Lua笔记7 coroutine

1. 使用

co = coroutine.create(function() print("hi") end)  --创建
coroutine.status(co)   -- 获取状态, suspended
coroutine.resume(co)  -- 运行
coroutine.status(co)   -- 获取状态, dead

2.resume是在保护模式下运行的，所以错误信息是通过co的返回值来处理的

co = coroutine.create(function()
    for i=1,2 do
        print("co", i)
        coroutine.yield()   -- 挂起程序
    end
end)
print(coroutine.status(co)) -- suspended
coroutine.resume(co)        -- co 1
print(coroutine.status(co)) -- suspended
coroutine.resume(co)        -- co 2
print(coroutine.status(co)) -- suspended
print(coroutine.status(co)) -- dead
print(coroutine.resume(co)) -- false cannot resume dead coroutine

3. resume-yield交换数据

1) 第一次调用resume， 传给resume的参数就是传给co主程序的参数

co = coroutine.create(function(a, b)
    print(a, b)
end)

coroutine.resume(co, 1,2)   --  true
-- co 输出 1, 2

2) 之后调用resume, yield函数的返回值，是传给co的额外参数

co = coroutine.create(function(a, b)
    print("co", coroutine.yield())
end)

coroutine.resume(co)
coroutine.resume(co, 1,2)

3) 协同程序结束后，resume的返回值是协同主程序的返回值, 多值返回

co = coroutine.create(function(a, b)
    return a+b
end)

print(coroutine.resume(co, 1,2))    -- true 3

4. 管道

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

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

function producer()
    local i = 0
    return coroutine.create(function()
        while true do
            local x = i
            i = i + 1
            send(x)
        end
    end)
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)
        print("received:" .. x)
    end
end

consumer(filter(producer()))