function traceback ()
	local level = 1
	while true do
		local info = debug.getinfo(level, "Sl")
		if not info then break end
		if info.what == "C" then		-- is a C function?
			print(level, "C function")
		else	-- a Lua function
			print(string.format("[%s]:%d",
					info.short_src, info.currentline))
		end
		level = level + 1
	end
end

ap.rputs(debug.traceback())
ap.status(ap.OK)
print(debug.traceback())