From: Paul Eggert <eggert@cs.ucla.edu>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 27270@debbugs.gnu.org, v.schneidermann@gmail.com,
npostavs@users.sourceforge.net
Subject: bug#27270: display-raw-bytes-as-hex generates ambiguous output for Emacs strings
Date: Sat, 10 Jun 2017 17:04:40 -0700 [thread overview]
Message-ID: <a69c6508-4b01-d859-5ff8-5417659c6127@cs.ucla.edu> (raw)
In-Reply-To: <83h8zo71au.fsf@gnu.org>
On 06/10/2017 12:24 AM, Eli Zaretskii wrote:
> So your proposal would mean a change to the Lisp reader to support
> such escapes, right? If so, isn't such a change
> backward-incompatible?
Yes, but only in the sense that undocumented escapes evaluate to
themselves, e.g., "\F" is currently the same as "F" in Emacs Lisp
because there is no escape sequence \F currently defined for character
constants. But there's nothing new here, e.g., when we added "\N{...}"
last year we changed the interpretation of the formerly-undocumented \N
escape.
>> Also, display-raw-bytes-as-hex would cause raw bytes to be displayed with this
>> new X escape, rather than with with the x escape.
> It could only do that for codepoints below 256 decimal, so that
> limitation should be taken into account when deciding on the proposal.
Ouch, I hadn't thought of that.
Wait -- doesn't that mean that "display-raw-bytes-as-hex" is a
misleading name, because it affects the display not only of raw bytes,
but of other undisplayable characters? Shouldn't we change its name to
something more generic and more accurate, like "display-characters-as-hex"?
Anyway, to address the point you raised: how about a different idea? We
extend the existing \x syntax in strings so that \x{dddd} has the same
meaning as "\xdddd", except that the "}" terminates the escape. This
syntax is used by Perl and so is in the same family as \N{...}. We also
change display-raw-bytes-as-hex to use this new syntax when a character
is immediately followed by a hexadecimal digit. That way, most
characters are displayed as before, but my problematic example is
displayed as "x\x{90}5y", which is a good visual cue of the unusual
situation.
next prev parent reply other threads:[~2017-06-11 0:04 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-07 3:57 bug#27270: display-raw-bytes-as-hex generates ambiguous output for Emacs strings Paul Eggert
2017-06-07 5:17 ` Eli Zaretskii
2017-06-08 0:49 ` Paul Eggert
2017-06-08 1:07 ` npostavs
2017-06-08 15:20 ` Eli Zaretskii
2017-06-08 15:56 ` Paul Eggert
2017-06-08 16:11 ` Eli Zaretskii
2017-06-08 16:24 ` Paul Eggert
2017-06-08 18:59 ` Eli Zaretskii
2017-06-08 19:43 ` Paul Eggert
2017-06-08 19:56 ` Eli Zaretskii
2017-06-08 20:35 ` Paul Eggert
2017-06-09 6:00 ` Eli Zaretskii
2017-06-09 23:44 ` Paul Eggert
2017-06-10 7:24 ` Eli Zaretskii
2017-06-11 0:04 ` Paul Eggert [this message]
2017-06-11 14:48 ` Eli Zaretskii
2017-06-11 17:26 ` Paul Eggert
2017-09-02 13:25 ` Eli Zaretskii
2022-04-23 14:00 ` Lars Ingebrigtsen
2022-04-24 7:10 ` Paul Eggert
2022-04-24 9:56 ` Vasilij Schneidermann
2022-04-24 10:26 ` Andreas Schwab
2022-04-24 10:51 ` Vasilij Schneidermann
2022-04-24 11:01 ` Andreas Schwab
2022-04-24 11:29 ` Lars Ingebrigtsen
2022-04-24 22:46 ` Paul Eggert
2022-04-24 11:24 ` Lars Ingebrigtsen
2022-04-24 22:35 ` Paul Eggert
2022-04-25 7:40 ` Lars Ingebrigtsen
2022-04-25 16:49 ` Paul Eggert
2022-04-26 10:06 ` Lars Ingebrigtsen
2022-04-26 16:48 ` Paul Eggert
2022-04-27 12:13 ` Lars Ingebrigtsen
2022-04-27 17:21 ` Paul Eggert
2022-04-27 17:22 ` Lars Ingebrigtsen
2022-04-28 17:58 ` Paul Eggert
2017-06-10 22:52 ` npostavs
2017-06-11 0:10 ` Paul Eggert
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