BB's Guide to Coroutines

local function myFunc(arg1, arg2, arg3)
	--# Code here
	
	return "aReturnedString"
end

local myResult = myFunc(1, 2, 3)

local function myFunc(text)
	print(text)
	
	return "cabbage"
end

local myCoroutine = coroutine.create(myFunc)

local ok, result = coroutine.resume(myCoroutine, "Hello, world!")  --# Starts myFunc, passes it "Hello, world!", which gets written to the screen.

print(ok)      --# Prints "true" (indicating the coroutine executed without error).
print(result)  --# Prints "cabbage", as returned by myFunc.

local ok, result = coroutine.resume(myCoroutine, "Hello, world!")

print(ok)      --# Prints "false" (indicating a problem executing the coroutine).
print(result)  --# Prints "cannot resume dead coroutine" (the error generated)

local function myFunc()
	for i = 1, 10 do
		coroutine.yield(i)
	end
	
	return "done!"
end

local myCoroutine = coroutine.create(myFunc)

while coroutine.status(myCoroutine) ~= "dead" do
	local ok, result = coroutine.resume(myCoroutine)
	
	print(result)  --# First prints 1 through 10, then prints "done!"
end

local function multiply(input)
	while true do
		input = coroutine.yield(input * 2)
	end
end

local myCoroutine = coroutine.create(multiply)

local myNum, ok = 1

for i = 1, 5 do
	ok, myNum = coroutine.resume(myCoroutine, myNum)
	
	print(myNum)  --# 2, 4, 8, 16, 32
end

coroutine.resume(yourComputersCoroutine, "eventType", "eventParameter1", "eventParameter2", etc)

local redstoneTimer = os.startTimer(1)  --# Ready a timer to create an event one second from now.

while true do
	local myEvent = { os.pullEvent() }  --# myEvent[1] = eventType, myEvent[2] = first parameter, etc
	
	if myEvent[1] == "timer" and myEvent[2] == redstoneTimer then
		rs.setOutput("left", not rs.getOutput("left"))  --# Invert the redstone output on the computer's left side.
		
		redstoneTimer = os.startTimer(1)  --# Ready the next timer to expire in another second...
		
	elseif myEvent[1] == "mouse_click" and myEvent[3] == 20 and myEvent[4] == 10 then
		--# User clicked at column 20 by row 10, do something about that here...
		
	end
end

while true do
	turtle.forward()
	
	local sender, message = rednet.receive(1)
	--# Maybe do something with the message here.
end

local function turtleFunc()
	while true do
		turtle.forward()
	end
end

local turtleCoroutine = coroutine.create(turtleFunc)
coroutine.resume(turtleCoroutine)  --# The function needs no parameters for its first resume.

local function rednetFunc()
	while true do
		local sender, message = rednet.receive(1)
		--# Maybe do something with the message here.
	end
end

local rednetCoroutine = coroutine.create(rednetFunc)
coroutine.resume(rednetCoroutine)

while true do
	local myEvent = { os.pullEvent() }
	
	if myEvent[1] == "turtle_response" then
		coroutine.resume( turtleCoroutine, unpack( myEvent ) )  --# See http://www.lua.org/pil/5.1.html regarding unpack
	
	elseif myEvent[1] == "rednet_message" or myEvent[1] == "timer" then
		coroutine.resume( rednetCoroutine, unpack( myEvent ) )
	
	end
end

local function turtleFunc()
	while true do
		turtle.forward()
	end
end

local turtleCoroutine = coroutine.create(turtleFunc)
local ok, turtleFilter = coroutine.resume(turtleCoroutine)    --# We'll capture the event filter turtle.forward() passes us when it yields!

local function rednetFunc()
	while true do
		local sender, message = rednet.receive(1)
		--# Maybe do something with the message here.
	end
end

local rednetCoroutine = coroutine.create(rednetFunc)
local ok, rednetFilter = coroutine.resume(rednetCoroutine)

while true do
	local myEvent = { os.pullEvent() }
	
	if myEvent[1] == turtleFilter or not turtleFilter then     --# If the event matches the filter, or if there IS no filter, then...
		ok, turtleFilter = coroutine.resume( turtleCoroutine, unpack( myEvent ) )  --# resume the coroutine, and update the filter!
	
	elseif myEvent[1] == rednetFilter or not rednetFilter then
		ok, rednetFilter = coroutine.resume( rednetCoroutine, unpack( myEvent ) )
	
	end
end

local function turtleFunc()
	while true do
		turtle.forward()
	end
end

local function rednetFunc()
	while true do
		local sender, message = rednet.receive(1)
		--# Maybe do something with the message here.
	end
end

parallel.waitForAll(turtleFunc, rednetFunc)

local function funcThatNeedsAnArg(arg)
	print("funcThatNeedsAnArg was passed "..arg.." as an arg.")
end

local upvalue
local function funcThatProducesAValue()
	upvalue = 5
end

parallel.waitForAll(function() funcThatNeedsAnArg("hello") end, funcThatProducesAValue)

print("funcThatProducesAValue set its upvalue to "..upvalue)