From: Lars Ingebrigtsen <larsi@gnus.org>
To: Howard Melman <hmelman@gmail.com>
Cc: 51292@debbugs.gnu.org
Subject: bug#51292: 27.2; Reversing strings with unicode combining characters
Date: Tue, 19 Oct 2021 21:26:31 +0200 [thread overview]
Message-ID: <87fsswbyu0.fsf@gnus.org> (raw)
In-Reply-To: <2AC0A88D-4F2F-41A5-B945-8BB55260C0E8@gmail.com> (Howard Melman's message of "Tue, 19 Oct 2021 15:16:27 -0400")
Howard Melman <hmelman@gmail.com> writes:
> Reversing a string fails to account for unicode combining characters
>
> (reverse "nai\u0308ve")
> "ev̈ian"
>
> Note the diaeresis is now on the v and not the i. s-reverse gets it right:
>
> (s-reverse "nai\u0308ve")
> "evïan"
So I wondered what s-reverse did, and indeed:
(defun s-reverse (s)
"Return the reverse of S."
(declare (pure t) (side-effect-free t))
(save-match-data
(if (multibyte-string-p s)
(let ((input (string-to-list s))
output)
(require 'ucs-normalize)
(while input
;; Handle entire grapheme cluster as a single unit
(let ((grapheme (list (pop input))))
(while (memql (car input) ucs-normalize-combining-chars)
(push (pop input) grapheme))
(setq output (nconc (nreverse grapheme) output))))
(concat output))
(concat (nreverse (string-to-list s))))))
Emacs has string-reverse, obsolete since 25.1. Perhaps we should
reintroduce it and use the definition from s?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
next prev parent reply other threads:[~2021-10-19 19:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 19:16 bug#51292: 27.2; Reversing strings with unicode combining characters Howard Melman
2021-10-19 19:26 ` Lars Ingebrigtsen [this message]
2021-10-19 20:50 ` Lars Ingebrigtsen
2021-10-19 21:21 ` Howard Melman
2021-10-20 8:58 ` Lars Ingebrigtsen
2021-10-19 23:13 ` Stefan Kangas
2021-10-20 8:11 ` Lars Ingebrigtsen
2021-10-20 13:02 ` Stefan Kangas
2021-10-21 2:50 ` Lars Ingebrigtsen
2021-10-21 3:51 ` Stefan Kangas
2021-10-20 11:50 ` Eli Zaretskii
2021-10-20 11:45 ` Eli Zaretskii
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