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)

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
......