How to implement a stopwatch in Lua? - lua

Question

How would you make a stopwatch in Lua?

Answer 1

I don't know Codea at all I'm afraid and you will most likely find that there are functions provided by that library for gettime and sleep. However as a pure Lua option (with the proviso that you use luasocket) the following code implements an example that could be built on.
socket = require('socket')
-- Define the stop watch
local start_time
function start()
-- Start the stop watch
start_time = socket.gettime() - 3800
end
function seconds_ellapsed()
-- Return the number of seconds since the stop watch was started
return socket.gettime() - start_time
end
-- As an example run the stop watch indefinately
start()
while true do
-- Get the time ellapsed and convert it to hours, minutes and seconds
ellapsed = seconds_ellapsed()
hours = math.floor(ellapsed / 3600)
minutes = math.floor((ellapsed - (hours * 3600)) / 60)
seconds = math.floor((ellapsed - (hours * 3600) - (minutes * 60)))
-- Print the time ellapsed to the command line
print(hours .. 'h', minutes .. 'm', seconds .. 's')
-- Wait a second between each update
socket.sleep(1)
end
You could look to use os.clock also but Lua has no builtin mechanism for setting the thread to sleep for a period (which was required for my example so I choose to use luasocket). There is a useful article on possible approaches for implementing sleep in lua here: http://lua-users.org/wiki/SleepFunction

Answer 2

Here is a very basic stopwatch, it starts/resets when the user taps the screen. This example shows elapsed minutes and seconds. If you want to count milliseconds, you can use ElapsedTime instead of os.time() and compute the number of hours, minutes etc. yourself instead of os.date(). Also, I don't have my iPad so there may be a bug.
function setup()
fontSize(20)
background(100, 120, 160)
fill(255)
toggle_timer()
end
function toggle_timer()
timer_on = not timer_on
if timer_on then
start = os.time()
end
end
function draw()
if timer_on then
text(os.date("%M:%S", os.difftime(os.time(), start)),
WIDTH / 2, HEIGHT / 2)
end
end
function touched(touch)
if touch.state == BEGAN then
toggle_timer()
end
end