Postfix incrementer overloading for nested enumerated types

Question

I am having difficulty figuring out how to overload the postfix increment operator for an nested enumerated type of class Card. Moreover, I am also having difficulty getting copy assignment to work for this class. I am getting the following errors "operator++ must take one or zero arguments." Then, when I attempt to provide assignment I get

no match for operator= in ((deck*)->this)->Deck::deckArr = operator new 

---

class Card {
  public:
    enum Suit {
      SPADES,
      HEARTS,
      CLUBS,
      DIAMONDS
    };

    enum Spot {
      DEUCE,
      THREE,
      FOUR,
      FIVE,
      SIX,
      SEVEN,
      EIGHT,
      NINE,
      TEN,
      JACK,
      QUEEN,
      KING,
      ACE
   };

   Card();
   Card(Card&);
   Card(Suit&, Spot&);
   ~Card();

   Suit& operator++(Suit&,int);
   Spot& operator++(Spot&,int);
   Card& operator=(const Card&);

 private:
   Spot _spot;
   Suit _suit;
};

Card::Suit& Card::operator++(Card::Suit &s, int) {Card::Suit oldsuit = s;
                                            s = (Card::Suit)(s+1);
                                            return oldsuit;}
Card::Spot& Card::operator++(Card::Spot &sp, int){Card::Spot oldspot = sp;
                                            sp = (Card::Spot)(sp+1);
                                            return oldspot;}
Card& Card::operator=(const Card &c){_spot = c._spot; _suit = c._suit; return *this;}


#include "card.h"

class Deck {
 public:
    Deck();
    Deck(Deck&);
    ~Deck();

    void createDeck();
    void shuffleDeck(int);
 private:
    static const int DECK_SIZE = 52;
    Card deckArr[DECK_SIZE];
};

void Deck::createDeck(){
    int x = 0;
    for(Card::Suit s = Card::SPADES; s <= Card::HEARTS; s++){
        for(Card::Spot n = Card::DEUCE; n <= Card::ACE; n++, x++){
             deckArr[x] = new Card(s, n);
        }
    }
}

Answer 1

There are two ways to overload operator++,

Card::Suit operator++(int){ } //would be suit++

and

Card::Suit& operator++() { } //would be ++suit

You must not pass anything to operator++, except a dummy parameter (usually int) and usually you don't pass back a reference in postfix.

See here for some information.

Answer 2

The problem is that there is no way you can use a member operator here. A member operator always operates on the class of which it is a member, and since you want it to operator on an enum, and not on a class, it cannot be a member.

If you want ADL to find it, you'll have to make it a friend, in order to declare (and possibly define it) inside the class:

friend Suit& operator++( Suit& s )
{
    s = static_cast<Suit>( s + 1 );
    return s;
}
friend Suit operator++( Suit& s, int )
{
    Suit result( s );
    s ++;
    return result;
}

and the same for Spot.

You'll also have to decide what to do when you iterate beyond the end. Casting s + 1 back to the enum type is undefined behavior, at least in the case of Suit. A common convention is to add an extra value for the end at the end; e.g. END_Suit and END_Spot. This allows simple and safe iteration:

for ( Suit s = SPADES; s != END_Suit; ++ s ) // ...

Otherwise, it gets tricky.