Annoying problems with struct in c++

Question

My problem is that I don't know how to program things in c++ like I do in c#. So I don`t know what is the problem with my code. I'm trying to create two structs. One to represent a Matrix33 and the other a vector2d :

struct Vector2
{
    float x;
    float y;
    float h;

    Vector2()
    {
        x = y = h = 0;
    }
    Vector2(float valueX, float valueY, float valueH)
    {
        x = valueX;
        y = valueY;
        h = valueH;

    }
    Vector2(float valueX, float valueY)
    {
        x = valueX;
        y = valueY;
        h = 1;
    }


    Vector2 Translate(Vector2 dir)
    {
        Matrix33 matrix = Matrix33::GetIdentity();

        matrix.a02 = dir.x;
        matrix.a12 = dir.y;

        return matrix * Vector2(x, y, h);
    }

    static Vector2 VectorOne()
    {
        return Vector2(1, 1, 1);
    }
    static Vector2 VectorUP()
    {
        return Vector2(0, 1, 0);
    }
    static Vector2 VectorFoward()
    {
        return Vector2(0, 0, 1);
    }
    static Vector2 VectorRight()
    {
        return Vector2(1, 0, 0);
    }

    Vector2 operator*(const int value)
    {
        return Vector2(x*value, y*value, h);
    }
    Vector2 operator/(const int value)
    {
        return Vector2(x / value, y / value, 1);
    }
    Vector2 operator+(const Vector2 value)
    {
        return  Vector2(x + value.x, y + value.y);
    }
    Vector2 operator-(const Vector2 value)
    {
        return  Vector2(x - value.x, y - value.y);
    }

};

struct Matrix33
{
    float a00; float a01; float a02;
    float a10; float a11; float a12;
    float a20; float a21; float a22;

    Matrix33()
    {
        a00 = a01 = a02 = a10 = a11 = a12 = a20 = a21 = a22 = 0;
    }
    void AddValues(int line, float c1, float c2, float c3)
    {
        if (line == 0)
        {
            a00 = c1;
            a01 = c2;
            a02 = c3;
        }
        else if (line == 1)
        {
            a10 = c1;
            a11 = c2;
            a12 = c3;
        }
        else if (line == 2)
        {
            a20 = c1;
            a21 = c2;
            a20 = c3;
        }
    }

    static Matrix33 GetIdentity()
    {
        Matrix33 m;
        m.a00 = m.a11 = m.a22 = 1;

        return m;
    }

    Matrix33 operator*(const Matrix33 m)
    {
        Matrix33 result;
        result.AddValues(0, (a00*m.a00 + a01*m.a10 + a02*m.a20), (a00*m.a01 + a01*m.a11 + a02*m.a21), (a00*m.a02 + a01*m.a12 + a02*m.a22));
        result.AddValues(1, (a10*m.a00 + a11*m.a10 + a12*m.a20), (a10*m.a01 + a11*m.a11 + a12*m.a21), (a10*m.a02 + a11*m.a12 + a12*m.a22));
        result.AddValues(2, (a20*m.a00 + a21*m.a10 + a22*m.a20), (a20*m.a01 + a21*m.a11 + a22*m.a21), (a20*m.a02 + a21*m.a12 + a22*m.a22));

        return result;
    }
    Vector2 operator*(const Vector2 p)
    {
        Vector2 result;

        result.x = a00*p.x + a01*p.y + a02*p.h;
        result.y = a10*p.x + a11*p.y + a12*p.h;
        result.h = a20*p.x + a21*p.y + a22*p.h;

        return result;
    }

};

The problem is that when I try to build I`m getting a lot of erros related to the my matrix aN values and the static func GetIdentity(). I have no idea of what is going on here.

Error 7 error C2228: left of '.a12' must have class/struct/union
Error 16 error C2228: left of '.a12' must have class/struct/union Error 27 error C2228: left of '.a12' must have class/struct/union
Error 5 error C2228: left of '.a02' must have class/struct/union
Error 14 error C2228: left of '.a02' must have class/struct/union
Error 25 error C2228: left of '.a02' must have class/struct/union

Error 5 error C3861: 'GetIdentity': identifier not found
Error 16 error C3861: 'GetIdentity': identifier not found
Error 29 error C3861: 'GetIdentity': identifier not found
Error 4 error C2653: 'Matrix33' : is not a class or namespace name
Error 15 error C2653: 'Matrix33' : is not a class or namespace name
Error 28 error C2653: 'Matrix33' : is not a class or namespace name

Does anyone have some tips to help me here. I would appreciate a lot!. Thanks

Answer 1

Before defining any member function of class Vector2 that deals with elements of class Matrix3 you have to define class Matrix3. And only after the definition of Matrix3 you may define these member functions of class Vector2.

For example

struct Vector2
{
    float x;
    float y;
    float h;

    Vector2()
    {
        x = y = h = 0;
    }
    Vector2(float valueX, float valueY, float valueH)
    {
        x = valueX;
        y = valueY;
        h = valueH;

    }
    Vector2(float valueX, float valueY)
    {
        x = valueX;
        y = valueY;
        h = 1;
    }

    // not defined but only declared    
    Vector2 Translate(Vector2 dir);

    // other members of the class
};


struct Matrix33
{
    float a00; float a01; float a02;
    float a10; float a11; float a12;
    float a20; float a21; float a22;

    Matrix33()
    {
        a00 = a01 = a02 = a10 = a11 = a12 = a20 = a21 = a22 = 0;
    }
    void AddValues(int line, float c1, float c2, float c3)
    {
        if (line == 0)
        {
            a00 = c1;
            a01 = c2;
            a02 = c3;
        }
        else if (line == 1)
        {
            a10 = c1;
            a11 = c2;
            a12 = c3;
        }
        else if (line == 2)
        {
            a20 = c1;
            a21 = c2;
            a20 = c3;
        }
    }

    static Matrix33 GetIdentity()
    {
        Matrix33 m;
        m.a00 = m.a11 = m.a22 = 1;

        return m;
    }

    Matrix33 operator*(const Matrix33 m)
    {
        Matrix33 result;
        result.AddValues(0, (a00*m.a00 + a01*m.a10 + a02*m.a20), (a00*m.a01 + a01*m.a11 + a02*m.a21), (a00*m.a02 + a01*m.a12 + a02*m.a22));
        result.AddValues(1, (a10*m.a00 + a11*m.a10 + a12*m.a20), (a10*m.a01 + a11*m.a11 + a12*m.a21), (a10*m.a02 + a11*m.a12 + a12*m.a22));
        result.AddValues(2, (a20*m.a00 + a21*m.a10 + a22*m.a20), (a20*m.a01 + a21*m.a11 + a22*m.a21), (a20*m.a02 + a21*m.a12 + a22*m.a22));

        return result;
    }
    Vector2 operator*(const Vector2 p)
    {
        Vector2 result;

        result.x = a00*p.x + a01*p.y + a02*p.h;
        result.y = a10*p.x + a11*p.y + a12*p.h;
        result.h = a20*p.x + a21*p.y + a22*p.h;

        return result;
    }

};

// now you may define it
Vector2 Vector2::Translate(Vector2 dir)
{
    Matrix33 matrix = Matrix33::GetIdentity();

    matrix.a02 = dir.x;
    matrix.a12 = dir.y;

    return matrix * Vector2(x, y, h);
}

Answer 2

You actually don't have to make many changes. You can forward declare Vector2, move the definition of Vector2 after Matrix33, and then move the definition of your operator* outside of Matrix33. For example:

// Forward declaration
struct Vector2;

struct Matrix33
{
  // ...    
  Vector2 operator*(const Vector2 p); 
  // ^ declaration only because
  //   Vector2 is an incomplete type at this point
};

struct Vector2
{
 // ...
};

Vector2 Matrix33::operator*(const Vector2 p)
{
  Vector2 result;

  result.x = a00*p.x + a01*p.y + a02*p.h;
  result.y = a10*p.x + a11*p.y + a12*p.h;
  result.h = a20*p.x + a21*p.y + a22*p.h;

  return result;
}

Live example