Overloading unary operators

[Dazzer]

Hi folks,

This from Learncpp.com

class Point
{
private:
    double m_dX, m_dY, m_dZ;
 
public:
    Point(double dX=0.0, double dY=0.0, double dZ=0.0)
    {
    m_dX = dX;
    m_dY = dY;
    m_dZ = dZ;
    }
 
    // Convert a Point into it's negative equivalent
    friend Point operator- (const Point &cPoint);
 
    // Return true if the point is set at the origin
    friend bool operator! (const Point &cPoint);
 
    double GetX() { return m_dX; }
    double GetY() { return m_dY; }
    double GetZ() { return m_dZ; }
};
 
// Convert a Point into it's negative equivalent 
Point operator- (const Point &cPoint)
{
    return Point(-cPoint.m_dX, -cPoint.m_dY, -cPoint.m_dZ);
}
 
// Return true if the point is set at the origin
bool operator! (const Point &cPoint)
{
    return (cPoint.m_dX == 0.0 &&
        cPoint.m_dY == 0.0 &&
        cPoint.m_dZ == 0.0);
}

I don't understand:

With overloading the "-" operator, he uses:

Point operator- (const Point &cPoint)

But with overloading the "!" op’, he uses:

bool operator! (const Point &cPoint)

But why isn’t it?:

Point operator! (const Point &cPoint)

What is fundamentaly different about the "-" & "!" unary operators that means the "-" overload puts the class as the function type, but with the "!" overload, it puts "bool" as the function type?

Thanks! ............D

[LB]

You say "function type", but that is not the correct word. What you mean to say is "return type", and it may help to get a refresher on functions to understand what return types are:
http://www.cplusplus.com/doc/tutorial/functions/

To answer your question directly, the unary ! operator (unary logical not) is traditionally used to obtain a value of type bool

[Dazzer]

Thanks! Yes indeed, i'm still struggling to call things by the right name, but i'm working on it! :)