Question

I was on codepad and I was trying to build up my skills using C++. I’d never used templates much before, so I tried looking into how to use them. The code below is the result, and unfortunately, it does not work. I did try to search for solutions to my problem, but since I don’t have much experience using templates, I couldn’t make any connections between my problem and other problems. So, I decided to ask for help.

template <class A>
class Vector2 {
public:
    A x,y;
    Vector2(A xp, A yp){
        this->x = xp;
        this->y = yp;
    }
};

template <class B, class A>
class rayToCast {
public:
    rayToCast(B angle, Vector2<A> origin, Vector2<A> point1, Vector2<A> point2){
        this->RAngle = angle;
        this->Point1 = point1;
        this->Point2 = point2;
    }
private:
    B RAngle;
    Vector2<A> point1,point2;
};

int main(){
    rayToCast<short int, float> ray(45, Vector2<float>(0.0, 0.0), Vector2<float>(-10.0, -3.0), Vector2<float>(5.0, 7.0));
    return 0;
}

Here’s the output:

t.cpp: In constructor 'rayToCast<B, A>::rayToCast(B, Vector2<A>, Vector2<A>, Vector2<A>) [with B = short int, A = float]':
t.cpp:26:   instantiated from here
Line 14: error: no matching function for call to 'Vector2<float>::Vector2()'
compilation terminated due to -Wfatal-errors.

Any help is appreciated.

Answer 1

The rayToCast constructor tries to initialize point1 and point2 by calling Vector2‘s default constructor. But it doesn’t have one.

You either have to provide a default constructor for the vector class, or explicitly initialize the members of rayToCast. One way is to do like this:

rayToCast(B angle, Vector2<A> origin, Vector2<A> point1, Vector2<A> point2)
   : RAngle(angle), point1(point1), point2(point2)
{ }