hi, i'm loving picotron so far! i just wanted to report some issues using coroutines.

when using coroutine.resume, it can sometimes return early when the coroutine runs for a while due to how picotron does timeslicing. from reading head.lua, i learned that using coresume instead of coroutine.resume fixes this, which makes me think maybe coroutine.resume should be replaced with it. another more minor issue is that coresume only returns the first value of a multiple-value return/yield from the coroutine, and not any more.

here's a simple test case:

local function long_running_coroutine ()
  for i = 1, 100 do
    cls()
  end
  return 1, 2
end

function working ()
  local c = coroutine.create (long_running_coroutine)
  coresume (c)
  assert (coroutine.status(c) == 'dead', 'this works')
end

function not_working ()
  local c = coroutine.create (long_running_coroutine)
  coroutine.resume (c)
  assert (coroutine.status(c) == 'dead', 'this doesn\'t work')
end

function also_not_working ()
  local c = coroutine.create (long_running_coroutine)
  local a, b, c = coresume (c)
  assert (a)
  assert (b)
  assert (c, 'only one coroutine return value returned')
end

function _draw ()
  working ()
  not_working ()
  also_not_working ()
end

The code for coresume is inside /system/lib/head.lua at around line 1078. By the looks of it, coroutine.resume requires some extra care and the current function only returns 2 values. (assuming the first returned value is related to the status.) It would require the use of pack and unpack in order to return more values.

oh this makes sense! in pico-8, coresume returns true, data if everything was fine (data = what is yielded) and false, error otherwise