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Aug 16, 2022
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P2165R4 Compatibility between tuple and tuple-like objects #5694

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8 changes: 4 additions & 4 deletions source/containers.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -9308,14 +9308,14 @@
typename iterator_traits<InputIterator>::value_type; // \expos
template<class InputIterator>
using @\placeholder{iter-key-type}@ = remove_const_t<
typename iterator_traits<InputIterator>::value_type::first_type>; // \expos
tuple_element_t<0, @\exposid{iter-value-type}@<InputIterator>>>; // \expos
template<class InputIterator>
using @\placeholder{iter-mapped-type}@ =
typename iterator_traits<InputIterator>::value_type::second_type; // \expos
tuple_element_t<1, @\exposid{iter-value-type}@<InputIterator>>; // \expos
template<class InputIterator>
using @\placeholder{iter-to-alloc-type}@ = pair<
add_const_t<typename iterator_traits<InputIterator>::value_type::first_type>,
typename iterator_traits<InputIterator>::value_type::second_type>; // \expos
add_const_t<tuple_element_t<0, @\exposid{iter-value-type}@<InputIterator>>>,
tuple_element_t<1, @\exposid{iter-value-type}@<InputIterator>>>; // \expos
template<ranges::@\libconcept{input_range}@ Range>
using @\exposid{range-key-type}@ =
remove_const_t<typename ranges::range_value_t<Range>::first_type>; // \expos
Expand Down
52 changes: 11 additions & 41 deletions source/ranges.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -1677,20 +1677,9 @@
@\libconcept{convertible_to}@<From, To> &&
!@\exposconcept{uses-nonqualification-pointer-conversion}@<decay_t<From>, decay_t<To>>;

template<class T>
concept @\defexposconceptnc{pair-like}@ = // \expos
!is_reference_v<T> && requires(T t) {
typename tuple_size<T>::type; // ensures \tcode{tuple_size<T>} is complete
requires @\libconcept{derived_from}@<tuple_size<T>, integral_constant<size_t, 2>>;
typename tuple_element_t<0, remove_const_t<T>>;
typename tuple_element_t<1, remove_const_t<T>>;
{ std::get<0>(t) } -> @\libconcept{convertible_to}@<const tuple_element_t<0, T>&>;
{ std::get<1>(t) } -> @\libconcept{convertible_to}@<const tuple_element_t<1, T>&>;
};

template<class T, class U, class V>
concept @\defexposconceptnc{pair-like-convertible-from}@ = // \expos
!@\libconcept{range}@<T> && @\exposconcept{pair-like}@<T> &&
!@\libconcept{range}@<T> && !is_reference_v<T> && @\exposconcept{pair-like}@<T> &&
@\libconcept{constructible_from}@<T, U, V> &&
@\exposconcept{convertible-to-non-slicing}@<U, tuple_element_t<0, T>> &&
@\libconcept{convertible_to}@<V, tuple_element_t<1, T>>;
Expand Down Expand Up @@ -7959,12 +7948,7 @@
namespace std::ranges {
template<class T, size_t N>
concept @\defexposconcept{has-tuple-element}@ = // \expos
requires(T t) {
typename tuple_size<T>::type;
requires N < tuple_size_v<T>;
typename tuple_element_t<N, T>;
{ std::get<N>(t) } -> @\libconcept{convertible_to}@<const tuple_element_t<N, T>&>;
};
@\exposconcept{tuple-like}@<T> && N < tuple_size_v<T>;

template<class T, size_t N>
concept @\defexposconcept{returnable-element}@ = // \expos
Expand Down Expand Up @@ -8594,13 +8578,10 @@
(!(@\libconcept{bidirectional_range}@<Rs> && ...) && (@\libconcept{common_range}@<Rs> && ...)) ||
((@\libconcept{random_access_range}@<Rs> && ...) && (@\libconcept{sized_range}@<Rs> && ...));

template<class... Ts>
using @\exposid{tuple-or-pair}@ = @\seebelow@; // \expos

template<class F, class Tuple>
constexpr auto @\exposid{tuple-transform}@(F&& f, Tuple&& tuple) { // \expos
return apply([&]<class... Ts>(Ts&&... elements) {
return @\exposid{tuple-or-pair}@<invoke_result_t<F&, Ts>...>(
return tuple<invoke_result_t<F&, Ts>...>(
invoke(f, std::forward<Ts>(elements))...
);
}, std::forward<Tuple>(tuple));
Expand Down Expand Up @@ -8664,17 +8645,6 @@
}
\end{codeblock}

\pnum
Given some pack of types \tcode{Ts},
the alias template \exposid{tuple-or-pair} is defined as follows:
\begin{itemize}
\item
If \tcode{sizeof...(Ts)} is 2,
\tcode{\exposid{tuple-or-pair}<Ts...>} denotes \tcode{pair<Ts...>}.
\item
Otherwise, \tcode{\exposid{tuple-or-pair}<Ts...>} denotes \tcode{tuple<Ts...>}.
\end{itemize}

\pnum
Two \tcode{zip_view} objects have the same underlying sequence if and only if
the corresponding elements of \exposid{views_} are equal\iref{concepts.equality}
Expand Down Expand Up @@ -8731,13 +8701,13 @@
requires (@\libconcept{view}@<Views> && ...) && (sizeof...(Views) > 0)
template<bool Const>
class zip_view<Views...>::@\exposid{iterator}@ {
@\exposid{tuple-or-pair}@<iterator_t<@\exposidnc{maybe-const}@<Const, Views>>...> @\exposid{current_}@;@\itcorr[-1]@ // \expos
constexpr explicit @\exposidnc{iterator}@(@\exposid{tuple-or-pair}@<iterator_t<@\exposidnc{maybe-const}@<Const, Views>>...>);
tuple<iterator_t<@\exposidnc{maybe-const}@<Const, Views>>...> @\exposid{current_}@;@\itcorr[-1]@ // \expos
constexpr explicit @\exposidnc{iterator}@(tuple<iterator_t<@\exposidnc{maybe-const}@<Const, Views>>...>);
// \expos
public:
using iterator_category = input_iterator_tag; // not always present
using iterator_concept = @\seebelow@;
using value_type = @\exposid{tuple-or-pair}@<range_value_t<@\exposid{maybe-const}@<Const, Views>>...>;
using value_type = tuple<range_value_t<@\exposid{maybe-const}@<Const, Views>>...>;
using difference_type = common_type_t<range_difference_t<@\exposid{maybe-const}@<Const, Views>>...>;

@\exposid{iterator}@() = default;
Expand Down Expand Up @@ -8813,7 +8783,7 @@
the iterator acquires a singular value.

\begin{itemdecl}
constexpr explicit @\exposid{iterator}@(@\exposid{tuple-or-pair}@<iterator_t<@\exposid{maybe-const}@<Const, Views>>...> current);
constexpr explicit @\exposid{iterator}@(tuple<iterator_t<@\exposid{maybe-const}@<Const, Views>>...> current);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -9104,8 +9074,8 @@
requires (@\libconcept{view}@<Views> && ...) && (sizeof...(Views) > 0)
template<bool Const>
class zip_view<Views...>::@\exposid{sentinel}@ {
@\exposid{tuple-or-pair}@<sentinel_t<@\exposidnc{maybe-const}@<Const, Views>>...> @\exposid{end_}@;@\itcorr[-1]@ // \expos
constexpr explicit @\exposidnc{sentinel}@(@\exposid{tuple-or-pair}@<sentinel_t<@\exposidnc{maybe-const}@<Const, Views>>...> end);
tuple<sentinel_t<@\exposidnc{maybe-const}@<Const, Views>>...> @\exposid{end_}@;@\itcorr[-1]@ // \expos
constexpr explicit @\exposidnc{sentinel}@(tuple<sentinel_t<@\exposidnc{maybe-const}@<Const, Views>>...> end);
// \expos
public:
@\exposid{sentinel}@() = default;
Expand Down Expand Up @@ -9134,7 +9104,7 @@
\end{codeblock}

\begin{itemdecl}
constexpr explicit @\exposid{sentinel}@(@\exposid{tuple-or-pair}@<sentinel_t<@\exposid{maybe-const}@<Const, Views>>...> end);
constexpr explicit @\exposid{sentinel}@(tuple<sentinel_t<@\exposid{maybe-const}@<Const, Views>>...> end);
\end{itemdecl}

\begin{itemdescr}
Expand Down Expand Up @@ -9879,7 +9849,7 @@
public:
using iterator_category = input_iterator_tag;
using iterator_concept = @\seebelow@;
using value_type = @\exposid{tuple-or-pair}@<@\exposid{REPEAT}@(range_value_t<@\exposid{Base}@>, N)...>;
using value_type = tuple<@\exposid{REPEAT}@(range_value_t<@\exposid{Base}@>, N)...>;
using difference_type = range_difference_t<@\exposid{Base}@>;

@\exposid{iterator}@() = default;
Expand Down
2 changes: 2 additions & 0 deletions source/support.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -718,6 +718,8 @@
#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}
#define @\defnlibxname{cpp_lib_tuple_like}@ 202207L
// also in \libheader{utility}, \libheader{tuple}, \libheader{map}, \libheader{unordered_map}
#define @\defnlibxname{cpp_lib_tuple_element_t}@ 201402L // also in \libheader{tuple}
#define @\defnlibxname{cpp_lib_tuples_by_type}@ 201304L // also in \libheader{utility}, \libheader{tuple}
#define @\defnlibxname{cpp_lib_type_identity}@ 201806L // also in \libheader{type_traits}
Expand Down
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