Bowling Game in Ruby

John Cleary (@TheRealBifter) is doing a nice project - The 12 TDD's of Xmas. Day 9 was the Bowling Game problem. I did it in Ruby. Here's the code from traffic-light 100.

Tests first:

require './score'
require 'test/unit'

class TestScore < Test::Unit::TestCase

  def test_score_uninteresting_game
    #           7     7     7     7    7 = 35
    #        6     6     6     6     6   = 30
    balls = "51|52|51|52|51|52|51|52|51|52"
    assert_equal 65, score(balls)
  end

  def test_score_all_frames_5_spare
    #           15    15    15    15    15 = 75
    #        15    15    15    15    15    = 75
    balls = "5/|5/|5/|5/|5/|5/|5/|5/|5/|5/|5"
    assert_equal 150, score(balls)
  end

  def test_perfect_score
    #          30  30  30  30  30 = 150
    #        30  30  30  30  30   = 150
    balls = "X|X|X|X|X|X|X|X|X|X|XX"
    assert_equal 300, score(balls)
  end

  def test_10_strikes_then_33
    #          30  30  30  30  16 = 136
    #        30  30  30  30  23   = 143
    balls = "X|X|X|X|X|X|X|X|X|X|33"
    assert_equal 279, score(balls)
  end

  def test_game_with_spare_in_middle_of_strikes
    #          20   30  30  30  30    = 140
    #        25  20   30  30  30      = 135
    balls = "X|X|5/|X|X|X|X|X|X|X|XX" 
    assert_equal 275, score(balls)
  end

  def test_game_with_strike_in_middle_of_spares
    #           15    20   15    13    20  = 83
    #        13    11    20   14    12     = 70
    balls = "2/|3/|5/|1/|X|3/|5/|4/|3/|2/|X"
    assert_equal 153, score(balls)
  end

  def test_game_with_zero_balls
    #           8     7     7     7     7 = 36
    #        6     5     6     6     6    = 29
    balls = "51|62|50|52|51|52|51|52|51|52"
    assert_equal 65, score(balls)
  end

  def test_game_with_dash_as_zero_balls
    #           8     7     7     7     8 = 37
    #        6     5     6     6     6    = 29
    balls = "51|62|5-|52|51|52|51|52|51|62"
    assert_equal 66, score(balls)
  end

end

Code second:

def score(balls)
  frames = (balls).split("|")
  while frames.length != 12
    frames << "0"
  end
  frames.each_cons(3).collect{ |frame| 
    frame_score(frame)
  }.inject(:+)
end

def frame_score(frames)
  if strike? frames[0]
    10 + strike_bonus(frames[1..2])
  elsif spare? frames[0]
    10 + ball_score(frames[1][0]) 
  else
    frames[0].chars.collect{ |ball| 
      ball_score(ball)
    }.inject(:+)
  end
end

def strike_bonus(frames)
  if frames[0] == "XX"
    20
  elsif strike? frames[0]
    10 + ball_score(frames[1][0])
  elsif spare? frames[0]
    10
  else
    ball_score(frames[0][0]) + ball_score(frames[0][1])
  end
end

def ball_score(ball)
  if strike? ball
    10
  else
    ball.to_i
  end
end

def strike?(frame)
  frame == "X"
end

def spare?(frame)
  frame[-1] == "/"
end

It took me a while to realize that each_slice should have been each_cons. You can replay my entire progression (warts and all) on Cyber-Dojo (naturally).