Testing for variant/version

[Peter Flynn]

On 09/04/2024 10:58, David Carlisle wrote:

> You can use
> \ExplSyntaxOn
> \str_compare:nNnTF {aaay} < {aaax} {yes} {no}
> \ExplSyntaxOff
> 
> The latex format has already tested which engine you are using and 
> resolved differences between the primitive name and/or supplied Lua 
> implementation where needed, so you don't need to load any packages
> or re-test or load another lua emulation.

Excellent, thank you. What version does this date from?

On 09/04/2024 11:27, Joseph Wright wrote:

> I see David has given a sensible approach. Just to note that the
> test above fails as XeTeX uses \XeTeXversion not \xetexversion. 

So I discovered :-)

> If you want to stick with a test, I would not mess about with
> testing engine but rather functionality (so check for 
> \pdfstrcmp/\strcmp/\directlua).

OK, thanks.

Peter