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Merge 2024-03 LWG Motion 16
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P2944R3 Comparisons for reference_wrapper
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@tkoeppe
tkoeppe committed Apr 16, 2024
2 parents 6569d4c + b4124f3 commit 5a7bb2f
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3 changes: 3 additions & 0 deletions source/support.tex
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#define @\defnlibxname{cpp_lib_constexpr_typeinfo}@ 202106L // freestanding, also in \libheader{typeinfo}
#define @\defnlibxname{cpp_lib_constexpr_utility}@ 201811L // freestanding, also in \libheader{utility}
#define @\defnlibxname{cpp_lib_constexpr_vector}@ 201907L // also in \libheader{vector}
#define @\defnlibxname{cpp_lib_constrained_equality}@ 202403L // freestanding,
// also in \libheader{utility}, \libheader{tuple}, \libheader{optional}, \libheader{variant}
#define @\defnlibxname{cpp_lib_containers_ranges}@ 202202L
// also in \libheader{vector}, \libheader{list}, \libheader{forward_list}, \libheader{map}, \libheader{set}, \libheader{unordered_map}, \libheader{unordered_set},
// \libheader{deque}, \libheader{queue}, \libheader{stack}, \libheader{string}
Expand Down Expand Up @@ -754,6 +756,7 @@
#define @\defnlibxname{cpp_lib_raw_memory_algorithms}@ 201606L // also in \libheader{memory}
#define @\defnlibxname{cpp_lib_rcu}@ 202306L // also in \libheader{rcu}
#define @\defnlibxname{cpp_lib_reference_from_temporary}@ 202202L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_reference_wrapper}@ 202403L // freestanding, also in \libheader{functional}
#define @\defnlibxname{cpp_lib_remove_cvref}@ 201711L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_result_of_sfinae}@ 201210L
// freestanding, also in \libheader{functional}, \libheader{type_traits}
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164 changes: 130 additions & 34 deletions source/utilities.tex
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Expand Up @@ -1282,9 +1282,11 @@

\begin{itemdescr}
\pnum
\expects
Each of \tcode{decltype(x.first == y.first)} and
\tcode{decltype(x.second == y.second)} models \exposconcept{boolean-testable}.
\constraints
\tcode{x.first == y.first} and \tcode{x.second == y.second} are
valid expressions and
each of \tcode{decltype(x.first == y.first)} and
\tcode{decltype(x.second == y.second)} models \exposconceptx{boolean-\newline testable}{boolean-testable}.

\pnum
\returns
Expand Down Expand Up @@ -2935,18 +2937,14 @@
For the first overload let \tcode{UTuple} be \tcode{tuple<UTypes...>}.

\pnum
\mandates
\constraints
For all \tcode{i},
where $0 \leq \tcode{i} < \tcode{sizeof...(TTypes)}$,
\tcode{get<i>(t) == get<i>(u)} is a valid expression.
\tcode{get<i>(t) == get<i>(u)} is a valid expression and
\tcode{decltype(get<i>(t) == get<i>(u))} models \exposconcept{boolean-testable}.
\tcode{sizeof...(TTypes)} equals
\tcode{tuple_size_v<UTuple>}.

\pnum
\expects
For all \tcode{i}, \tcode{decltype(get<i>(t) == get<i>(u))} models
\exposconcept{boolean-testable}.

\pnum
\returns
\tcode{true} if \tcode{get<i>(t) == get<i>(u)} for all
Expand Down Expand Up @@ -4399,7 +4397,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x == *y} is well-formed and
its result is convertible to \tcode{bool}.
\begin{note}
Expand All @@ -4424,7 +4422,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x != *y} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4448,7 +4446,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{*x < *y} is well-formed
and its result is convertible to \tcode{bool}.

Expand All @@ -4472,7 +4470,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x > *y} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4496,7 +4494,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x <= *y} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4520,7 +4518,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x >= *y} is well-formed and
its result is convertible to \tcode{bool}.

Expand Down Expand Up @@ -4589,7 +4587,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x == v} is well-formed and
its result is convertible to \tcode{bool}.
\begin{note}
Expand All @@ -4608,7 +4606,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v == *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4624,7 +4622,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x != v} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4640,7 +4638,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v != *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4656,7 +4654,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x < v} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4672,7 +4670,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v < *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4688,7 +4686,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x > v} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4704,7 +4702,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v > *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4720,7 +4718,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x <= v} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4736,7 +4734,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v <= *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4752,7 +4750,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{*x >= v} is well-formed and
its result is convertible to \tcode{bool}.

Expand All @@ -4768,7 +4766,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
The expression \tcode{v >= *x} is well-formed and
its result is convertible to \tcode{bool}.

Expand Down Expand Up @@ -5991,7 +5989,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) == \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand All @@ -6010,7 +6008,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) != \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand All @@ -6029,7 +6027,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) < \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand All @@ -6050,7 +6048,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) > \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand All @@ -6071,7 +6069,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) <= \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand All @@ -6092,7 +6090,7 @@

\begin{itemdescr}
\pnum
\mandates
\constraints
\tcode{\exposid{GET}<$i$>(v) >= \exposid{GET}<$i$>(w)} is a valid expression that is
convertible to \tcode{bool}, for all $i$.

Expand Down Expand Up @@ -10999,6 +10997,16 @@
template<class... ArgTypes>
constexpr invoke_result_t<T&, ArgTypes...> operator()(ArgTypes&&...) const
noexcept(is_nothrow_invocable_v<T&, ArgTypes...>);

// \ref{refwrap.comparisons}, comparisons
friend constexpr bool operator==(reference_wrapper, reference_wrapper);
friend constexpr bool operator==(reference_wrapper, const T&);
friend constexpr bool operator==(reference_wrapper, reference_wrapper<const T>);

friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper, reference_wrapper);
friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper, const T&);
friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper,
reference_wrapper<const T>);
};

template<class T>
Expand All @@ -11017,6 +11025,12 @@
\pnum
The template parameter \tcode{T} of \tcode{reference_wrapper}
may be an incomplete type.
\begin{note}
Using the comparison operators described in subclause \ref{refwrap.comparisons}
with \tcode{T} being an incomplete type
can lead to an ill-formed program
with no diagnostic required\iref{temp.point,temp.constr.atomic}.
\end{note}

\rSec3[refwrap.const]{Constructors}

Expand Down Expand Up @@ -11120,6 +11134,88 @@
\tcode{\placeholdernc{INVOKE}(get(), std::forward<ArgTypes>(args)...)}.\iref{func.require}
\end{itemdescr}

\rSec3[refwrap.comparisons]{Comparisons}

\begin{itemdecl}
friend constexpr bool operator==(reference_wrapper x, reference_wrapper y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\constraints
The expression \tcode{x.get() == y.get()} is well-formed and
its result is convertible to \tcode{bool}.

\pnum
\returns
\tcode{x.get() == y.get()}.
\end{itemdescr}

\begin{itemdecl}
friend constexpr bool operator==(reference_wrapper x, const T& y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\constraints
The expression \tcode{x.get() == y} is well-formed and
its result is convertible to \tcode{bool}.

\pnum
\returns
\tcode{x.get() == y}.
\end{itemdescr}

\begin{itemdecl}
friend constexpr bool operator==(reference_wrapper x, reference_wrapper<const T> y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\constraints
\tcode{is_const_v<T>} is \tcode{false} and
the expression \tcode{x.get() == y.get()} is well-formed and
its result is convertible to \tcode{bool}.

\pnum
\returns
\tcode{x.get() == y.get()}.
\end{itemdescr}

\begin{itemdecl}
friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper x, reference_wrapper y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\returns
\tcode{\exposid{synth-three-way}(x.get(), y.get())}.
\end{itemdescr}

\begin{itemdecl}
friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper x, const T& y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\returns
\tcode{\exposid{synth-three-way}(x.get(), y)}.
\end{itemdescr}

\begin{itemdecl}
friend constexpr @\exposidnc{synth-three-way-result}@<T> operator<=>(reference_wrapper x,
reference_wrapper<const T> y);
\end{itemdecl}

\begin{itemdescr}
\pnum
\constraints
\tcode{is_const_v<T>} is \tcode{false}.

\pnum
\returns
\tcode{\exposid{synth-three-way}(x.get(), y.get())}.
\end{itemdescr}

\rSec3[refwrap.helpers]{Helper functions}

Expand Down

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