Default value for parameter of class where value is another class

Title may be a little bit confusing but basically I have a class ‘Quaternion’ which has 2 parameters, the first being another instance of a class Vector3 and the other being a float.

Vector3 takes 3 floats as parameters and assigns them to x, y, and z.

I want to set default parameters for the Quaternion class but I am unsure how to set default parameters with a class as a parameter.

Vector3

class Vector3 {
  public:
    float x, y, z;

    Vector3(float uX, float uY, float uZ) {
      this->x = uX;
      this->y = uY;
      this->z = uZ; 
    }
};

Quaternion

class Quaternion {
  public:
    Vector3 axis;
    float scalar;

    Quaternion(Vector3 uAxis, float uScalar = 0) {
      axis = uAxis;
      scalar = uScalar;
    };
};

I would like to have the default parameter for uAxis to be a Vector3 with x, y, and z set to 1, 0, 0 respectively, but i am unsure how i can do this.

>Solution :

I think this is what you were looking for:

class Quaternion {
  public:
    Vector3 axis;
    float scalar;

    Quaternion(Vector3 uAxis = Vector3(1.0, 0.0, 0.0), float uScalar = 0) {
      axis = uAxis;
      scalar = uScalar;
    };
};

It is possible to call a constructor of a class to set a default parameter. Here is the corresponding cpp reference default arguments.