recieve = function()
    local x = select(2,coroutine.resume(producer))
    return x
end

producer = coroutine.create(function()
    local x
    while true do
        while true do
            x = io.read()
            if not tonumber(x) then
                break
            end
        end
        coroutine.yield(x)
    end
end)

print("Do not enter a number!")
while true do print(recieve()) end