Handling ambiguous uppercase/lowercase dotted 'İ / i' and undotted 'I / ı' in Turkish language

[alisafaya]

I noticed that Julia doesn't contain a functionality that can handle localized string manipulation. For example uppercase and lowercase functions cannot be used with locales like tr_TR.

julia> turkish_text = "istanbul";
julia> uppercase(turkish_text)
"ISTANBUL"

ISTANBUL is not the right uppercase of istanbul in Turkish, it has to be İSTANBUL

Same goes for lowercase function

julia> turkish_text = "ISPARTA";
julia> lowercase(turkish_text)
"isparta"

Again, isparta is not the right lowercase of ISPARTA in Turkish, it has to be ısparta.

I am sure there are some other examples from other languages. I hope you can add this to the next versions of Julia.

Thanks!

[kimikage]

cf. #19516

[JeffBezanson]

One thing to do here would be to bring back https://github.com/JuliaStrings/ICU.jl. The design of the C locale system is really not good, and we want to avoid changing the behavior of functions based on locale whenever possible. But it would be great to have this function available in a package.