such a thing isn't possible - the built-in operators operate on runtime values, not on compile time values.

You may use boost::mpl for that, and instead of using the built-in operators, use its templates, like at for op[], plus<a, b> for op+ etc.

int main() {
    using boost::mpl::vector;
    using boost::mpl::at_c;
    using boost::mpl::plus;
    using boost::mpl::int_;

    typedef vector<int, bool, char, float> Class_1;
    typedef vector< int_<1>, int_<2> > Numeric_1;

    at_c<Class_1, 0>::type six = 6;
    typedef plus<at_c<Numeric_1, 0>::type 
                ,at_c<Numeric_1, 1>::type>::type r;
    int i3[r::value] = { 4, 5, 6 };
    return ((i3[0] + i3[1] + i3[2]) * six) == 90;
}

回答2:

I don't believe it's possible, though I could be wrong on this front. I'd like to ask why you'd want to do this though. Rather than performing operations on a class instead of instances, perhaps you just require one instance throughout your application? In this case, you should probably be using the singleton pattern.

回答3:

If you mean the operator operates on a class, the No. That does not make sense, it is like saying operator + may operator on int or double. Operators are syntactic sugar for functions and they operate on varibles(values) not types.

回答4:

No, operators cannot be static members of a class. Use a regular static function instead.