Re: global environment special case

["John Belmonte" <jvb@...>]

> By making this change the Lua language and documentation would be
> simplified, and I believe the complexity of implementing extensions would
be
> reduced.

Recently I did a test to determine how the "global environment as a table"
change would affect an extension.  I re-implemented my function overloading
extension to operate on tables instead of the global environment, and added
an init function that applies it to any table given its tag number:

  function overload_init( tagnum )
      settagmethod( tagnum, "settable", tm_settable )
      settagmethod( FuncRecTag, "function", tm_function )
  end

Given the change I proposed, the extension could now be used with both the
global environment and tables:

  overload_init( tag(globaltable()) )
  overload_init( tag(mytable) )

However there is an issue here that those experienced with Lua extensions
will quickly recognize.  The "settable" tagmethod cannot be set for tables
with a default tag.  So this raises some questions:

  What tag will the global table have by default?
  Can the global table's tag be changed?

I think this is getting at the heart of the difference between the
interfaces Lua presents to tables and the global environment.  In addition,
a related question might be this:

  Can the restrictions on tagmethods be loosened without significantly
affecting performance?


-John