[SOLVED] C++ Setup own cast rules for template classes/structures

C++ Setup own cast rules for template classes/structures

is it possible to implement your own cast rules and to make the compiler give a warning about it rather than an error?

I'm currently working with SFML (doesn't really matter if you don't know it) and it has a simple Vector2 structure like this:

template <typename T>
struct Vector2 {
    Vector2<T>(T,T);
    T x,y;
}

Now I'm using this quite often and would like to setup a custom cast rule for this structure, since I can't modify the source code. I currently have a function that needs a Vector2<int>, but a function I use returns a Vector2<unsigned int> and the compiler doesn't seem to be able to cast the one into the other which is a bit weird.

I know I can use the casts (and static_cast works), but it seems a bit too elaborate for a a simple conversion like this, and a bit stupid that I can't test my program because of this. So what I'm probably searching for are compiler commands that can setup such cast rules.

Solution

There are two ways to do this (both ways require you to modify the definition of Vector2). You can add a non-explicit constructor that performs the conversion:

template <typename T>
struct Vector2 {
    template<typename U>
    Vector2(Vector2<U> const& u) : x(u.x), y(u.y){}
    Vector2(T x,T y) : x(x), y(y) {}
    T x,y;
};

or you can add a non-explicit type-cast operator:

template <typename T>
struct Vector2 {
    template<typename U>
    operator Vector2<U>(){
        return Vector2<U>(x,y);
    }
    Vector2(T x,T y) : x(x), y(y) {}
    T x,y;
};