Merge 2024-03 LWG Motion 1

P3180R0 C++ Standard Library Issues to be moved in Tokyo, Mar. 2024

Author: tkoeppe

source/algorithms.tex

@@ -10773,11 +10773,9 @@
 \rSec3[numeric.sat.func]{Arithmetic functions}
 
 \pnum
-\begin{note}
 In the following descriptions, an arithmetic operation
 is performed as a mathematical operation with infinite range and then
 it is determined whether the mathematical result fits into the result type.
-\end{note}
 
 \indexlibraryglobal{add_sat}%
 \begin{itemdecl}

source/containers.tex

@@ -18837,8 +18837,12 @@
 \tcode{idx < size()} is \tcode{true}.
 
 \pnum
-\effects
-Equivalent to: \tcode{return *(data() + idx);}
+\returns
+\tcode{*(data() + idx)}.
+
+\pnum
+\throws
+Nothing.
 \end{itemdescr}
 
 \indexlibrarymember{span}{at}%
@@ -18867,8 +18871,12 @@
 \tcode{empty()} is \tcode{false}.
 
 \pnum
-\effects
-Equivalent to: \tcode{return *data();}
+\returns
+\tcode{*data()}.
+
+\pnum
+\throws
+Nothing.
 \end{itemdescr}
 
 \indexlibrarymember{span}{back}%
@@ -18882,8 +18890,12 @@
 \tcode{empty()} is \tcode{false}.
 
 \pnum
-\effects
-Equivalent to: \tcode{return *(data() + (size() - 1));}
+\returns
+\tcode{*(data() + (size() - 1))}.
+
+\pnum
+\throws
+Nothing.
 \end{itemdescr}
 
 \indexlibrarymember{span}{data}%
@@ -18893,8 +18905,8 @@
 
 \begin{itemdescr}
 \pnum
-\effects
-Equivalent to: \tcode{return \exposid{data_};}
+\returns
+\exposid{data_}.
 \end{itemdescr}
 
 \rSec4[span.iterators]{Iterator support}

source/future.tex

@@ -232,6 +232,7 @@
 \indexlibraryglobal{__alignas_is_defined}%
 \begin{codeblock}
 #define @\xname{alignas_is_defined}@ 1
+#define @\xname{alignof_is_defined}@ 1
 \end{codeblock}
 
 \pnum
@@ -2410,6 +2411,8 @@
 \begin{codeblock}
 codecvt<char16_t, char, mbstate_t>
 codecvt<char32_t, char, mbstate_t>
+codecvt<char16_t, char8_t, mbstate_t>
+codecvt<char32_t, char8_t, mbstate_t>
 \end{codeblock}
 
 \pnum
@@ -2420,18 +2423,22 @@
 \begin{codeblock}
 codecvt_byname<char16_t, char, mbstate_t>
 codecvt_byname<char32_t, char, mbstate_t>
+codecvt_byname<char16_t, char8_t, mbstate_t>
+codecvt_byname<char32_t, char8_t, mbstate_t>
 \end{codeblock}
 
 \pnum
 The following class template specializations are required
 in addition to those specified in~\ref{locale.codecvt}.
 \indextext{UTF-8}%
 \indextext{UTF-16}%
-The specialization \tcode{codecvt<char16_t, char, mbstate_t>}
-converts between the UTF-16 and UTF-8 encoding forms, and
+The specializations \tcode{codecvt<char16_t, char, mbstate_t>} and
+\tcode{codecvt<char16_t, char8_t, mbstate_t>}
+convert between the UTF-16 and UTF-8 encoding forms, and
 \indextext{UTF-32}%
-the specialization \tcode{codecvt<char32_t, char, mbstate_t>}
-converts between the UTF-32 and UTF-8 encoding forms.
+the specializations \tcode{codecvt<char32_t, char, mbstate_t>} and
+\tcode{codecvt<char32_t, char8_t, mbstate_t>}
+convert between the UTF-32 and UTF-8 encoding forms.
 
 \rSec1[depr.fs.path.factory]{Deprecated filesystem path factory functions}
 

source/iostreams.tex

@@ -3513,6 +3513,11 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\expects
+\range{gbeg}{gnext}, \range{gbeg}{gend}, and \range{gnext}{gend}
+are all valid ranges.
+
 \pnum
 \ensures
 \tcode{gbeg == eback()},
@@ -3573,6 +3578,10 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+\expects
+\range{pbeg}{pend} is a valid range.
+
 \pnum
 \ensures
 \tcode{pbeg == pbase()},

source/locales.tex

@@ -320,8 +320,6 @@
 collate     &   \tcode{collate<char>}, \tcode{collate<wchar_t>}                 \\ \rowsep
 ctype       &   \tcode{ctype<char>}, \tcode{ctype<wchar_t>}                     \\
             &   \tcode{codecvt<char, char, mbstate_t>}                            \\
-            &   \tcode{codecvt<char16_t, char8_t, mbstate_t>}        \\
-            &   \tcode{codecvt<char32_t, char8_t, mbstate_t>}        \\
             &   \tcode{codecvt<wchar_t, char, mbstate_t>}                         \\ \rowsep
 monetary    &   \tcode{moneypunct<char>}, \tcode{moneypunct<wchar_t>}           \\
             &   \tcode{moneypunct<char, true>}, \tcode{moneypunct<wchar_t, true>} \\
@@ -356,8 +354,6 @@
 collate     &   \tcode{collate_byname<char>}, \tcode{collate_byname<wchar_t>}       \\ \rowsep
 ctype       &   \tcode{ctype_byname<char>}, \tcode{ctype_byname<wchar_t>}           \\
             &   \tcode{codecvt_byname<char, char, mbstate_t>}                       \\
-            &   \tcode{codecvt_byname<char16_t, char8_t, mbstate_t>}                   \\
-            &   \tcode{codecvt_byname<char32_t, char8_t, mbstate_t>}                   \\
             &   \tcode{codecvt_byname<wchar_t, char, mbstate_t>}                    \\ \rowsep
 monetary    &   \tcode{moneypunct_byname<char, International>}                      \\
             &   \tcode{moneypunct_byname<wchar_t, International>}                   \\
@@ -978,18 +974,18 @@
     using mask = @\seebelow@;
 
     // numeric values are for exposition only.
-    static const mask space  = 1 << 0;
-    static const mask print  = 1 << 1;
-    static const mask cntrl  = 1 << 2;
-    static const mask upper  = 1 << 3;
-    static const mask lower  = 1 << 4;
-    static const mask alpha  = 1 << 5;
-    static const mask digit  = 1 << 6;
-    static const mask punct  = 1 << 7;
-    static const mask xdigit = 1 << 8;
-    static const mask blank  = 1 << 9;
-    static const mask alnum  = alpha | digit;
-    static const mask graph  = alnum | punct;
+    static constexpr mask space  = 1 << 0;
+    static constexpr mask print  = 1 << 1;
+    static constexpr mask cntrl  = 1 << 2;
+    static constexpr mask upper  = 1 << 3;
+    static constexpr mask lower  = 1 << 4;
+    static constexpr mask alpha  = 1 << 5;
+    static constexpr mask digit  = 1 << 6;
+    static constexpr mask punct  = 1 << 7;
+    static constexpr mask xdigit = 1 << 8;
+    static constexpr mask blank  = 1 << 9;
+    static constexpr mask alnum  = alpha | digit;
+    static constexpr mask graph  = alnum | punct;
   };
 }
 \end{codeblock}
@@ -1684,13 +1680,6 @@
 convert the implementation-defined native character set.
 \tcode{codecvt<char, char, mbstate_t>} implements a degenerate conversion;
 it does not convert at all.
-\indextext{UTF-8}%
-\indextext{UTF-16}%
-\indextext{UTF-32}%
-The specialization \tcode{codecvt<char16_t, char8_t, mbstate_t>}
-converts between the UTF-16 and UTF-8 encoding forms, and
-the specialization \tcode{codecvt<char32_t, char8_t, mbstate_t>}
-converts between the UTF-32 and UTF-8 encoding forms.
 \tcode{codecvt<wchar_t, char, mbstate_t>}
 converts between the native character sets for ordinary and wide characters.
 Specializations on \tcode{mbstate_t}
@@ -4751,6 +4740,7 @@
 The set of aliases of a known registered character encoding is an
 \impldef{set of aliases of a known registered character encoding}
 superset of the aliases specified in the IANA Character Sets registry.
+The set of aliases for US-ASCII includes ``ASCII''.
 No two aliases or primary names of distinct registered character encodings
 are equivalent when compared by \tcode{text_encoding::\exposid{comp-name}}.
 
@@ -5073,6 +5063,11 @@
 \tcode{ranges::range_value_t<text_encoding::aliases_view>} and
 \tcode{ranges::range_reference_t<text_encoding::aliases_view>}
 denote \tcode{const char*}.
+
+\pnum
+%FIXME: Is this supposed to be a remark or a requirement? Same above?
+\tcode{ranges::iterator_t<text_encoding::aliases_view>}
+is a constexpr iterator\iref{iterator.requirements.general}.
 \end{itemdescr}
 
 \rSec3[text.encoding.id]{Enumeration \tcode{text_encoding::id}}

source/ranges.tex

@@ -2248,25 +2248,33 @@
 \end{codeblock}
 
 \pnum
-Let \exposid{container-insertable} be defined as follows:
+Let \exposid{container-appendable} be defined as follows:
 \begin{codeblock}
 template<class Container, class Ref>
-constexpr bool @\exposid{container-insertable}@ =          // \expos
+constexpr bool @\exposid{container-appendable}@ =          // \expos
   requires(Container& c, Ref&& ref) {
-    requires (requires { c.push_back(std::forward<Ref>(ref)); } ||
+    requires (requires { c.emplace_back(std::forward<Ref>(ref)); } ||
+              requires { c.push_back(std::forward<Ref>(ref)); } ||
+              requires { c.emplace(c.end(), std::forward<Ref>(ref)); } ||
               requires { c.insert(c.end(), std::forward<Ref>(ref)); });
   };
 \end{codeblock}
 
 \pnum
-Let \exposid{container-inserter} be defined as follows:
+Let \exposid{container-appendable} be defined as follows:
 \begin{codeblock}
 template<class Ref, class Container>
-constexpr auto @\exposid{container-inserter}@(Container& c) {                // \expos
-  if constexpr (requires { c.push_back(declval<Ref>()); })
-    return back_inserter(c);
-  else
-    return inserter(c, c.end());
+constexpr auto @\exposid{container-appendable}@(Container& c) {                // \expos
+  return [&c]<class Ref>(Ref&& ref) {
+    if constexpr (requires { c.emplace_back(declval<Ref>()); })
+      c.emplace_back(std::forward<Ref>(ref));
+    else if constexpr (requires { c.push_back(declval<Ref>()); })
+      c.push_back(std::forward<Ref>(ref));
+    else if constexpr (requires { c.emplace(c.end(), declval<Ref>()); })
+      c.emplace(c.end(), std::forward<Ref>(ref));
+    else
+      c.insert(c.end(), std::forward<Ref>(ref));
+  };
 }
 \end{codeblock}
 
@@ -2328,13 +2336,13 @@
 \item
 \tcode{\libconcept{constructible_from}<C, Args...>} is \tcode{true}, and
 \item
-\tcode{\exposid{container-insertable}<C, range_reference_t<R>>} is \tcode{true}:
+\tcode{\exposid{container-appendable}<C, range_reference_t<R>>} is \tcode{true}:
 \end{itemize}
 \begin{codeblock}
 C c(std::forward<Args>(args)...);
 if constexpr (@\libconcept{sized_range}@<R> && @\exposid{reservable-container}@<C>)
   c.reserve(static_cast<range_size_t<C>>(ranges::size(r)));
-ranges::copy(r, @\exposid{container-inserter}@<range_reference_t<R>>(c));
+ranges::for_each(r, @\exposid{container-append}@(c));
 \end{codeblock}
 \item
 Otherwise, the program is ill-formed.
@@ -2344,7 +2352,7 @@
 Otherwise,
 if \tcode{\libconcept{input_range}<range_reference_t<R>>} is \tcode{true}:
 \begin{codeblock}
-to<C>(r | views::transform([](auto&& elem) {
+to<C>(ref_view(r) | views::transform([](auto&& elem) {
   return to<range_value_t<C>>(std::forward<decltype(elem)>(elem));
 }), std::forward<Args>(args)...);
 \end{codeblock}
@@ -2533,6 +2541,7 @@
     constexpr const T* begin() const noexcept;
     constexpr T* end() noexcept;
     constexpr const T* end() const noexcept;
+    static constexpr bool empty() noexcept;
     static constexpr size_t size() noexcept;
     constexpr T* data() noexcept;
     constexpr const T* data() const noexcept;
@@ -2603,6 +2612,17 @@
 Equivalent to: \tcode{return data() + 1;}
 \end{itemdescr}
 
+\indexlibrarymember{empty}{single_view}%
+\begin{itemdecl}
+static constexpr bool empty() noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return false;}
+\end{itemdescr}
+
 \indexlibrarymember{size}{single_view}%
 \begin{itemdecl}
 static constexpr size_t size() noexcept;
@@ -3406,7 +3426,7 @@
 Given subexpressions \tcode{E} and \tcode{F},
 the expressions \tcode{views::repeat(E)} and \tcode{views::repeat(E, F)}
 are expression-equivalent to
-\tcode{repeat_view(E)} and \tcode{repeat_view(E, F)}, respectively.
+\tcode{repeat_view<decay_t<decltype((E))>>(E)} and \tcode{repeat_view(E, F)}, respectively.
 
 \pnum
 \begin{example}
@@ -3456,8 +3476,8 @@
     constexpr auto size() const requires (!@\libconcept{same_as}@<Bound, unreachable_sentinel_t>);
   };
 
-  template<class T, class Bound>
-    repeat_view(T, Bound) -> repeat_view<T, Bound>;
+  template<class T, class Bound = unreachable_sentinel_t>
+    repeat_view(T, Bound = Bound()) -> repeat_view<T, Bound>;
 }
 \end{codeblock}
 
@@ -7909,10 +7929,9 @@
   private:
     @\exposid{outer-iterator}@ @\exposid{i_}@ = @\exposid{outer-iterator}@();               // \expos
 
-  public:
-    value_type() = default;
-    constexpr explicit value_type(@\exposid{outer-iterator}@ i);
+    constexpr explicit value_type(@\exposid{outer-iterator}@ i);    // \expos
 
+  public:
     constexpr @\exposid{inner-iterator}@<Const> begin() const;
     constexpr default_sentinel_t end() const noexcept;
   };
@@ -8542,7 +8561,7 @@
     constexpr V base() const & requires @\libconcept{copy_constructible}@<V> { return @\exposid{base_}@; }
     constexpr V base() && { return std::move(@\exposid{base_}@); }
 
-    constexpr auto begin() {
+    constexpr auto begin() requires (!@\exposconcept{simple-view}@<V>) {
       if constexpr (@\libconcept{random_access_range}@<V> && @\libconcept{sized_range}@<V>)
         return ranges::begin(@\exposid{base_}@);
       else
@@ -8556,7 +8575,7 @@
         return common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::begin(@\exposid{base_}@));
     }
 
-    constexpr auto end() {
+    constexpr auto end() requires (!@\exposconcept{simple-view}@<V>) {
       if constexpr (@\libconcept{random_access_range}@<V> && @\libconcept{sized_range}@<V>)
         return ranges::begin(@\exposid{base_}@) + ranges::distance(@\exposid{base_}@);
       else
@@ -9539,13 +9558,13 @@
     { return @\exposid{iterator}@<true>(ranges::begin(@\exposid{base_}@), 0); }
 
     constexpr auto end() requires (!@\exposconcept{simple-view}@<V>) {
-      if constexpr (@\libconcept{common_range}@<V> && @\libconcept{sized_range}@<V>)
+      if constexpr (@\libconcept{forward_range}@<V> && @\libconcept{common_range}@<V> && @\libconcept{sized_range}@<V>)
         return @\exposid{iterator}@<false>(ranges::end(@\exposid{base_}@), ranges::distance(@\exposid{base_}@));
       else
         return @\exposid{sentinel}@<false>(ranges::end(@\exposid{base_}@));
     }
     constexpr auto end() const requires @\exposconcept{range-with-movable-references}@<const V> {
-      if constexpr (@\libconcept{common_range}@<const V> && @\libconcept{sized_range}@<const V>)
+      if constexpr (@\libconcept{forward_range}@<const V> && @\libconcept{common_range}@<const V> && @\libconcept{sized_range}@<const V>)
         return @\exposid{iterator}@<true>(ranges::end(@\exposid{base_}@), ranges::distance(@\exposid{base_}@));
       else
         return @\exposid{sentinel}@<true>(ranges::end(@\exposid{base_}@));