Feature #14055: String#casecmp should use Unicode folding

• Status: Rejected
• Assignee: -
• Target version: -

[rbjl (Jan Lelis)]

The following string and symbol methods are currently only ASCII aware:

• String#casecmp
• String#casecmp!
• Symbol#casecmp
• Symbol#casecmp!

For example:

"a".casecmp("A") #=> 0
"ä".casecmp("Ä") #=> 1

Now that Ruby has implemented case-folding (which is meant for comparing strings, see http://unicode.org/faq/casemap_charprop.html#2), it should be used when doing a casecmp on Unicode strings:

"Ä".downcase(:fold) == "ä" #=> true

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Rejected

Yes, we have unicode-aware case folding. But the problem is, because String#casecmp returns either -1, 0, or 1, we need to define a total ordering of strings in case-insensitive manner. It's pretty difficult (if not impossible).

If you are not interested in sorting strings but only for comparison, you can use String#casecmp? method (note the "?"). See also: https://bugs.ruby-lang.org/issues/12786

[nobu (Nobuyoshi Nakada)]

• Related to Feature #12786: String#casecmp? added

[rbjl (Jan Lelis)]

Thanks for the pointer!