P2372R3 Fixing locale handling in chrono formatters

In [time.zone.zonedtime.nonmembers], remove the separate
"Returns" item now that have "Effects: Equivalent to: return ..."

Author: jensmaurer

source/support.tex

@@ -609,7 +609,7 @@
 #define @\defnlibxname{cpp_lib_exchange_function}@                 201304L // also in \libheader{utility}
 #define @\defnlibxname{cpp_lib_execution}@                         201902L // also in \libheader{execution}
 #define @\defnlibxname{cpp_lib_filesystem}@                        201703L // also in \libheader{filesystem}
-#define @\defnlibxname{cpp_lib_format}@                            202106L // also in \libheader{format}
+#define @\defnlibxname{cpp_lib_format}@                            202110L // also in \libheader{format}
 #define @\defnlibxname{cpp_lib_gcd_lcm}@                           201606L // also in \libheader{numeric}
 #define @\defnlibxname{cpp_lib_generic_associative_lookup}@        201304L // also in \libheader{map}, \libheader{set}
 #define @\defnlibxname{cpp_lib_generic_unordered_lookup}@          201811L

source/time.tex

@@ -2703,9 +2703,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-auto const dp = floor<days>(tp);
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} {}"),
-                    year_month_day{dp}, hh_mm_ss{tp-dp});
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@("{:L%F %T}"), tp);
 \end{codeblock}
 
 \pnum
@@ -2901,7 +2899,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3107,7 +3105,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3270,7 +3268,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 
 \pnum
@@ -3393,7 +3391,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(@\placeholder{STATICALLY-WIDEN}@<charT>("{:%F %T}"), t);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%F %T}"), t);
 \end{codeblock}
 \end{itemdescr}
 
@@ -4469,7 +4467,7 @@
 Equivalent to:
 \begin{codeblock}
 return os << (m.ok() ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%b}"), m) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%b}"), m) :
   format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} is not a valid month"),
          static_cast<unsigned>(m)));
 \end{codeblock}
@@ -5196,7 +5194,7 @@
 Equivalent to:
 \begin{codeblock}
 return os << (wd.ok() ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%a}"), wd) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%a}"), wd) :
   format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{} is not a valid weekday"),
          static_cast<unsigned>(wd.wd_)));
 \end{codeblock}
@@ -5350,8 +5348,8 @@
 \begin{codeblock}
 auto i = wdi.index();
 return os << (i >= 1 && i <= 5 ?
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[{}]"), wdi.weekday(), i) :
-  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[{} is not a valid index]"),
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[{}]"), wdi.weekday(), i) :
+  format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[{} is not a valid index]"),
          wdi.weekday(), i));
 \end{codeblock}
 \end{itemdescr}
@@ -5453,7 +5451,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}[last]"), wdl.weekday());
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}[last]"), wdl.weekday());
 \end{codeblock}
 \end{itemdescr}
 
@@ -5580,7 +5578,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{}"),
                     md.month(), md.day());
 \end{codeblock}
 \end{itemdescr}
@@ -5717,7 +5715,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/last"), mdl.month());
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/last"), mdl.month());
 \end{codeblock}
 \end{itemdescr}
 
@@ -5830,7 +5828,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{:L}"),
                     mwd.month(), mwd.weekday_indexed());
 \end{codeblock}
 \end{itemdescr}
@@ -5946,7 +5944,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L}/{:L}"),
                     mwdl.month(), mwdl.weekday_last());
 \end{codeblock}
 \end{itemdescr}
@@ -6260,7 +6258,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}"),
                     ym.year(), ym.month());
 \end{codeblock}
 \end{itemdescr}
@@ -7119,7 +7117,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}"),
                     ymdl.year(), ymdl.month_day_last());
 \end{codeblock}
 \end{itemdescr}
@@ -7515,7 +7513,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}/{:L}"),
                     ymwd.year(), ymwd.month(), ymwd.weekday_indexed());
 \end{codeblock}
 \end{itemdescr}
@@ -7863,7 +7861,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{}/{}"),
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{}/{:L}/{:L}"),
                     ymwdl.year(), ymwdl.month(), ymwdl.weekday_last());
 \end{codeblock}
 \end{itemdescr}
@@ -8609,7 +8607,7 @@
 \effects
 Equivalent to:
 \begin{codeblock}
-return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:%T}"), hms);
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@<charT>("{:L%T}"), hms);
 \end{codeblock}
 
 \pnum
@@ -10086,14 +10084,10 @@
 \begin{itemdescr}
 \pnum
 \effects
-Streams
-the value returned from \tcode{t.get_local_time()}
-to \tcode{os}
-using the format \tcode{"\%F \%T \%Z"}.
-
-\pnum
-\returns
-\tcode{os}.
+Equivalent to:
+\begin{codeblock}
+return os << format(os.getloc(), @\placeholder{STATICALLY-WIDEN}@("{:L%F %T %Z}"), t);
+\end{codeblock}
 \end{itemdescr}
 
 \rSec2[time.zone.leap]{Class \tcode{leap_second}}
@@ -10432,7 +10426,7 @@
 
 \begin{ncbnf}
 \fmtnontermdef{chrono-format-spec}\br
-    \opt{fill-and-align} \opt{width} \opt{precision} \opt{chrono-specs}
+    \opt{fill-and-align} \opt{width} \opt{precision} \opt{\terminal{L}} \opt{chrono-specs}
 \end{ncbnf}
 
 \begin{ncbnf}
@@ -10481,15 +10475,26 @@
 represented by \fmtgrammarterm{literal-char}
 are copied unchanged to the output.
 
+\pnum
+A \defnadj{formatting}{locale} is an instance of \tcode{locale}
+used by a formatting function, that is determined as follows:
+\begin{itemize}
+\item
+the "C" locale if the \tcode{L} option
+is not present in \fmtgrammarterm{chrono-format-spec}, otherwise
+\item
+the locale passed to the formatting function if any, otherwise
+\item
+the global locale.
+\end{itemize}
+
 \pnum
 Each conversion specifier \fmtgrammarterm{conversion-spec}
 is replaced by appropriate characters
 as described in \tref{time.format.spec};
 the formats specified in ISO 8601:2004 shall be used where so described.
 Some of the conversion specifiers
-depend on the locale that is passed to the formatting function
-if the latter takes one,
-or the global locale otherwise.
+depend on the formatting locale.
 If the formatted object does not contain the information
 the conversion specifier refers to,
 an exception of type \tcode{format_error} is thrown.
@@ -10764,6 +10769,7 @@
 If the \fmtgrammarterm{chrono-specs} is omitted,
 the chrono object is formatted
 as if by streaming it to \tcode{std::ostringstream os}
+with the formatting locale imbued
 and copying \tcode{os.str()} through the output iterator of the context
 with additional padding and adjustments as specified by the format specifiers.
 \begin{example}