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On 6/2/06, Jérôme VUARAND <> wrote:
t = {}
setmetatable(t, {
  __newindex = function(self, key, value)
    print("Hello World! ("..key..value..")")

t["foo"] = "bar"
> Hello World! (foobar)

There is a strong distinction between variables and values in Lua.
Variables are merely references to values. In :
t = "foo"
you are not affecting a value to the above table, you are affecting a
new value to an untyped variable (t). But you cannot set metatable for
variables, only for values. That's a good reason for not having a kind
of __reference or __copy metamethod.

The __reference metamethod would not operate on variable t, but rather on the
value, which is going to be assigned to this variable. like:

t = {}
setmetatable(t, {
 __ref = function(table)
  return table
}) <- the normal behaviour

setmetatable(t, {
 __ref = function(table)
   local tmp = {}
   for i, j in pairs(table) do
     tmp[i] = j
   return tmp
}) <- make "=" behave like copy.

2006/6/1, Alexey Zaytsev <>:
> Hello.
> Is it possible to redefine the reference ("=") operator for tables in lua?
> I thougth it is a job for metamethods, but could not find any. Is
> there any reason for not having any __reference (or __copy) metamethod
> in lua?