PlayingCards52

Cards from a standard deck of fifty two.

Pick a Card

A Card is a standard playing card from a fifty-two card deck. The following functions return a Card:

Card(suit,rank) where suit is one of the symbols :clubs, :diamonds, :hearts, or :spades and rank is an integer from 1 (for Ace) to 13 (for King).
Card(index) where index is an integer from 1 (for the Ace of Clubs) to 52 (for the King of Spades).
Card() returns a random card.

julia> using PlayingCards

julia> Card(:diamonds,12)
Q♢

julia> Card(49)
T♠

julia> Card()
Q♠

The function string returns a two-character representation of the Card:

julia> string(Card(22))
"9♢"

Alternative input

Cards can be entered via their two-character representation. For example, the nine of diamonds can be entered as 9♢. That is, type 9 then \diamondsuit and then TAB.

Face cards, tens, and aces can also be entered in this way (using the capital letters T, J, K, Q, and A followed by the suit symbol):

julia> c = K♠;

julia> println(c)
K♠

julia> T♡ == Card(:hearts,10)
true

These cards can also be entered with a leading 1, 10, 11, 12, or 13:

julia> 10♢
T♢

julia> 13♠
K♠

julia> 1♣
A♣

Note that the four suit symbols are defined as objects of type PlayingCards52.Suit:

julia> ♠    # type \spadesuit and then TAB
PlayingCards52.Suit(:spades)

Cards can be created either using either :spades or ♠:

julia> a = Card(:spades,5)
5♠

julia> b = Card(♠,5)
5♠

julia> a==b
true

Determine Properties

The functions suit and rank return the suit (as a Symbol) and the rank (as an Int) of the card.

julia> c = Card()
J♣

julia> suit(c)
:clubs

julia> rank(c)
11

The function index returns a distinct integer value (from 1 to 52) for the card.

julia> c = Card(17)
4♢

julia> index(c)
17

Use color to determine if the Card is red or black:

julia> C = Card(:clubs,9)
9♣

julia> color(C)
:black

julia> color(Card(27))  # this is the Ace of Hearts
:red

Ordering

Two Cards can be compared with the usual ordering operators (such as <). The ordering of cards is determined first by rank and, if of the same rank, by suit (alphabetically, as in bridge).

julia> Card(:diamonds,10) < Card(:hearts,10)
true

julia> Card(:diamonds,10) < Card(:clubs,10)
false

The ace_high function is used to determine if an Ace is higher or lower than the other ranks. Use ace_high(true) or ace_high(false) to set your preference. A call to ace_high() returns the current setting.

julia> ace_high()
true

julia> Card(:spades,1) < Card(:diamonds,5)
false

julia> ace_high(false)
false

julia> Card(:spades,1) < Card(:diamonds,5)
true

Dealing

The function deck() returns a 52-long array containing all possible cards in random order. Use deck(false) for them to be returned in a "new box" order.

Use the function print_deck() to see all 52 cards in four lines of thirteen cards each.

julia> d = deck(); print_deck(d)
2♠ J♢ K♠ 3♣ Q♢ 6♢ K♡ 9♣ A♠ 8♢ 7♡ J♣ 4♠
8♣ T♢ T♣ 2♢ 4♣ 3♡ T♡ 6♡ Q♣ A♣ 4♢ 8♡ 8♠
3♠ 3♢ 5♣ J♠ 5♢ 6♣ A♢ T♠ Q♡ 7♣ 9♠ 7♠ 6♠
Q♠ J♡ 7♢ 2♡ A♡ 9♢ 2♣ 4♡ 5♡ K♣ 9♡ 5♠ K♢

julia> d = deck(false); print_deck(d)
A♣ 2♣ 3♣ 4♣ 5♣ 6♣ 7♣ 8♣ 9♣ T♣ J♣ Q♣ K♣
A♢ 2♢ 3♢ 4♢ 5♢ 6♢ 7♢ 8♢ 9♢ T♢ J♢ Q♢ K♢
A♡ 2♡ 3♡ 4♡ 5♡ 6♡ 7♡ 8♡ 9♡ T♡ J♡ Q♡ K♡
A♠ 2♠ 3♠ 4♠ 5♠ 6♠ 7♠ 8♠ 9♠ T♠ J♠ Q♠ K♠

Deal a random poker hand like this:

julia> using ShowSet

julia> Set(deck()[1:5])
{2♠,6♢,6♡,T♠,K♣}

Shuffling

The deck() function returns a randomly shuffled deck of cards with all 52! possible orderings equally likely. However, if one wishes to manually randomize the deck, or to randomize an ordered deck as returned by deck(false), we provide the functions shuffle, riffle, and cut. These functions are typically applied to a full deck of 52 cards, but may be used on any list.

Shuffle

The functions shuffle and shuffle! from the Random module are imported and so may be applied to card decks. These functions apply a random permutation to the cards (all orders equally likely). The function shuffle returns a new deck, leaving the original deck unchanged. The function shuffle! overwrites the deck in the new order.

Riffle

The functions riffle and riffle! apply a random riffle shuffle to the deck using the Gilbert–Shannon–Reeds model. The former leaves the original deck unchanged and the latter overwrites the deck.

julia> d = deck(false); print_deck(d)
A♣ 2♣ 3♣ 4♣ 5♣ 6♣ 7♣ 8♣ 9♣ T♣ J♣ Q♣ K♣
A♢ 2♢ 3♢ 4♢ 5♢ 6♢ 7♢ 8♢ 9♢ T♢ J♢ Q♢ K♢
A♡ 2♡ 3♡ 4♡ 5♡ 6♡ 7♡ 8♡ 9♡ T♡ J♡ Q♡ K♡
A♠ 2♠ 3♠ 4♠ 5♠ 6♠ 7♠ 8♠ 9♠ T♠ J♠ Q♠ K♠

julia> riffle!(d); print_deck(d)
A♣ 4♡ 5♡ 6♡ 2♣ 3♣ 4♣ 7♡ 8♡ 9♡ T♡ J♡ Q♡
K♡ A♠ 2♠ 5♣ 6♣ 7♣ 8♣ 9♣ T♣ J♣ Q♣ K♣ A♢
3♠ 4♠ 5♠ 6♠ 7♠ 2♢ 3♢ 8♠ 4♢ 5♢ 6♢ 7♢ 9♠
8♢ 9♢ T♠ T♢ J♢ Q♢ J♠ K♢ Q♠ A♡ 2♡ K♠ 3♡

Note that a single riffle shuffle does a poor job at randomizing the deck.

Cut

The functions cut and cut! are used to cut the deck.

cut!(d,idx) moves cards 1 through idx to the back of the deck; the new first card is the one formerly at position idx+1.
cut!(d) cuts the deck a random index. If the deck has n cards, then the cut location is given by the binomial random variable B(n,1/2).

julia> d = deck(false);

julia> cut!(d)

julia> print_deck(d)
Q♢ K♢ A♡ 2♡ 3♡ 4♡ 5♡ 6♡ 7♡ 8♡ 9♡ T♡ J♡
Q♡ K♡ A♠ 2♠ 3♠ 4♠ 5♠ 6♠ 7♠ 8♠ 9♠ T♠ J♠
Q♠ K♠ A♣ 2♣ 3♣ 4♣ 5♣ 6♣ 7♣ 8♣ 9♣ T♣ J♣
Q♣ K♣ A♢ 2♢ 3♢ 4♢ 5♢ 6♢ 7♢ 8♢ 9♢ T♢ J♢

Acknowledgement

Developed with input from @charleskawczynski and in parallel with his PlayingCards.jl.

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