Merge 2023-06 LWG Motion 4

P2587R3 to_string or not to_string

Author: tkoeppe

source/compatibility.tex

@@ -31,6 +31,24 @@
 bool b = ne({2,3}, {1,2,3}); // unspecified result; previously \tcode{false}
 \end{example}
 
+\rSec2[diff.cpp23.strings]{\ref{strings}: strings library}
+
+\diffref{string.conversions}
+\change
+Output of floating-point overloads of \tcode{to_string} and \tcode{to_wstring}.
+\rationale
+Prevent loss of information and improve consistency with other formatting
+facilities.
+\effect
+\tcode{to_string} and \tcode{to_wstring} function calls that take
+floating-point arguments may produce a different output.
+For example:
+\begin{codeblock}
+auto s = std::to_string(1e-7);  // \tcode{"1e-07"}
+                                // previously \tcode{"0.000000"} with \tcode{'.'} possibly
+                                // changed according to the global C locale
+\end{codeblock}
+
 \rSec1[diff.cpp20]{\Cpp{} and ISO \CppXX{}}
 
 \rSec2[diff.cpp20.general]{General}

source/strings.tex

@@ -5196,18 +5196,7 @@
 \begin{itemdescr}
 \pnum
 \returns
-Each function returns a \tcode{string} object holding the character
-representation of the value of its argument that would be generated by calling
-\tcode{sprintf(buf, fmt, val)} with a format specifier of
-\tcode{"\%d"},
-\tcode{"\%u"},
-\tcode{"\%ld"},
-\tcode{"\%lu"},
-\tcode{"\%lld"},  \tcode{"\%llu"},
-\tcode{"\%f"},
-\tcode{"\%f"},
-or \tcode{"\%Lf"}, respectively, where \tcode{buf} designates an internal
-character buffer of sufficient size.
+\tcode{format("\{\}", val)}.
 \end{itemdescr}
 
 \indexlibraryglobal{stoi}%
@@ -5294,19 +5283,7 @@
 \begin{itemdescr}
 \pnum
 \returns
-Each function returns a \tcode{wstring} object holding the character
-representation of the value of its argument that would be generated by calling
-\tcode{swprintf(buf, buffsz, fmt, val)} with a format specifier of
-\tcode{L"\%d"},
-\tcode{L"\%u"},
-\tcode{L"\%ld"},
-\tcode{L"\%lu"},
-\tcode{L"\%lld"},
-\tcode{L"\%llu"},
-\tcode{L"\%f"},
-\tcode{L"\%f"},
-or \tcode{L"\%Lf"}, respectively, where \tcode{buf} designates an
-internal character buffer of sufficient size \tcode{buffsz}.
+\tcode{format(L"\{\}", val)}.
 \end{itemdescr}
 
 \rSec2[basic.string.hash]{Hash support}

source/support.tex

@@ -736,6 +736,7 @@
 #define @\defnlibxname{cpp_lib_to_address}@                        201711L // also in \libheader{memory}
 #define @\defnlibxname{cpp_lib_to_array}@                          201907L // also in \libheader{array}
 #define @\defnlibxname{cpp_lib_to_chars}@                          202306L // also in \libheader{charconv}
+#define @\defnlibxname{cpp_lib_to_string}@                         202306L // also in \libheader{string}
 #define @\defnlibxname{cpp_lib_to_underlying}@                     202102L // also in \libheader{utility}
 #define @\defnlibxname{cpp_lib_transformation_trait_aliases}@      201304L // also in \libheader{type_traits}
 #define @\defnlibxname{cpp_lib_transparent_operators}@             201510L // also in \libheader{memory}, \libheader{functional}