How can I fix This error and what is the cause of it?

Question

I get an error and when i click to see the error i takes me to a document called xutility.

This is the two errors:

Error C2064 term does not evaluate to a function taking 2 arguments. Studio\2019\Community\VC\Tools\MSVC\14.21.27702\include\xutility 624

2.Error C2056 illegal expression Funtwo C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.21.27702\include\xutility 624

Then when i looked at line 624 it shows me this

// FUNCTION TEMPLATE _Debug_lt_pred
template <class _Pr, class _Ty1, class _Ty2>
constexpr bool _Debug_lt_pred(_Pr&& _Pred, _Ty1&& _Left, _Ty2&& _Right) _NOEXCEPT_COND(
    noexcept(_Pred(_Left, _Right))
    && noexcept(_Pred(_Right, _Left))) { // test if _Pred(_Left, _Right) and _Pred is strict weak ordering
    const auto _Result = static_cast<bool>(_Pred(_Left, _Right));
    if (_Result) {
        _STL_VERIFY(!_Pred(_Right, _Left), "invalid comparator");
    }

    return _Result;
}

My class:

class Vector3D : public Vector2
{
public:

    Vector3D();
    ~Vector3D();
    double GetMagnitude();
    void Normalize();
    void scale(Vector3D vector);
    void scale(double vector3x, double vector3y, double vector3z);

    Vector3D operator -();
    Vector3D operator +(Vector3D other);
    Vector3D operator -(Vector3D other);
    Vector3D operator *(Vector3D other);
    Vector3D operator /(Vector3D other);

    bool operator < (Vector3D other);
    bool operator > (Vector3D other);
    bool operator <= (Vector3D other);
    bool operator >= (Vector3D other);
    bool operator == (Vector3D other);
    bool operator != (Vector3D other);

    void operator = (Vector3D other);
    void operator += (Vector3D other);
    void operator -= (Vector3D other);
    void operator *= (Vector3D other);
    void operator /= (Vector3D other);

    friend ostream& operator <<(ostream& out, const Vector3D& v);
    friend istream& operator >>(istream& in, Vector3D& v);

    double m_z = 0;
};

< operator Implementation

bool Vector3D::operator<(Vector3D other)
{
    if (GetMagnitude() < other.GetMagnitude())
        return true;
    return false;
}

For the Implementation of each member:

Vector3D::Vector3D()
{
}

Vector3D::~Vector3D()
{
}

double Vector3D::GetMagnitude()
{
    return sqrt(pow(m_x, 2) + pow(m_y, 2) + pow(m_z, 2));
}

void Vector3D::Normalize()
{
    double maxValue = std::max(m_x, m_y, m_z);
    m_x = m_x / maxValue;
    m_y = m_y / maxValue;
    m_z = m_z / maxValue;
}

void Vector3D::scale(Vector3D vector)
{
    m_x *= vector.m_x;
    m_y *= vector.m_y;
    m_z *= vector.m_z;
}

void Vector3D::scale(double vector3x, double vector3y, double vector3z)
{
    m_x *= vector3x;
    m_y *= vector3y;
    m_z *= vector3z;
}

Vector3D Vector3D::operator-()
{
    Vector3D v;
    v.m_x = -m_x;
    v.m_y = -m_y;
    v.m_z = -m_z;
    return v;
}

Vector3D Vector3D::operator+(Vector3D other)
{
    Vector3D v;
    v.m_x = m_x + other.m_x;
    v.m_y = m_y + other.m_y;
    v.m_z = m_z + other.m_z;
    return v;
}

Vector3D Vector3D::operator-(Vector3D other)
{
    Vector3D v;
    v.m_x = m_x - other.m_x;
    v.m_y = m_y - other.m_y;
    v.m_z = m_z - other.m_z;
    return v;
}

Vector3D Vector3D::operator*(Vector3D other)
{
    Vector3D v;
    v.m_x = m_x * other.m_x;
    v.m_y = m_y * other.m_y;
    v.m_z = m_z * other.m_z;
    return v;
}

Vector3D Vector3D::operator/(Vector3D other)
{
    Vector3D v;
    v.m_x = m_x / other.m_x;
    v.m_y = m_y / other.m_y;
    v.m_z = m_z / other.m_z;
    return v;
}

bool Vector3D::operator<(Vector3D other)
{
    if (GetMagnitude() < other.GetMagnitude())
        return true;
    return false;
}

bool Vector3D::operator>(Vector3D other)
{
    if (GetMagnitude() > other.GetMagnitude())
        return true;
    return false;
}

bool Vector3D::operator<=(Vector3D other)
{
    if (GetMagnitude() <= other.GetMagnitude())
        return true;
    return false;
}

bool Vector3D::operator>=(Vector3D other)
{
    if (GetMagnitude() >= other.GetMagnitude())
        return true;
    return false;
}

bool Vector3D::operator==(Vector3D other)
{
    if (GetMagnitude() == other.GetMagnitude())
        return true;
    return false;
}

bool Vector3D::operator!=(Vector3D other)
{
    if (GetMagnitude() != other.GetMagnitude())
        return true;
    return false;
}

void Vector3D::operator=(Vector3D other)
{
    m_x = other.m_x;
    m_y = other.m_y;
    m_z = other.m_z;
}

void Vector3D::operator+=(Vector3D other)
{
    m_x += other.m_x;
    m_y += other.m_y;
    m_z += other.m_z;
}

void Vector3D::operator-=(Vector3D other)
{
    m_x -= other.m_x;
    m_y -= other.m_y;
    m_z -= other.m_z;
}

void Vector3D::operator*=(Vector3D other)
{
    m_x *= other.m_x;
    m_y *= other.m_y;
    m_z *= other.m_z;
}

void Vector3D::operator/=(Vector3D other)
{
    m_x /= other.m_x;
    m_y /= other.m_y;
    m_z /= other.m_z;
}

ostream& operator<<(ostream& out, const Vector3D& v)
{
    out << v.m_x << ", " << v.m_y << ", " << v.m_z;
    return out;
}

istream& operator>>(istream& in, Vector3D& v)
{
    cout << "Vector 2 Input" << endl << "x:";
    in >> v.m_x;

    cout << "y : ";
    in >> v.m_y;

    cout << "z : ";
    in >> v.m_z;

    return in;
}

I am just inheriting two members from class vector 2. They are x and y. m_x and m_y.

Have you posted _all_ your code? Where's your call for this? Where is the implementation? — Water, Sep 18 '19 at 04:58
You are not following the usual guidelines for operator overloading regarding `const`-ness of objects. See https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading. — R Sahu, Sep 18 '19 at 05:05
@Mario Is this also everything? Where are you instantiating and using the class? — Water, Sep 18 '19 at 14:08
Also small recommendation: You can convert this into a one liner: `bool Vector3D::operator<(Vector3D other) { return GetMagnitude() < other.GetMagnitude(); }` — Water, Sep 18 '19 at 14:08

score 3 · Accepted Answer · answered Sep 18 '19 at 05:06

You are attempting to alter the behaviour of the operators. Don't do that! Const correctness is not optional wrt operators. These are the operators you have declared incorrectly (and how they should have been declared).

    Vector3D operator -() const;
    Vector3D operator +(const Vector3D& other) const;
    Vector3D operator -(const Vector3D& other) const;
    Vector3D operator *(const Vector3D& other) const;
    Vector3D operator /(const Vector3D& other) const;

    bool operator < (const Vector3D& other) const;
    bool operator > (const Vector3D& other) const;
    bool operator <= (const Vector3D& other) const;
    bool operator >= (const Vector3D& other) const;
    bool operator == (const Vector3D& other) const;
    bool operator != (const Vector3D& other) const;

    // non-const methods, that return mutable reference to this. 
    Vector3D& operator = (const Vector3D& other);
    Vector3D& operator += (const Vector3D& other);
    Vector3D& operator -= (const Vector3D& other);
    Vector3D& operator *= (const Vector3D& other);
    Vector3D& operator /= (const Vector3D& other);

I'm assuming the error is because it is attempting to call operator < on a pair of vectors, however they are both const, and so no existing overload of operator < can work on the values (because they are both const).

I have change getmagnitude to getmagnitude()const too but i still get the same errors — Mario, Sep 18 '19 at 05:32

How can I fix This error and what is the cause of it?

1 Answers1