13.4. Another constructor¶

Now that we have a card_deck object, it would be useful to initialize the cards in it. From the previous chapter we have a function called build_deck that we could use (with a few adaptations), but it might be more natural to write a second card_deck constructor.

card_deck::card_deck () {
  std::vector<playing_card> temp (52);
  cards = temp;

  std::size_t i = 0;
  for (int m_suit = clubs; m_suit <= spades; ++m_suit) {
    for (int m_rank = ace; m_rank <= king; ++m_rank) {
      cards[i].m_suit = static_cast<card_suit>(m_suit);
      cards[i].m_rank = static_cast<card_rank>(m_rank);
      i++;
    }
  }
}

Notice how similar this function is to build_deck, except that we had to change the syntax to make it a constructor. Now we can create a standard 52-card deck with the simple declaration card_deck deck;

The active code below prints out the cards in a deck using the loop from the previous section.

Example c192_deck_constructor_ac_1

 1#include <cstddef>
 2#include <iostream>
 3#include <string>
 4#include <vector>
 5
 6enum card_suit { clubs, diamonds, hearts, spades };
 7
 8enum card_rank { ace=1, two, three, four, five, six, seven, eight, nine,
 9ten, jack, queen, king };
10
11struct playing_card {
12    card_rank m_rank;
13    card_suit m_suit;
14    playing_card ();
15    playing_card (card_suit s, card_rank r);
16    void print () const;
17};
18
19struct card_deck {
20    std::vector<playing_card> cards;
21    card_deck ();
22};
23
24int main() {
25    card_deck deck;
26    for (std::size_t i = 0; i < 52; i++) {
27        deck.cards[i].print();
28    }
29}

Based on your observations from the active code above, the cards in deck are initialized to the correct suits and ranks of a standard deck of 52 cards.

True - we used the build_deck function with a few modifications to do this.

How do we create the deck?

True - we wrote a deck constructor to do this.

The for loops in the deck constructor initialize each card to its proper value.

False - we used the build_deck function with a few modifications to do this.

Look at the active code. How do we create the deck?

False - we wrote a deck constructor to do this.

Look at the active code.

Let's write a constructor for a deck of cards that uses 40 cards. This deck uses all 4 suits and ranks Ace through 10, omitting all face cards.

```
        i++;
      }
   }
}
```
```
card_deck::card_deck () {
```
```
cards = temp;
std::size_t i = 0;
```

cards[i].m_suit = m_rank;
cards[i].m_rank = m_suit;

cards[i].m_suit = static_cast<card_suit>(m_suit);
cards[i].m_rank = static_cast<card_rank>(m_rank);

for (card_rank m_rank = ace; m_rank <= ten; m_rank = card_rank(m_rank+1)) {

for (card_suit m_suit = clubs; m_suit < spades; m_suit = card_suit(m_suit+1)) {

for (int m_rank = ace; m_rank <= king; ++m_rank) {

for (int m_suit = clubs; m_suit <= spades; ++m_suit) {

```
std::vector<playing_card> temp (40);
```
```
std::vector<playing_card> temp (52);
```