def new_interpreter(f, prog)
  prog = prog.clone
  input = Channel(Int32).new
  output = Channel(Int32?).new
  spawn do
    op = ""
    pc = 0
    arg = ->(i : Int32) { op[-(3+i)] == '0' ? prog[prog[pc+1+i]] : prog[pc+1+i] }
    loop do
      op = "0000" + prog[pc].to_s
      case op
      when .ends_with? "1"
        prog[prog[pc+3]] = arg.call(0) + arg.call(1)
        pc += 4
      when .ends_with? "2"
        prog[prog[pc+3]] = arg.call(0) * arg.call(1)
        pc += 4
      when .ends_with? "3"
        prog[prog[pc+1]] = input.receive
        pc += 2
      when .ends_with? "4"
        output.send(arg.call(0))
        pc += 2
      when .ends_with? "5"
        pc = arg.call(0) != 0 ? arg.call(1) : pc + 3
      when .ends_with? "6"
        pc = arg.call(0) == 0 ? arg.call(1) : pc + 3
      when .ends_with? "7"
        prog[prog[pc+3]] = arg.call(0) < arg.call(1) ? 1 : 0
        pc += 4
      when .ends_with? "8"
        prog[prog[pc+3]] = arg.call(0) ==  arg.call(1) ? 1 : 0
        pc += 4
      when .ends_with? "99"
        input.receive
        output.send(nil)
        break
      end
    end
  end
  {input, output}
end