https://code.google.com/p/marsrovertechchallenge/

rover.rb

class Rover
  attr_accessor :x, :y

  def initialize(x, y, direction)
    @x = x
    @y = y
    @direction = direction

    @commands = []
  end

  def run(commands)
    @commands = commands.split('')

    @commands.each do |command|
      execute_command(command)
    end
  end

  def position
    puts "current position: #{@x} #{@y} #{@direction}"
  end

  private

  def execute_command(command)
    case command
    when 'L'
      turn_left
    when 'R'
      turn_right
    when 'M'
      move
    end
  end

  def turn_left
    case @direction
    when 'N'
      @direction = 'W'
    when 'E'
      @direction = 'N'
    when 'S'
      @direction = 'E'
    when 'W'
      @direction = 'S'
    end
  end

  def turn_right
    case @direction
    when 'N'
      @direction = 'E'
    when 'E'
      @direction = 'S'
    when 'S'
      @direction = 'W'
    when 'W'
      @direction = 'N'
    end
  end

  def move
    case @direction
    when 'N'
      @y += 1
    when 'E'
      @x += 1
    when 'S'
      @y -= 1
    when 'W'
      @x -= 1
    end
  end
end

rover = Rover.new(1, 2, 'N')
rover.run('LMLMLMLMM')
rover.position

rover = Rover.new(3, 3, 'E')
rover.run('MMRMMRMRRM')
rover.position