Re: finite state machine in lua

[Sean Conner <sean@...>]

It was thus said that the Great Srinivas Murthy once stated:
> Last discussion in this archive is very old hence wanted to check.
> I need to implement a finite-state-machine in lua. Please let me know if
> http://lua-users.org/wiki/FiniteStateMachine is still the right way to go
> if I should use some libs. If so which one.
> 
> Thanks

  Personally, I tend to use mutually recursive functions to handle state
machines in Lua.  Since Lua has tall calls, stack overflows are not an
issue.

	function state1(state)
	  local event = getevent(state)
	  if event  == ACTION1 then
	    return state2(state)
	  elseif event == ACTION2 then
	    return state3(state)
	  else
	    return state1(state)
	  end
	end

	function state2(state)
	  local event = getevent(state)
	  if event == ACTION3 then
	    return state1(state)
	  elseif event == ACTION4 then
	    return state3(state)
	  else
	    return state2(state)
	  end
	end

	function state3(state)
	  local event = getevent(state)
	  if event == QUIT then
	    return -- this leaves the state machine entirely
	  elseif event == ACTION1 then
	    return state1(state)
	  elseif event == ACTION2 then
	    return state2(state)
	  else
	    return state3(state)
	  end
	end

  I've used this method to implement TFTP, using the same state machine for
client and server, but starting in a different state depending upon which
side it was.

  -spc