Re: Lua and backwards compatibility - was Re: [ANN] Lua 5.3.4 (rc2) now available,

[Russell Haley <russ.haley@...>]

That's what I was thinking! Add it as a source package and compile one binary for those that need it its and share state between them. Also add a loader function that calls openssl so we can have encrypted files. 

Russ

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  Original Message  
From: Soni L.
Sent: Friday, January 13, 2017 6:08 AM
To: Lua mailing list
Reply To: Lua mailing list
Subject: Re: Lua and backwards compatibility - was Re: [ANN] Lua 5.3.4 (rc2) now available,



On 13/01/17 12:00 PM, Soni L. wrote:
>
>
> On 13/01/17 08:27 AM, Dibyendu Majumdar wrote:
>> On 13 January 2017 at 09:52, Daurnimator <quae@daurnimator.com> wrote:
>>> On 13 January 2017 at 20:01, steve donovan 
>>> <steve.j.donovan@gmail.com> wrote:
>>>> On Fri, Jan 13, 2017 at 9:43 AM, Dirk Laurie 
>>>> <dirk.laurie@gmail.com> wrote:
>>>>> Isn't it possible to mimic setfenv and getfenv (inefficiently) in
>>>>> "pure" Lua 5.3 via the debug library?
>>>> Well, naturally but the documentation also warns that the debug
>>>> library can be very slow.
>>>>
>>>> _ENV never freaked me out because I never use it ;) And never missed
>>>> setfenv either.
>>> _ENV can be a bit weird to get used to, but once you start using it
>>> you start to come up with nice new patterns/idioms.
>>>
>>> However the reason I don't use _ENV more often is I often have to end
>>> up writing code with lua 5.1 compatibility.
>>>
>> In Ravi I would like to add support for 5.1 and 5.2 backward
>> compatibility. Has anyone implemented the missing features of 5.1 in
>> 5.3 that I can look at?
>>
>> I have no experience with 5.1 and do not know how setfenv/getfenv ad
>> related C api functions should be implemented, but I would like to add
>> these to Ravi.
>>
>> Thanks and Regards
>> Dibyendu
>>
>
> I did some thinking on it a while back, but I can't recall what I came 
> up with...
>
> I *think* I talked about it somewhere on my github[1], maybe on the 
> SExLua repo[2], but yeah idk.
>
> (Or maybe it was on this list, scattered across multiple threads...)
>
> Just make every function have an _ENV, whether it uses globals or not. 
> Then basically upvaluejoin when setfenv and return it when getfenv - 
> don't bother with temporary in-function environments, since those are 
> not *the* function's environment.
>
> [1] https://github.com/SoniEx2/
> [2] https://github.com/SoniEx2/sexlua
>

PS: I personally like the idea of having multiple compilers (one for 
5.1, one for 5.2, one for 5.3) for the same VM, since there were library 
semantic changes between 5.1/5.2/5.3 and those aren't easy to autodetect 
while also supporting multiple lua versions. Then invoke their stdlib 
with require"5.1" and call .load(5.1 code) and the 5.1 code gets loaded 
1. with the right stdlib 2. with the right operator/etc semantics

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