YEng "live runner" (watching and reloading the script file as it's edited)

liverun_opengl_test.lua

if not _init then -- nice hack to prevent us from reopening the window every time, note the globals here
  _init=true
  _window=Y.sdl.quickGL("liverun opengl test")
end
-- alternatively, when reopening the window, don't forget to Y.sdl.closeWindow(_window) before, or you'll get spammed with orphaned windows.

while true do
  Y.sdl.pumpEvents()
  Y.gl.ClearColor( 0, 1, 1, 1 ) -- change this color to see it updated on the fly.
  Y.gl.Clear(Y.gl.COLOR_BUFFER_BIT)
  Y.sdl.gL_SwapWindow(_window)
  Y.sdl.delay(1)
end

liverun_strobe_test.moon

import random from math
export _init,_window

if not _init
  _init=true
  _window=Y.sdl.quickGL "strobe test"
  Y.sdl.gL_SetSwapInterval 1


with Y
  while true
    .sdl.pumpEvents!
    with Y.gl
      .ClearColor random(0,1), random(0,1), random(0,1), 1
      .Clear .COLOR_BUFFER_BIT
    with Y.sdl
      .gL_SwapWindow _window
      .delay 1

YEng_liverun.lua

require 'YEng'

local loadfile=loadfile
local filepath=arg[1]
if filepath=="-m" then
  loadfile=require "moonscript.base".loadfile
  filepath=arg[2]
end

do
  assert(type(filepath)=="string",'arg missing.\n\nUsage:\n./lj liverun.lua some_file.lua\n./lj liverun.lua -m some_file.moon\n')
  assert(io.open(filepath,'r'),'File "'..filepath..'" can not be opened for reading.')
  local fileage=0
  local function watch()
    if lfs.attributes(filepath,'modification') ~= fileage then
      error("reload")
    end
  end
  local function cycle()
    fileage=lfs.attributes(filepath,'modification')
    local filefun,err=loadfile(filepath)
    if not filefun then print(err) end
    local ret=xpcall(function()
      debug.sethook(watch, "count", 1)
      filefun()
      debug.sethook()
      return true
    end,function(...)
      debug.sethook()
      print(debug.traceback(...))
      return nil
    end)
    debug.sethook()
    return ret
  end
  while not cycle() do
    Y.sleep(0.5)
  end
  print("done.")
end