[ruby-core:107753] [Ruby master Bug#18590] String#downcase and CAPITAL LETTER I WITH DOT ABOVE

Issue #18590 has been updated by duerst (Martin Dürst).


mame (Yusuke Endoh) wrote in #note-9:

> I wanted to create a PR to fix the document, but I am unsure what document is the best reference for full case mapping. @duerst Could you please fix it? Or should we wait until the chart will be fixed?

The best reference is section 3.13 (Default Case Algorithms) of https://www.unicode.org/versions/latest/ch03.pdf. This is a lot of text, not as easy to understand as a table. But maybe this is better. People don't need a table, it's easy to create one with Ruby :-).
[Please not that this URI currently redirects to https://www.unicode.org/versions/Unicode14.0.0/ch03.pdf, but I still have to upgrade Ruby to Unicode 14.0.0; hope to be able to do this in the next couple weeks.]

----------------------------------------
Bug #18590: String#downcase and CAPITAL LETTER I WITH DOT ABOVE
https://bugs.ruby-lang.org/issues/18590#change-96678

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* Priority: Normal
* Assignee: duerst (Martin Dürst)
* ruby -v: 3.1.0p0
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Downcasing for "İ" character works in an unexpected way:

```ruby
'İ'.downcase
=> "i̇"
```

Expected result - downcasing should return "i". Instead, it returns small "i" and additional "dot" character:

```ruby
'İ'.downcase.chars
=> ["i", "̇"]
```

According to the standard Unicode case mapping character 'İ'(0130) maps to lowercased 'i' (0069).

```
0130;LATIN CAPITAL LETTER I WITH DOT ABOVE;Lu;0;L;0049 0307;;;;N;LATIN CAPITAL LETTER I DOT;;;0069;
```

https://www.unicode.org/Public/UCD/latest/ucd/UnicodeData.txt




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>