Re: Why do we have ipairs?

[Sean Conner <sean@...>]

It was thus said that the Great William Ahern once stated:
> 
> What about label references? That is, if Lua allowed directly taking a
> reference to a label? Then you could use them directly, as when writing a
> classic state machine, or build your own jump tables which mapped keys to
> labels. Although you might have to add an optimization to memoize constant
> tables in the latter case.
> 
> The label reference would have to be a new native type. But it might be a
> little more elegant at the syntax level.
> 
> State machine example

  For state machines, you can use functions, because Lua supports tail call
optimizations, which are essentially gotos.  I implemented TFTP using that
method:

	local read_data
	local send_data
	local receive_ack
	local receive_data
	local write_data
	local send_ack

	read_data    = function() return send_data()    end -- [1]
	send_data    = function() return receive_ack()  end
	receive_ack  = function() return read_data()    end

	receive_data = fucntion() return write_data()   end
	write_data   = function() return send_ack()     end
	send_ack     = function() return receive_data() end

  Both the client and the server can use the same state machine---where they
start depends on who is sending the data, and who is receiving the data.

  -spc (I like this much better than using a switch or goto statements)

[1]	Obviously this is just a sample of the code.  There's a bit more
	to it, like error checking, resending, etc.