GNU bug report logs - #27270
display-raw-bytes-as-hex generates ambiguous output for Emacs strings

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Message #49 received at 27270 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: v.schneidermann <at> gmail.com, 27270 <at> debbugs.gnu.org,
 npostavs <at> users.sourceforge.net
Subject: Re: bug#27270: display-raw-bytes-as-hex generates ambiguous output
 for Emacs strings
Date: Sat, 10 Jun 2017 10:24:25 +0300

> Cc: npostavs <at> users.sourceforge.net, 27270 <at> debbugs.gnu.org,
>  v.schneidermann <at> gmail.com
> From: Paul Eggert <eggert <at> cs.ucla.edu>
> Date: Fri, 9 Jun 2017 16:44:46 -0700
> 
> The idea is to add a new \X escape for character constants and strings. This 
> escape would allow at most two hexadecimal digits, rather than the unlimited 
> number of digits that \x does. For example, the Lisp string "\XABC" would be 
> equivalent to the Lisp string "\xAB\ C", that is, it would be a two-character 
> string containing the character U+00AB LEFT POINTING GUILLEMET followed by the 
> character U+0043 LATIN CAPITAL LETTER C.

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?

> 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.

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