luacoroutinefilter

function send (x)
coroutine.yield(x)
end
function producer ()
return coroutine.create (function ()
while true do
local x = io.read()
send(x)
end
end)
end
function receive (prod)
local status, value = coroutine.resume(prod)
return value
end
function filter (prod)
return coroutine.create(function ()
for line = 1, math.huge 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)
io.write(x, "\n")
end
end
p = producer()
f = filter(p)
consumer(f)