coroutine

Cooperative threads of Lua 5.1 / LuaJIT 2.1. A coroutine has its own stack and runs until it yields or finishes.

Functions

coroutine.create(f: function): thread

coroutine.create(f: function): thread

• Creates a new coroutine that will run f, and returns it. The coroutine starts suspended.

coroutine.resume(co: thread, ...: any): boolean, any

coroutine.resume(co: thread, ...: any): boolean, any

• Starts or continues the coroutine co. Extra arguments are passed to the body function on the first resume, or become the results of coroutine.yield on later resumes.
• On success returns true plus the values passed to yield, or the values returned by the body when it finishes.
• On error returns false plus the error value; the coroutine is then dead.
• Resuming a dead coroutine returns false, "cannot resume dead coroutine".

local co = coroutine.create(function(a, b)
    local c = coroutine.yield(a + b)
    return c * 2
end)
print(coroutine.resume(co, 1, 2))
print(coroutine.resume(co, 10))

coroutine.running(): thread | nil

coroutine.running(): thread | nil

• Returns the running coroutine, or nil when called from the main thread (Lua 5.1 semantics).

coroutine.status(co: thread): string

coroutine.status(co: thread): string

• Returns "running" if co is the running coroutine, "suspended" if it has yielded or not started, "normal" if it is active but has resumed another coroutine, and "dead" if it finished or failed.

coroutine.wrap(f: function): function

coroutine.wrap(f: function): function

• Creates a coroutine like create and returns a function that resumes it each time it is called.
• Arguments of the call are passed to resume; returned values are the values yielded or returned.
• Errors are propagated to the caller instead of being returned.

local gen = coroutine.wrap(function()
    for i = 1, 3 do coroutine.yield(i) end
end)
print(gen(), gen(), gen())

coroutine.yield(...: any): any

coroutine.yield(...: any): any

• Suspends the running coroutine. The arguments become extra results of the resume that started this run.
• Returns the arguments passed to the next resume.
• Errors if called outside a coroutine.