Supporting \BCPdata{language}

[projetmbc]

Hello.

AFAI, siunitx does not support the very useful \BCPdata{language} which allows knowing the main language from the babel point of view. Of course, we still need access to a manual choice of language for siunitx if, for example, babel is not used.

What do you think about that?

[josephwright]

siunitx supports setting locale but that is not really language - it's intended for the location of publication and thus prevailing typesetting conventions, which are not necessarily tied to language. As such, using the BCP data would be tricky: you could extract say UK from en-UK, but you'd never get fr-UK but could be typesetting a book in French but using UK conventions. So I'm not sure this would fit the siunitx model (that language and typesetting conventions should be tracked independently).

[projetmbc]

There is a default loading of Anglo-Saxon settings, so why can't we have a standard automatic setting like fr-FR guessed using the BCP data?
In any case, since the use of fr-UK is not standard and requires action on the part of the user, my proposal won't require any new more user work.

[josephwright]

I'm waiting on an addition to expl3 which may help here - may be able to revisit shortly.

[projetmbc]

Just out of curiosity. What is this addition?

[josephwright]

@projetmbc latex3/latex3#1846