Say no to global by default?

[Gavin Wraith <gavin@...>]

I have not read all the correspondence on the
"Say no to globals by default thread" so it could be that
this is redundant. In the latest version of RiscLua I
have a prelude containing:

local D = { }
global = setmetatable ({ }, {
    __newindex = function (t, n, v) rawset (_G, n, v) end,
    __index = rawget,
    })
global ._PROMPT = "> "
setmetatable (_G, {
  __newindex = function (t, n, v)
  if not D[n] then
    local w = debug.getinfo (2, "S").what
    if w ~= "C" then
      error ("\nattempt to write to undeclared variable " .. n, 2)
    end -- if
    D[n] = true
  end -- if
  rawset (t, n, v)
 end ,
 __index = function (_, n)
      if not D[n] then
       error ("\nattempt to read undeclared variable " .. n, 2)
      end -- if
  end,
} )

So the first assignment to a global variable x
has to be

   global.x = foo

but before that any reference to x raises an error.
--
Gavin Wraith (gavin@wra1th.plus.com)
Home page: http://www.wra1th.plus.com/