Re: Next Version of Lua?

[David Given <dg@...>]

Robert Raschke wrote:
[...]
> If I remember correctly, Lua optimises tail calls. In my experience, 
> using tail calls for state transitions is way easier to understand and 
> code than using goto's. But YMMV, I guess.

Tail calls don't let you easily share state using local variables --- 
you either have to pass all your state in using parameters, or else put 
the whole thing inside a bigger function and use upvalues. Either way, 
it's significantly more heavyweight. Still fast (I posted some 
benchmarks a little while ago), but considerably less so than a simple 
jump from one bytecode location to another.

> Or is your problem, that you've already got lots of machine generated 
> goto-state machines that you'd like to "translate" to Lua?

This is my major use case, yes, but it'd also be useful in other places. 
Consider this --- most languages provide some sanitised goto to handle 
doing this sort of thing:

while a do
  while b do
    while c do
      while d do
        if abort() then
          goto exitloopc
        endif
      end
    end
    exitloopc:
  end
end

--
David Given
dg@cowlark.com