这个问题是比较经典的啦，基本所有语言的多线程都会涉及到，但是没想到Lua的这个这么复杂 抓狂
看了好长时间才算看明白，先上个逻辑图：
开始时调用消费者，当消费者需要值时，再调用生产者生产值，生产者生产值后停止，直到消费者再次请求。设计为消费者驱动的设计。
图画的不太好，可以先将Filter遮住，它是过滤器对两个程序之间传递的信息进行处理。去掉Filter逻辑就更清晰些了，就是两个“线程”（其实是两个协同程序）互相调用。resume回到yield处开始，支持嵌套，返回到栈顶的yield位置。yield是非阻塞的“线程同步”。这到有点像linux里的管道通信。
function receive(prod) print("receive is called") local status,value = coroutine.resume(prod) return valueendfunction send(x,prod) print("send is called") return coroutine.yield(x)endfunction producer() return coroutine.create(function () print("producer is called") while true do print("producer run again") local x = io.read() send(x) end end)endfunction filter(prod) return coroutine.create(function () for line = 1,1000 do print("enter fliter "..line) local x = receive(prod) print("receive in filter finished") x= string.format("%5d %s",line,x) send(x,prod) end end)endfunction consumer(prod) print("consumer is called") while true do print("consumer run again") local x = receive(prod) print("retrun customer") io.write(x,"/n") endendp = producer()f=filter(p)consumer(f)
运行结果：
consumer is calledconsumer run againreceive is calledenter fliter 1receive is calledproducer is calledproducer run againfsysend is calledreceive in filter finishedsend is calledretrun customer 1 fsyconsumer run againreceive is calledenter fliter 2receive is calledproducer run againgagasend is calledreceive in filter finishedsend is calledretrun customer 2 gagaconsumer run againreceive is calledenter fliter 3receive is calledproducer run again......
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