Re: A tricky way to determine Lua version

[Thijs Schreijer <thijs@...>]

> On 29 Jun 2018, at 01:58, Coda Highland <chighland@gmail.com> wrote:
> 
> On Thu, Jun 28, 2018 at 2:37 PM, Egor Skriptunoff
> <egor.skriptunoff@gmail.com> wrote:
>> 
>> 
>> On Sat, May 21, 2016 at 8:18 AM, Egor Skriptunoff wrote:
>>> 
>>> 
>>> simple program that determines Lua version.
>>> 
>>> local f, t = function()return function()end end, {nil,
>>>   [false]  = 'Lua 5.1',
>>>   [true]   = 'Lua 5.2',
>>>   [1/'-0'] = 'Lua 5.3',
>>>   [1]      = 'LuaJIT' }
>>> local version = t[1] or t[1/0] or t[f()==f()]
>>> 
>>> The curious fact about this program is that it doesn't depend on anything
>>> that can be changed.
>> 
>> 
>> 
>> Here is an update of Lua version detector.
>> Support for 5.0 and 5.4 was added.
>> 
>> --[=[
>> local version = 'Lua 5.0'
>> --[[]=]
>> local n = '8'; repeat n = n*n until n == n*n
>> local t = {'Lua 5.1', nil,
>>  [-1/0] = 'Lua 5.2',
>>  [1/0]  = 'Lua 5.3',
>>  [2]    = 'LuaJIT'}
>> local version = t[2] or t[#'\z'] or t[n/'-0'] or 'Lua 5.4'
>> --]]
>> 
> 
> Useful, but sadly this doesn't help distinguish between patch levels.
> 
> /s/ Adam
> 

It also misses detection of LuaJIT’s 5.2 compatibility flag

Thijs