Re: Confusion about environments in Lua 5.2

[Milind Gupta <milind.gupta@...>]

Thanks.

Milind

On Tue, Apr 8, 2014 at 9:26 PM, Philipp Janda <siffiejoe@gmx.net> wrote:

Am 09.04.2014 06:13 schröbte Milind Gupta:

I did the following:

print(_G)

table: 00C31B98

print(_ENV)

table: 00C31B98

print(_G._G)

table: 00C31B98

print(_ENV._G)

table: 00C31B98

print(_ENV._ENV)

nil

print(_G._ENV)

nil

`_ENV` is an upvalue not a global. So it isn't in the globals table referenced by `_ENV` or `_G` (which really is `_ENV._G`).

when I do print(_ENV) doesn't it access the variable _ENV._ENV? but
printing _ENV._ENV is nil. So does it mean when I access any other variable
aexcept _ENV it is accessed as _ENV.var?

No. The rule is simple. When you access a variable `x` you get the innermost local or upvalue with that name in scope, or as a last resort the global variable `_ENV.x` if there is none in scope.

   So this means that a running code cannot change its own environment as it
could do in Lua 5.1.

Sure it can:

    _ENV = {}

Milind

Philipp