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Edgar Toernig wrote:

Powerful it may be, but with the complexity I dare to disagree ;-)
It's even more obscure than the previous global statement *g*
I don't agree that it's obscure. Anyway, now that Lua has banished tag methods, inspired from your Sol work, we have room for a little new complexity :-). Especially when it's useful. 


  1) You no longer have one "global" table but a lot of them.  The
     term "global" becomes a little bit strange.
It's not so bad. Instead of thinking of "global" to mean the outermost scope or a specific table, I think of it to mean the way I access the variable. In other words, global accesses are those to undeclared variables, and I may want to map such accesses to a certain table. If you insist that "global" must mean the very outer scope, why not also say that "local" should mean only the innermost scope? 


  2) The global-table is attached to Lua functions.  You are no longer
     able to switch to another "global" table.  You have to explicitely
     change each and every function (hard/impossible to do).
I don't quite follow the problem here. It's easy to group functions that you would like to share scope within a function or chunk. 


  3) It introduces a hard to track dynamic binding.  It's impossible to
     tell which object is accessed by an identifier.  The binding is
     done dynamically at a later point (even while a function is active).
It looks like a feature to me. Writing a chunk with exported variables as globals and then being able to control binding according to the application is very powerful. The old global statement was too static-- a problem, especially since Lua lack's a macro system. 


IMHO, even

  local val
  mod_table = {}
  function mod_table.foo(x) val=x end
  function mod_table.bar(x) print(val) end

is easier to understand than these global table tricks.
What you're not showing is bar calling foo (in other words, code with countless references to mod_table). You're neglecting that to prevent global name clashes and get the best performance, you have to make mod_table local and return it to the caller. 

Anway, nothing prevents you from continuing to write in that style.

-John


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