From 61b94514fc249fa89139ca71e85dea7bec9a39af Mon Sep 17 00:00:00 2001
From: Dawn Perchik <dawn@brightsidecomputing.com>
Date: Sat, 18 Feb 2023 19:44:20 -0800
Subject: [PATCH] P2713R1 Escaping improvements in std::format

The wording has been integrated with the changes from P2736R2 (CWG
Motion 8) according to the advise contained in that paper.

Fixes NB US 098, FR 134 (C++23 CD).
---
 source/utilities.tex | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/source/utilities.tex b/source/utilities.tex
index 683f0dc455..24c8414f45 100644
--- a/source/utilities.tex
+++ b/source/utilities.tex
@@ -15963,12 +15963,20 @@
 \begin{itemize}
 \item
 \placeholder{CE} is UTF-8, UTF-16, or UTF-32 and
-\placeholder{C} corresponds to either
-a Unicode scalar value whose Unicode property \tcode{General_Category}
-has a value in the groups \tcode{Separator} (\tcode{Z}) or \tcode{Other} (\tcode{C}) or to
-a Unicode scalar value with the Unicode property \tcode{Grapheme_Extend=Yes},
+\placeholder{C} corresponds to a Unicode scalar value
+whose Unicode property \tcode{General_Category} has a value in the groups
+\tcode{Separator} (\tcode{Z}) or \tcode{Other} (\tcode{C}),
 as described by \UAX{44} of the Unicode Standard, or
 
+\item
+\placeholder{CE} is UTF-8, UTF-16, or UTF-32 and
+\placeholder{C} corresponds to a Unicode scalar value
+with the Unicode property \tcode{Grapheme_Extend=Yes}
+as described by \UAX{44} of the Unicode Standard and
+\placeholder{C} is not immediately preceded in \placeholder{S} by
+a character \placeholder{P} appended to \placeholder{E}
+without translation to an escape sequence, or
+
 \item
 \placeholder{CE} is neither UTF-8, UTF-16, nor UTF-32 and
 \placeholder{C} is one of an implementation-defined set
@@ -16050,7 +16058,8 @@
 then \placeholder{C} is appended unchanged.
 \end{itemize}
 
-%% FIXME: Example is incomplete; s2 and s6 are missing below;
+%% FIXME: Example is incomplete; s2 and s6 from P2286R8
+%%        and s8 (which should be s9) from P2713R1 are missing below;
 %% FIXME: their Unicode characters are not available in our font (Latin Modern).
 \begin{example}
 \begin{codeblock}
@@ -16062,6 +16071,8 @@
 string s4 = format("[{:?}]", string("\0 \n \t \x02 \x1b", 9));
                                                     // \tcode{s4} has value: \tcode{["\textbackslash u\{0\} \textbackslash n \textbackslash t \textbackslash u\{2\} \textbackslash u\{1b\}"]}
 string s5 = format("[{:?}]", "\xc3\x28");           // invalid UTF-8, \tcode{s5} has value: \tcode{["\textbackslash x\{c3\}("]}
+string s7 = format("[{:?}]", "\u0301");             // \tcode{s7} has value: \tcode{["\u{301}"]}
+string s8 = format("[{:?}]", "\\\u0301");           // \tcode{s8} has value: \tcode{["\\\u{301}"]}
 \end{codeblock}
 \end{example}