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 value
end
function send(x,prod)
print("send is called")
return coroutine.yield(x)
end
function producer()
return coroutine.create(function ()
print("producer is called")
while true do
print("producer run again")
local x = io.read()
send(x)
end
end)
end
function 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)
end
function consumer(prod)
print("consumer is called")
while true do
print("consumer run again")
local x = receive(prod)
print("retrun customer")
io.write(x,"\n")
end
end
p = producer()
f=filter(p)
consumer(f)
运行结果：
consumer is called consumer run again receive is called enter fliter 1 receive is called producer is called producer run again fsy send is called receive in filter finished send is called retrun customer 1 fsy consumer run again receive is called enter fliter 2 receive is called producer run again gaga send is called receive in filter finished send is called retrun customer 2 gaga consumer run again receive is called enter fliter 3 receive is called producer run again ......
