From: Bruno Haible <bruno@clisp.org>
To: emacs-devel@gnu.org
Cc: Sam Steingold <sds@gnu.org>
Subject: Re: case-insensitive string comparison
Date: Mon, 25 Jul 2022 21:37:16 +0200 [thread overview]
Message-ID: <2837483.e9J7NaK4W3@nimes> (raw)
In-Reply-To: <lz1qu92rvh.fsf@3c22fb11fdab.ant.amazon.com>
Sam Steingold asked:
> > (string-collate-equalp "a" "A" current-locale-environment t)
> > ==> nil
> > current-locale-environment
> > ==> "en_US.UTF-8"
>
> So, how do we do case-insensitive string comparison in Emacs?
>
> It is okay to add a `string-equal-ignore-case' based on `compare-strings'?
> (even though it does not recognize "SS" and "ß" as equal)
>
> Or should we first implement something like casefold in Python?
> https://docs.python.org/3/library/stdtypes.html#str.casefold
The Unicode Standard's algorithm for case-insensitive string comparison
is indeed much better thought-out than anything that you could come
up with within a month.
You are pointing to the Python implementation. But there's also an
implementation in GNU libunistring [1] and one in ICU4C <unicode/ustring.h>
[2]. Emacs could surely use one of these.
The implementation from GNU libunistring is also available through Gnulib,
as a set of modules [3]. The most relevant modules are
unicase/u8-casecmp
unicase/u8-casecoll
unicase/u8-casefold
unicase/u8-casemap
unicase/u8-casexfrm
unicase/u8-ct-casefold
unicase/u8-ct-tolower
unicase/u8-ct-totitle
unicase/u8-ct-toupper
Bruno
[1] https://www.gnu.org/software/libunistring/manual/html_node/Case-insensitive-comparison.html
[2] https://unicode-org.github.io/icu/userguide/transforms/casemappings.html
[3] https://www.gnu.org/software/gnulib/MODULES.html
next prev parent reply other threads:[~2022-07-25 19:37 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-19 17:27 case-insensitive string comparison Sam Steingold
2022-07-19 18:06 ` Mattias Engdegård
2022-07-19 18:56 ` Sam Steingold
2022-07-20 4:39 ` tomas
2022-07-20 11:35 ` Eli Zaretskii
2022-07-20 13:30 ` tomas
2022-07-19 18:16 ` Stefan Kangas
2022-07-19 19:39 ` Roland Winkler
2022-07-19 22:47 ` Sam Steingold
2022-07-20 2:21 ` Roland Winkler
2022-07-20 3:01 ` Stefan Monnier
2022-07-20 16:22 ` Sam Steingold
2022-07-25 14:23 ` Sam Steingold
2022-07-25 15:58 ` Eli Zaretskii
2022-07-25 19:39 ` Sam Steingold
2022-07-26 13:05 ` Eli Zaretskii
2022-07-26 14:16 ` Sam Steingold
2022-07-26 15:53 ` Eli Zaretskii
2022-07-26 16:00 ` Sam Steingold
2022-07-26 16:16 ` Lars Ingebrigtsen
2022-07-26 14:43 ` Robert Pluim
2022-07-25 19:37 ` Bruno Haible [this message]
2022-07-26 3:24 ` Richard Stallman
2022-07-26 8:00 ` Helmut Eller
2022-07-26 12:21 ` Eli Zaretskii
2022-07-27 2:58 ` Richard Stallman
2022-07-31 8:24 ` Eli Zaretskii
2022-07-26 14:28 ` Sam Steingold
2022-07-26 15:42 ` Sam Steingold
2022-07-26 16:10 ` Eli Zaretskii
2022-07-26 18:56 ` Bruno Haible
2022-07-26 19:30 ` Eli Zaretskii
2022-07-20 16:24 ` Roland Winkler
2022-07-20 17:06 ` Sam Steingold
2022-07-20 17:16 ` Eli Zaretskii
2022-07-20 17:12 ` Eli Zaretskii
2022-07-20 17:37 ` Roland Winkler
2022-07-20 17:50 ` Eli Zaretskii
2022-07-20 18:10 ` Roland Winkler
2022-07-20 18:16 ` Eli Zaretskii
2022-07-20 18:18 ` [External] : " Drew Adams
2022-07-21 6:56 ` Eli Zaretskii
2022-07-21 14:19 ` Roland Winkler
2022-07-21 15:53 ` Eli Zaretskii
2022-07-21 16:35 ` Roland Winkler
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