Question

I am currenty doing a Sudoku game in c++. For that , I defined many classes including,
class Pos for position, and class Error for maintaining errors.

Now, in class Pos,

class Pos {
    int x;
    int y;
public:
    Pos();
    Pos(Pos const&);
    Pos(int,int);

    void    setPos(int,int);

    void    setx(int);
    void    sety(int);

    int    getx() const ;
    int    gety() const ;

    string getPosReport();

    virtual ~Pos();

}; 

What I have done:
I have restricted the value for x and y to lie between 0-9 by writing setx and sety as,

void Pos::setx(int x){
    if((x < 0) & (x > 9))
        throw  Exception("Invalid Position");
    else
        this->x = x;
}

void Pos::sety(int y){
    if((y < 0) & (y > 9)){
        throw Exception("Invalid Position");
    }
    else
        this->y = y;
}

My Problem: How Pos() must be defined.

What I have worked:

1. Removing default constructor, didnt helped me because,

   class Error {
       string errmsg;    
       Pos pos1,pos2; // Pos() must be called!! default constructor cannot be removed!
       bool isError;
       // ...... 
   }
   

2. I can initialize x and y to -1 in Pos() , but I feel that will bring instability in my code.

3. I can have int* x and int* y in class Pos such that I can have x = y = NULL, but I feel Pointers will make my code relatively complex than now.

   so,it will be better if some one gives a solution which stimulates the scenario like x = y = N/A (not applicable)

Answer 1

Give Error only constructors that initialise the Pos member objects. Then you won’t need to default-construct Pos anywhere.

Initialising members is done with the “member initialisation list”, which you may find after the colon (:) below.

class Error {
   Pos p;

   public:
     Error() : p(1,2) {};
};

This should be covered in your book.

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• Top credit for correctly identifying valid solutions, and the reasons not to adopt them.