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Credit to MBoffin who inspired me to write this, mostly so I myself could prove that I understood seldom used Pico-8 command set of COROUTINES such as COCREATE(), CORESUME(), and YIELD().

Cart #cocreate_demo-0 | 2019-09-19 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA
3

If you just want the source without the sound effects, that can be found HERE:

 
-- dw817's very simple
-- cocreate() program

function main() ------------->>

cls()

init=0

repeat

-- if press (x) or this is the
-- first time to run,
-- prepare for being able to
-- call function "act" as a
-- co-creation
if btnp(5) or init==0 then
  init=1

-- make a pointer for the
-- cocreation function "act"
  go=cocreate(act)
  sfx(0) -- low pitch
end

-- if press (o) then call
-- routine here to plot three
-- circles, one at a time, and
-- one for each press
if btnp(4) then
  coresume(go)
end

-- update screen
flip()

until forever
end --<<-----------------------

-- three circles, click (o)
-- three times to see all three
function act()
  circfill(10,10,10,5)
  sfx(1) -- high pitch

-- each time yield is used,
-- the position of where the
-- program is in the function
-- is recorded and the function
-- exits
  yield()

-- the second time you press
-- (o) the function will start
-- here, not at the beginning
  circfill(20,10,10,6)
  sfx(1) -- high pitch
  yield()

-- as above, this function
-- starts here on a 3rd press
  circfill(30,10,10,7)
  sfx(1) -- high pitch
  yield()

-- there is nothing more here
-- so pressing (o) a 4th or
-- more does nothing.
-- you must call cocreate()
-- again in order to reset
-- this function to start
-- running the 3-circles again
end

main()

HOPE THIS HELPS !

3
1

You are missing the key aspect: local variable state is preserved on yield.
(the whole function state is preserved actually)
Allows things like:

 
local j=5
for i=1,30 do
 j+=2*i
 print(j)
 yield()
end


You would think it would. It wouldn't be very useful if it didn't. :) And yes, I should write code to reflect that. Wasn't thinking at the time.

Still would be a lot easier if you could use YIELD() in any function without having to create an additional variable, and can use something like RESET(Function) to reset the pointer position in it.

This is a very helpful and simple example, thanks!

You're very welcome, hwd2002. This code is new to me too. :)

Let me see if I can find an application where the variables in it could be recalled for further use. Now if it could do a true loop and never lose its local variables, that might be useful.



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