Re: Lua 5.2 - emulation of old setfenv

["Thomas Harning Jr." <harningt@...>]

On Thu, Jan 6, 2011 at 2:21 AM, HyperHacker <hyperhacker@gmail.com> wrote:
> On Thu, Jan 6, 2011 at 00:17, Dirk Laurie <dpl@sun.ac.za> wrote:
>> On Thu, Jan 06, 2011 at 07:56:58AM +0200, Miles Bader wrote:
>>> Lorenzo Donati <lorenzodonatibz@interfree.it> writes:
>>> First step: what's the best way to detect one is running in 5.2?
>>>
>>> I can do:
>>>
>>>    local lua_52 = string.match(_VERSION, " 5[.]2$")
>>>
>>> but my impression is that such version-string matching is often thought
>>> of as being not-so-good (e.g., the above will fail in 5.3 or 6.0, even
>>> though they're likely to be more like 5.2 than 5.1).
>>
>> local lua_version = tonumber(string.match(_VERSION,'%d*%.%d*'))
>>
>> will allow the test
>>
>>    if lua_version >= tonumber('5.2') then -- etc
>>
>> Dirk
>>
>>
>>
>
> I had been wondering why aside from _VERSION there isn't some variable
> with the numeric version number for this purpose.
Perhaps a major/minor variable would be good to have... converting 5.2
to a number will work until they come out with version 5.10 (depending
on how they do versions...)... fell into that hole when working with
LPeg and doing version management.

Perhaps the best way to work with versions is to do feature detection
by the presence/non-presence of functions/variables.  The danger in
this is if a function's "signature" or behavior changes, though it
seems this has been rare for the core Lua functionality.

-- 
Thomas Harning Jr.