class Instructions

# File bin/tm, line 64
def initialize(filename)
  re = Regexp.compile('\s* (\w+) \s+ (\w) \s+ (\w+) \s+ (\w) \s+ ([RL])',
      Regexp::EXTENDED)
  @instructions = Hash.new { |hash, key| hash[key] = Hash.new }

  File.open(filename) do |file|
    file.each_line do |line|
      if data = re.match(line) then
        st = data[1].to_sym
        ch = data[2]
        @instructions[st][ch] = Transition.new(*data[3 .. 5])

        if self.initial_state.nil?
          self.initial_state = st
        end
      end
    end
  end
end

# File bin/tm, line 84
def get_transition(state, char)
  if @instructions.has_key?(state) && @instructions[state].has_key?(char)
    return @instructions[state][char]
  else
    return nil
  end
end

# File bin/tm, line 92
def run(tape, state = self.initial_state)
  raise("Invalid tape") unless
    tape.respond_to?(:left)  &&
    tape.respond_to?(:right) &&
    tape.respond_to?(:read)  &&
    tape.respond_to?(:write)

  while t = get_transition(state, tape.read)
    state = t.apply do |ch, dir|
      tape.write(ch)
      case dir
        when 'L'
          tape.left
        when 'R'
          tape.right
        else
          raise "Invalid direction"
      end
      puts tape if VERBOSE
    end
  end
end