A0A0.rb

class A0A0
  OPS = Hash[*%w[S + D - M * L <=>]]

  def initialize source
    @program = *source.lines
    @line = @program.index { |p| p['>'] } || 0
    @program.map! { |p| p.scan /\w-?\d+/ }
  end

  def debug
    @program.each_with_index do |p, i|
      puts "%c%d\t%s" % ['* '[i <=> @line], i, (p || []) * ' ']
    end
    puts '-' * 20
  end

  def line
    @program[@line]
  end

  def last modify
    begin
      line[-1] = line[-1].sub(/-?\d+/) { |o| modify[o.to_i] }
    rescue NoMethodError
      raise "No last number to modify."
    end
  end

  def run
    until line.empty?
      debug if $DEBUG
      insn = line.shift
      arg = insn[1..-1].to_i

      case insn
      when /A/ then (@program[@line + arg] ||= []).concat line
      when /C/ then @program[@line + arg] = []
      when /G/ then @line += arg
      when /O/ then print arg
      when /P/ then print (arg % 256).chr
      when /I/ then last -> _ { STDIN.getc.send %w[to_i ord][arg] }
      when /([SDML])/ then last -> o { o.send OPS[$1], arg }
      end

      @line += 1 unless insn['G']
      break unless line
    end
  end
end

$DEBUG = true
A0A0.new(ARGF).run