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Feature #10002

String swapcase

Added by randy15 (Andreas Runk) over 2 years ago. Updated over 2 years ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:63475]

Description

Hi, the ruby version 2.1.2 has a problem with the .swapcase function and german letters.
E.g. "ä".swapcase does return "ä" but should be "Ä".


Related issues

Related to CommonRuby - Feature #10085: Add non-ASCII case conversion to String#upcase/downcase/swapcase/capitalize Open

History

#1 [ruby-core:63476] Updated by nobu (Nobuyoshi Nakada) over 2 years ago

  • Tracker changed from Bug to Feature

#2 [ruby-core:63479] Updated by matz (Yukihiro Matsumoto) over 2 years ago

The current implementation of case conversion methods in String class only understands ASCII characters.
We'd like to enhance it when possible. But we have to know how each character should be converted.
For example, how should we convert "ß" (eszett)?

Matz.

#3 [ruby-core:63480] Updated by naruse (Yui NARUSE) over 2 years ago

At this time, ffi-icu or twitter-text-rb is useful.

#4 [ruby-core:63481] Updated by davispuh (Dāvis Mosāns) over 2 years ago

It have been already figured out by Unicode Standard, so just have to implement it. Look at Default Case Algorithms in section 3.13 and Case Mappings in section 5.18. Mappings can be viewed in SpecialCasing.txt (and UnicodeData.txt) also CaseFolding.txt could be useful.

From there "ß" (LATIN SMALL LETTER SHARP S) in uppercase would be "SS" (LATIN CAPITAL LETTER S) and it's user's responsibility to know that generally they are not reversible.

Also useful to read Character Properties, Case Mappings & Names FAQ

#5 [ruby-core:63483] Updated by zzak (Zachary Scott) over 2 years ago

We should delegate to @emboss everytime we need to convert ß...

#6 [ruby-core:63517] Updated by shyouhei (Shyouhei Urabe) over 2 years ago

We are talking about swapcase, not folding. The "generally they are not reversible" you say is the difficulty we are facing here. Also as you cited CaseFolding.txt, you should have been aware of type T folding, which is impossible without locale information.

If you think you can implement it, please show us.

Dāvis Mosāns wrote:

It have been already figured out by Unicode Standard, so just have to implement it. Look at Default Case Algorithms in section 3.13 and Case Mappings in section 5.18. Mappings can be viewed in SpecialCasing.txt (and UnicodeData.txt) also CaseFolding.txt could be useful.

From there "ß" (LATIN SMALL LETTER SHARP S) in uppercase would be "SS" (LATIN CAPITAL LETTER S) and it's user's responsibility to know that generally they are not reversible.

Also useful to read Character Properties, Case Mappings & Names FAQ

#7 [ruby-core:63970] Updated by duerst (Martin Dürst) over 2 years ago

  • Related to Feature #10085: Add non-ASCII case conversion to String#upcase/downcase/swapcase/capitalize added

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