I discovered Luvit about a month ago, and have become very excited about
the possibilities it holds. I had never used Lua before, but I am quickly
falling in love with its clean, minimalist design (what Javascript
could/should have been), and its coroutines. I've read a few posts on this
list discussing alternate ideas for an API that would break away from the
callback-hell of Node, and I wanted to see if it was possible to create an
API that would perfectly mimic synchronous operations, while still allowing
asynchronous parallelism and background work. Below is a minimal example
(that doesn't actually use Luvit itself):
callbacks = {}
function event_loop()
while (#callbacks > 0) do
time = os.time()
for i, v in ipairs(callbacks) do
if time >= v[1] then
table.remove(callbacks, i)
v[2]()
break
end
end
end
end
-- Callback style functions
function set_timeout(seconds, cb)
table.insert(callbacks, {os.time() + seconds, cb})
end
function load_name(cb)
set_timeout(3, function() cb("Bob") end)
end
-- Synchronous style functions
function pause(seconds)
local co = coroutine.running()
set_timeout(seconds, function()
assert(coroutine.resume(co))
end)
coroutine.yield()
end
function get_name()
local co = coroutine.running()
load_name(function(name)
assert(coroutine.resume(co, name))
end)
return coroutine.yield()
end
-- Parallelization functions
function spawn(func)
coroutine.wrap(func)()
end
function parallel(...)
local args = {...}
local done = 0
local co = coroutine.running()
function task_done()
done = done + 1
if done == #args then
assert(coroutine.resume(co))
end
end
for i, func in ipairs(args) do
coroutine.wrap(function()
func()
task_done()
end)()
end
coroutine.yield()
end
-- The main program itself
function main()
print("Hello main, pause 2")
pause(2)
print("Getting name...")
local name = get_name()
print("Name was " .. name)
parallel(function()
print("Parallel 1, pause 3")
pause(3)
print("Done parallel 1")
end,
function()
print("Parallel 2, pause 3")
pause(3)
print("Done parallel 2")
end)
print("Done parallel, in main")
spawn(function()
print("In spawn 1, pause for 5 seconds")
pause(5)
print("Done with spawn 1")
end)
spawn(function()
print("In spawn 2, pause for 5 seconds")
pause(5)
print("Done with spawn 2")
end)
print("Main pause 2")
pause(2)
print("Done main")
end
coroutine.wrap(main)()
event_loop()
This is little more than a proof of concept at the moment, but I thought it
might be useful in the API design discussion.
Thanks,
Connor McKay
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