pingpong.pony

actor Ping
  var _passes: U32
  var _main: Main

  new create(passes: U32, main: Main) =>
    _passes = passes
    _main = main

  be ping(partner: Pong) =>
    if (_passes > 0) then
      partner.pong(this)
      _passes = _passes - 1
    else
      _main.done()
    end

actor Pong
  be pong(partner: Ping) => 
    partner.ping(this)

actor Main
  var _env: Env
  var _pass: U32 = 0

  new create(env: Env) =>
    _env = env

    try
      _pass = _env.args(1).u32()
    else
      _env.out.print("provide message count to pass")
    end

    let ping = Ping(_pass, this)
    let pong' = Pong
    ping.ping(pong')    

  be done() =>
    _env.out.print("done.")