./system_lib.lua

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-- System Functions -- 
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_UGGlobals = { } 
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_DynamicGlobals = { } 
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_ActiveTable = "" 
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-- Assign a value to global variable. Any nil-assignment raises an error.

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-- 
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function _CatchNilAssignment(t, k, v) 
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	if (v == nil) then 
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		error("attempted to initialize global variable '"..k.."' with nil value")

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	elseif (_ActiveTable ~= "") then 
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		rawset( _DynamicGlobals[ _ActiveTable ], k, v )

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	else 
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		rawset(t, k, v) 
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	end 
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end 
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-- Catch an attempt to write to an undefined global variable

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-- 
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function _CatchUndefinedGlobalWrite(t, k, v)

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	if (v == nil) then 
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		error("attempted to initialize global variable '"..k.."' with nil value")

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		return 
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	end 
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	for i, table in pairs( _DynamicGlobals ) do

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		local val = rawget( table, k ) 
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		if (val ~= nil) then 
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			rawset( table, k, v ) 
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			return 
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		end 
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	end 
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	error("attempted to write to undefined global variable '"..k.."'")

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end 
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-- Find a value in the Dynamic table since it's not in UGGlobals

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-- 
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function _GetDynamicGlobal( t, k ) 
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	for i, table in pairs( _DynamicGlobals ) do

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		local v = rawget( table, k ) 
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		if (v ~= nil) then 
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			return v 
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		end 
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	end 
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	error("attempted to read undefined global variable '"..k.."'")

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end 
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-- Find a value in any global space, return nil if not found

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-- 
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function _GetAnyGlobalSilent( k ) 
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	local v 
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```
	 
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	v = rawget( _UGGlobals, k ) 
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```
	 
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	if v ~= nil then 
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		return v 
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	end 
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```
	 
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	for i, table in pairs( _DynamicGlobals ) do

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		v = rawget( table, k ) 
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		if v ~= nil then 
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			return v 
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		end 
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	end 
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	return nil 
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end 
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-- Prepare to load a lua script into the dynamic table

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-- 
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function _PrepareForDynamicGlobals( filename )

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	_DynamicGlobals[ filename ] = { } 
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	_ActiveTable = filename 
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	setmetatable( _UGGlobals, {__index = _GetDynamicGlobal, __newindex = _CatchNilAssignment} )

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end 
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-- Callback for loading of dynamic table complete

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-- 
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function _DynamicGlobalsLoadComplete( )

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	_ActiveTable = "" 
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	setmetatable( _UGGlobals, {__index = _GetDynamicGlobal, __newindex = _CatchUndefinedGlobalWrite} )

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end 
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-- Unload a table of Dynamic globals 
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-- 
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function _UnloadDynamicGlobals( filename )

	rawset( _DynamicGlobals, filename, nil ) -- erase the entry from the table

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end 
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-- Delay execution for a certain amount of time

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-- 
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-- duration:	duration of delay, in seconds (if time_seconds <= 0, execution will delay for exactly one frame)

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-- 
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function delay(duration) 
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	if duration == nil then 
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		duration = 0 
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	end 
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	local elapsed_time = 0.0 
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	repeat 
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		thread_yield() 
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		elapsed_time = elapsed_time + get_frame_time()

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	until (elapsed_time >= duration) 
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end 
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```