Initialize an array with a loop in Ruby

Question

I'm coming to Ruby from Java and not really comfortable with it on the second day. What I'm doing is to initialize decks of cards with a given number of decks. Say I will be playing with 2 decks of cards, 52 cards in each deck, and thus 104 cards in total (Jokers are not used). My program goes:

def initialize(num)
    @num_of_decks = num
    # initialize my cards here...
end

After initialization, I want my cards to be:

cards = {"Diamond A", "Diamond 2", ... "Diamond K", 
         "Club A", ...
         ...
         "Spade A", ... "Spade K", // end of the first deck
         "Diamond A", ...
         ...
         "Spade A", ... "Spade K" // end of the second deck
        }

I want my program to be able to adapt to whatever num_of_decks is. I don't really have a clear feeling of how Ruby loops work by now, especially when it seems that for loops are discouraged in Ruby. Hopefully anyone can provide an example here so that I can study how it works.

You're mixing up your syntaxes, that's not valid Ruby. Arrays use [], hashes use {}. — user229044
– user229044 ♦, Commented Jan 28, 2014 at 19:29
If you're coming from a Java background, you should be able to think your way through this. It's relatively straight-forward coding problem. The steps you'd take would be identical, though the syntax will be different and the results might not be as idiomatic as they could be. — user229044
– user229044 ♦, Commented Jan 28, 2014 at 19:33

Matt · Accepted Answer · 2014-01-28 20:56:25Z

4

faces = %w( A 2 3 4 5 6 7 8 9 10 J Q K )
suits = %w( Diamond Club Heart Spade )
deck = suits.product(faces).map { |p| p.join ' ' }

def initialize(num)
  @num_of_decks = num
  cards = deck * num
end

edited Jan 28, 2014 at 20:56

answered Jan 28, 2014 at 19:43

Matt

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Comments

Ajedi32 · Accepted Answer · 2014-01-28 20:14:50Z

3

Hmmm, I'm not entirely sure what you're asking, but perhaps something like this will work?

class DrawPile
  CARD_SUITS = ["Diamond", "Heart", "Spade", "Club"]
  CARD_FACES = ["A", *(2..10).map(&:to_s), "J", "Q", "K"]
  A_DECK = CARD_SUITS.product(CARD_FACES).map{|x| x.join " "}
  def initialize(num)
    @num_of_decks = num
    @cards = (A_DECK * num).shuffle
  end

  attr_reader :num_of_decks, :cards
end

Usage:

pile = DrawPile.new(2)
pile.num_of_decks #=> 2
pile.cards #=> ["Spade 2", "Spade K", "Heart 4", "Heart 7", ...]

edited Jan 28, 2014 at 20:14

answered Jan 28, 2014 at 19:43

Ajedi32

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Comments

hirolau · Accepted Answer · 2014-01-28 19:45:28Z

0

suits = ['spades', 'diamonds', 'clubs', 'hearts']
values = ['Ace', '2', '3', '4', 'Jack', 'Queen']
cards = suits.product(values).map{|suit, value| "#{value} of #{suit}"}

p cards #=> ["Ace of spades", "2 of spades", "3 of spades", "4 of spades", "Jack of spades"

answered Jan 28, 2014 at 19:45

hirolau

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Comments

sh03 · Accepted Answer · 2014-01-28 19:53:41Z

0

You can use:

a = ['Spade', 'Diamond', 'Club', 'Heart']
b = ['A', *('2'..'10'), 'J', 'Q', 'K']
cards = a.product(b).collect { |a| a.join(' ') }
total_cards = [*(cards * num_of_decks)]
# => ["Spade A", "Spade 2", "Spade 3", "Spade 4", ..., "Diamond A", "Diamond 2", "Diamond 3", ..., "Spade A", "Spade 2", "Spade 3", "Spade 4", ...]

And here is where you can play with it.

edited Jan 28, 2014 at 19:53

answered Jan 28, 2014 at 19:40

sh03

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