说明：  Retlang is a robust library for writing highly concurrent applications. The library borrows part of its name and design from Erlang. Retlang provides a concurrency solution that is quite different from basic locking solutions, Parallel FX, or the .NET thread pool. With Retlang, application components exchange messages asynchronously rather than using low level locking and blocking api s. Messages are delivered sequentially to prevent thread races or object synchronization. It is similar in design to event-based actors in Scala.