Lua协程学习

按照书上码了下，但运行有问题，暂时不知道原因：

function send (x)
        coroutine.yield(x)
end

function producer()
  return coroutine.create( function ()
         while true do
          local x = 1
          send(x)
          end
        end)
end

function receive(prod)
        local status, value = coroutine.resume(prod)
        return value
end

function filter (prod)
        return coroutine.create(function()
                a = {1,2,3,4,5,6,7,8,9,10}
                for line , k in pairs(a) do
                local x = receive(prod)
                x = string.format("%5d %s",line,x)
                send(x)
                end
        end)
end

function consumer (prod)
        while true do
                local x = receive(prod)
                print(x)
        end
end

consumer(filter(producer()))

　　之后再来细看，主要是 producter-consumer模型。