I have a template-class and wrote a operator- which should do the math with 2 objects of different type and return it as a new object. Now i'm wondering how can i declare this operator- in my class, since something like
template<typename S>
friend auto operator-(const XY<T>,const XY<S>)->XY<decltype(T-S)>;
isn't allowed? Here is my example code:
template <typename T>
class XY{
private:
T x
...
// template<typename S>
// friend auto operator-(const XY<T>, const XY<S>)->XY<decltype(T-S)>;
};
template <typename T, typename S>
auto operator-(const XY<T> z1, const XY<S> z2)->XY<decltype(z1.x - z2.x)>{
decltype(z1.x - z2.x) x;
x = (z1.x - z2.x);
XY<decltype(x)> n(x);
return n;
}
Is this what you are looking for?
template <typename T>
class XY{
private:
T x;
template <typename U, typename S>
friend auto operator-(const XY<U> z1, const XY<S> z2)->XY<decltype(z1.x - z2.x)>;
};
template <typename T, typename S>
auto operator-(const XY<T> z1, const XY<S> z2)->XY<decltype(z1.x - z2.x)>{...}
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