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cppdraft/range/elements/overview.md

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+[range.elements.overview]
+
+# 25 Ranges library [[ranges]](./#ranges)
+
+## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.elements.overview)
+
+### 25.7.23 Elements view [[range.elements]](range.elements#overview)
+
+#### 25.7.23.1 Overview [range.elements.overview]
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10131)
+
+elements_view takes
+a view of tuple-like values and a size_t, and
+produces a view with a value-type of the Nth element
+of the adapted view's value-type[.](#1.sentence-1)
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10137)
+
+The name views​::​elements<N> denotes
+a range adaptor object ([[range.adaptor.object]](range.adaptor.object "25.7.2 Range adaptor objects"))[.](#2.sentence-1)
+
+Given a subexpression E and constant expression N,
+the expression views​::​elements<N>(E) is expression-equivalent toelements_view<views​::​all_t<decltype((E))>, N>{E}[.](#2.sentence-2)
+
+[*Example [1](#example-1)*: auto historical_figures = map{ pair{"Lovelace"sv, 1815}, {"Turing"sv, 1912}, {"Babbage"sv, 1791}, {"Hamilton"sv, 1936}};
+
+auto names = historical_figures | views::elements<0>;for (auto&& name : names) { cout << name << ' '; // prints Babbage Hamilton Lovelace Turing }auto birth_years = historical_figures | views::elements<1>;for (auto&& born : birth_years) { cout << born << ' '; // prints 1791 1936 1815 1912 } — *end example*]
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10166)
+
+keys_view is an alias for elements_view<R, 0>, and
+is useful for extracting keys from associative containers[.](#3.sentence-1)
+
+[*Example [2](#example-2)*: auto names = historical_figures | views::keys;for (auto&& name : names) { cout << name << ' '; // prints Babbage Hamilton Lovelace Turing } — *end example*]
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10179)
+
+values_view is an alias for elements_view<R, 1>, and
+is useful for extracting values from associative containers[.](#4.sentence-1)
+
+[*Example [3](#example-3)*: auto is_even = [](const auto x) { return x % 2 == 0; };
+cout << ranges::count_if(historical_figures | views::values, is_even); // prints 2 — *end example*]

cppdraft/range/elements/sentinel.md

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+[range.elements.sentinel]
+
+# 25 Ranges library [[ranges]](./#ranges)
+
+## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.elements.sentinel)
+
+### 25.7.23 Elements view [[range.elements]](range.elements#sentinel)
+
+#### 25.7.23.4 Class template elements_view​::​*sentinel* [range.elements.sentinel]
+
+[🔗](#lib:elements_view::sentinel)
+
+namespace std::ranges {template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") V, size_t N>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && [*has-tuple-element*](range.elements.view#concept:has-tuple-element "25.7.23.2 Class template elements_­view [range.elements.view]")<range_value_t<V>, N> &&[*has-tuple-element*](range.elements.view#concept:has-tuple-element "25.7.23.2 Class template elements_­view [range.elements.view]")<remove_reference_t<range_reference_t<V>>, N> &&[*returnable-element*](range.elements.view#concept:returnable-element "25.7.23.2 Class template elements_­view [range.elements.view]")<range_reference_t<V>, N>template<bool Const>class elements_view<V, N>::*sentinel* {private:using *Base* = *maybe-const*<Const, V>; // *exposition only* sentinel_t<*Base*> *end_* = sentinel_t<*Base*>(); // *exposition only*public:*sentinel*() = default; constexpr explicit *sentinel*(sentinel_t<*Base*> end); constexpr *sentinel*(*sentinel*<!Const> other)requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<*Base*>>; constexpr sentinel_t<*Base*> base() const; template<bool OtherConst>requires [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr bool operator==(const *iterator*<OtherConst>& x, const *sentinel*& y); template<bool OtherConst>requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr range_difference_t<*maybe-const*<OtherConst, V>>operator-(const *iterator*<OtherConst>& x, const *sentinel*& y); template<bool OtherConst>requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<*Base*>, iterator_t<*maybe-const*<OtherConst, V>>>friend constexpr range_difference_t<*maybe-const*<OtherConst, V>>operator-(const *sentinel*& x, const *iterator*<OtherConst>& y); };}
+
+[🔗](#lib:elements_view::sentinel,constructor)
+
+`constexpr explicit sentinel(sentinel_t<Base> end);
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10717)
+
+*Effects*: Initializes *end_* with end[.](#1.sentence-1)
+
+[🔗](#lib:elements_view::sentinel,constructor_)
+
+`constexpr sentinel(sentinel<!Const> other)
+  requires Const && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<Base>>;
+`
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10729)
+
+*Effects*: Initializes *end_* with std​::​move(other.*end_*)[.](#2.sentence-1)
+
+[🔗](#lib:base,elements_view::sentinel)
+
+`constexpr sentinel_t<Base> base() const;
+`
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10740)
+
+*Effects*: Equivalent to: return *end_*;
+
+[🔗](#lib:operator==,elements_view::sentinel)
+
+`template<bool OtherConst>
+  requires [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
+friend constexpr bool operator==(const iterator<OtherConst>& x, const sentinel& y);
+`
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10753)
+
+*Effects*: Equivalent to: return x.*current_* == y.*end_*;
+
+[🔗](#lib:operator-,elements_view::sentinel)
+
+`template<bool OtherConst>
+  requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
+friend constexpr range_difference_t<maybe-const<OtherConst, V>>
+  operator-(const iterator<OtherConst>& x, const sentinel& y);
+`
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10767)
+
+*Effects*: Equivalent to: return x.*current_* - y.*end_*;
+
+[🔗](#lib:operator-,elements_view::sentinel_)
+
+`template<bool OtherConst>
+  requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<sentinel_t<Base>, iterator_t<maybe-const<OtherConst, V>>>
+friend constexpr range_difference_t<maybe-const<OtherConst, V>>
+  operator-(const sentinel& x, const iterator<OtherConst>& y);
+`
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10781)
+
+*Effects*: Equivalent to: return x.*end_* - y.*current_*;

cppdraft/range/elements/view.md

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+[range.elements.view]
+
+# 25 Ranges library [[ranges]](./#ranges)
+
+## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.elements.view)
+
+### 25.7.23 Elements view [[range.elements]](range.elements#view)
+
+#### 25.7.23.2 Class template elements_view [range.elements.view]
+
+[🔗](#lib:elements_view)
+
+namespace std::ranges {template<class T, size_t N>concept [*has-tuple-element*](#concept:has-tuple-element "25.7.23.2 Class template elements_­view [range.elements.view]") = // *exposition only*[*tuple-like*](tuple.like#concept:tuple-like "22.4.3 Concept tuple-like [tuple.like]")<T> && N < tuple_size_v<T>; template<class T, size_t N>concept [*returnable-element*](#concept:returnable-element "25.7.23.2 Class template elements_­view [range.elements.view]") = // *exposition only* is_reference_v<T> || [move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_­constructible [concept.moveconstructible]")<tuple_element_t<N, T>>; template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") V, size_t N>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V> && [*has-tuple-element*](#concept:has-tuple-element "25.7.23.2 Class template elements_­view [range.elements.view]")<range_value_t<V>, N> &&[*has-tuple-element*](#concept:has-tuple-element "25.7.23.2 Class template elements_­view [range.elements.view]")<remove_reference_t<range_reference_t<V>>, N> &&[*returnable-element*](#concept:returnable-element "25.7.23.2 Class template elements_­view [range.elements.view]")<range_reference_t<V>, N>class elements_view : public view_interface<elements_view<V, N>> {public: elements_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<V> = default; constexpr explicit elements_view(V base); constexpr V base() const & requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<V> { return *base_*; }constexpr V base() && { return std::move(*base_*); }constexpr auto begin() requires (![*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V>){ return *iterator*<false>(ranges::begin(*base_*)); }constexpr auto begin() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V>{ return *iterator*<true>(ranges::begin(*base_*)); }constexpr auto end() requires (![*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V> && ![common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<V>){ return *sentinel*<false>{ranges::end(*base_*)}; }constexpr auto end() requires (![*simple-view*](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V> && [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<V>){ return *iterator*<false>{ranges::end(*base_*)}; }constexpr auto end() const requires [range](range.range#concept:range "25.4.2 Ranges [range.range]")<const V>{ return *sentinel*<true>{ranges::end(*base_*)}; }constexpr auto end() const requires [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")<const V>{ return *iterator*<true>{ranges::end(*base_*)}; }constexpr auto size() requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<V>{ return ranges::size(*base_*); }constexpr auto size() const requires [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<const V>{ return ranges::size(*base_*); }constexpr auto reserve_hint() requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<V>{ return ranges::reserve_hint(*base_*); }constexpr auto reserve_hint() const requires [approximately_sized_range](range.approximately.sized#concept:approximately_sized_range "25.4.3 Approximately sized ranges [range.approximately.sized]")<const V>{ return ranges::reserve_hint(*base_*); }private:// [[range.elements.iterator]](range.elements.iterator "25.7.23.3 Class template elements_­view​::​iterator"), class template elements_view​::​*iterator*template<bool> class *iterator*; // *exposition only*// [[range.elements.sentinel]](range.elements.sentinel "25.7.23.4 Class template elements_­view​::​sentinel"), class template elements_view​::​*sentinel*template<bool> class *sentinel*; // *exposition only* V *base_* = V(); // *exposition only*};}
+
+[🔗](#lib:elements_view,constructor)
+
+`constexpr explicit elements_view(V base);
+`
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L10267)
+
+*Effects*: Initializes *base_* with std​::​move(base)[.](#1.sentence-1)