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- Subject: Re: __declared
- From: Paige DePol <lual@...>
- Date: Wed, 30 Oct 2013 16:41:57 -0700
I do not believe that is part of the Lua core. I could not find any reference to '__declared' in the lua-5.2.2 code base and a grep for just 'declared' only returns results that are comments. I also looked in my own environment table and could not find a '__declared' field.
Perhaps you have a patched Lua and/or some other module is creating the '__declared' key in your environment?
On Oct 30, 2013, at 4:17 PM, Jose Torre-Bueno <email@example.com> wrote:
> Poking about I discovered that the metatable for _G (or _ENV) has a table called __declared whose keys are the names of user defined objects and value is always true. This seems a useful thing for testing whether a function has been defined or a table exists.
> I am not aware of any documentation of this feature, __declared does not appear in the Lua 5.2 reference manual or in the index of PiL 3rd edition. Is this a documented feature of Lua? Can I rely on this in the future? Also do the __newindex and __index functions in the metatable do anything other than maintain __declared?
> I discovered this in the process of studying whether I could create a function that incremented a counter for every access of a function. I have in mind a function installed as the __index function of the metatable that would maintain a table similar to __declared except that it would increment a counter for the called function every time it was called. if this function ended by calling the preexisting __index function would that work without breaking Lua?
> Jose de la Torre-Bueno, Ph.D.
> Empowered Energy Solutions Inc.
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