Question

I am creating a pair1 class for a x and y Cartesian coordinate system. x and y are doubles. I need to have 3 constructors.

1. No arguments, defaults x and y to zero.
2. One arguement assigns x and defaults y to zero.
3. One arugeument defaults x to zero and assigns y. I’m not sure if I am setting up the class right. I get the follwing error: pair1::pair1(double) and pair1::pair1(double) cannot be overloaded.

My class:

class pair1
{
private:
    double x;
    double y;

public:
    pair1(){ x = 0.0, y = 0.0; }    
    pair1( double a ){ x = a; y =0.0; }
    pair1(double b){ x = 0.0;  y = b; }
};

Answer 1

1) no arguments, defaults x and y to
zero.

That’s easy

2) one arguement assigns x and
defaults y to zero.

3) one arugeument
defaults x to zero and assigns y.

That’s a problem. How do you know, when you only have one parameter, which of the two is meant to be called? That’s why you get a compilation error.

Instead – use the default constructor (the one with no parameters), full constructor (the one with both), if needed, and SetX() and SetY() to set the X and Y separately, and make distinction by the name of the function.

class pair1
{
    private:
    double x;
    double y;

    public:
    pair1( double a=0.0, double b=0.0 ){ x = a; y =b; };
                     // default value 0.0 allows to only
                     // set x, and leave y to be the default,
                     // or leave them both default.
    void SetX(double a) { x=a;};
    void SetY(double b) { y=b;};
};