Programming a Slot Machine

We’ll practice a bit, sum up everything we’ve learned so far, and implement a simple one-armed bandit game. We will put some money in the bank, pull the handle, and see what happens.

Outline

Let’s outline our plan. Variable balance will represent the amount of money we have in the bank. We’ll have three slot reels and a few images. Traditionally, slot machines have images of fruits, a cherry, a bell, and the number 7. To simplify our task, we’ll use the numbers from 0 to 5 instead of the images mentioned above. We can always revisit our game and make changes to it.

Variables x, y, and z will represent the reels. Each reel can hold only one value, from 0 to 5, at a time. A random number generator will define this value.

Win or lose

The next step is to define what “win” and “lose” mean. When all three variables x, y, and z are equal, we’ll enforce the following rules:

• If all the numbers are zeroes, the player will lose everything.
• If all the numbers are ones, $10 will be added to the player’s balance.
• If all the numbers are twos, $20 will be added to the player’s balance.
• Otherwise, the player will be charged 50 cents for each attempt.

The program should work until we have no money remaining in our balance.

An age check will be helpful:

print "What's your age: "
age = gets.to_i
if age < 18
  puts 'Sorry, but you should be at least 18 to play'
  exit
end

The balance variable keeps the balance initialized with $20, and it also defines the infinite loop:

balance = 20
loop do
  # ..
end

Wait for the “Enter” key inside of the loop:

  puts 'Press Enter to pull the handle...'
  gets

Initialize variables x, y, and z:

  x = rand(0..5)
  y = rand(0..5)
  z = rand(0..5)

Print the result of a single draw:

  puts "Result: #{x} #{y} #{z}"

Check the first condition, which is “If all the numbers are zeroes, the player will lose everything”:

  if x == 0 && y == 0 && z == 0
    balance = 0
    puts 'You lost your money'
  end 

Check the second condition, which is “If all the numbers are ones, $10 will be added to the player’s balance”:

  elsif x == 1 && y == 1 && z == 1
    balance += 10
    puts 'You won $10'
  end

And finally, check the third condition, which is “If all the numbers are twos, $20 will be added to our balance.” We also cover the last case “Otherwise, the player will be charged 50 cents for each attempt”:

Here is the complete code for all conditions:

  if x == 0 && y == 0 && z == 0
    balance = 0
    puts 'You lost your money'
  elsif x == 1 && y == 1 && z == 1
    balance += 10
    puts 'You won $10'
  elsif x == 2 && y == 2 && z == 2
    balance += 20
    puts 'You won $20'
  else
    balance -= 0.5
    puts 'You lost 50 cents'
  end

At the end, we will show the final result:

  puts "Your balance is #{balance} dollars"  

Complete program

Press the “Run” button to execute the program below: