cppdraft_translate/cppdraft/range/zip/iterator.md

[range.zip.iterator]

# 25 Ranges library [[ranges]](./#ranges)

## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.zip.iterator)

### 25.7.25 Zip view [[range.zip]](range.zip#iterator)

#### 25.7.25.3 Class template zip_view​::​*iterator* [range.zip.iterator]

[🔗](#lib:zip_view::iterator)

namespace std::ranges {template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]")... Views>requires ([view](range.view#concept:view "25.4.5 Views [range.view]")<Views> && ...) && (sizeof...(Views) > 0)template<bool Const>class zip_view<Views...>::*iterator* { tuple<iterator_t<*maybe-const*<Const, Views>>...> *current_*; // *exposition only*constexpr explicit *iterator*(tuple<iterator_t<*maybe-const*<Const, Views>>...>); // *exposition only*public:using iterator_category = input_iterator_tag; // not always presentusing iterator_concept = *see below*; using value_type = tuple<range_value_t<*maybe-const*<Const, Views>>...>; using difference_type = common_type_t<range_difference_t<*maybe-const*<Const, Views>>...>; *iterator*() = default; constexpr *iterator*(*iterator*<!Const> i)requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<Views>, iterator_t<const Views>> && ...); constexpr auto operator*() const; constexpr *iterator*& operator++(); constexpr void operator++(int); constexpr *iterator* operator++(int) requires [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; constexpr *iterator*& operator--() requires [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; constexpr *iterator* operator--(int) requires [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; constexpr *iterator*& operator+=(difference_type x)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; constexpr *iterator*& operator-=(difference_type x)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; constexpr auto operator[](difference_type n) constrequires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; friend constexpr bool operator==(const *iterator*& x, const *iterator*& y)requires ([equality_comparable](concept.equalitycomparable#concept:equality_comparable "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<iterator_t<*maybe-const*<Const, Views>>> && ...); friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; friend constexpr *iterator* operator+(const *iterator*& i, difference_type n)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; friend constexpr *iterator* operator+(difference_type n, const *iterator*& i)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; friend constexpr *iterator* operator-(const *iterator*& i, difference_type n)requires [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>; friend constexpr difference_type operator-(const *iterator*& x, const *iterator*& y)requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<iterator_t<*maybe-const*<Const, Views>>,
 iterator_t<*maybe-const*<Const, Views>>> && ...); friend constexpr auto iter_move(const *iterator*& i) noexcept(*see below*); friend constexpr void iter_swap(const *iterator*& l, const *iterator*& r) noexcept(*see below*)requires ([indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_­swappable [alg.req.ind.swap]")<iterator_t<*maybe-const*<Const, Views>>> && ...); };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11540)

*iterator*​::​iterator_concept is defined as follows:

- [(1.1)](#1.1)

  If [*all-random-access*](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...> is modeled,
then iterator_concept denotes random_access_iterator_tag[.](#1.1.sentence-1)

- [(1.2)](#1.2)

  Otherwise,
if [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...> is modeled,
then iterator_concept denotes bidirectional_iterator_tag[.](#1.2.sentence-1)

- [(1.3)](#1.3)

  Otherwise,
if [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...> is modeled,
then iterator_concept denotes forward_iterator_tag[.](#1.3.sentence-1)

- [(1.4)](#1.4)

  Otherwise, iterator_concept denotes input_iterator_tag[.](#1.4.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11558)

*iterator*​::​iterator_category is present
if and only if [*all-forward*](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...> is modeled[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11562)

If the invocation of any non-const member function of *iterator* exits via an exception,
the iterator acquires a singular value[.](#3.sentence-1)

[🔗](#lib:zip_view::iterator,constructor)

`constexpr explicit iterator(tuple<iterator_t<maybe-const<Const, Views>>...> current);
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11573)

*Effects*: Initializes *current_* with std​::​move(current)[.](#4.sentence-1)

[🔗](#lib:zip_view::iterator,constructor_)

`constexpr iterator(iterator<!Const> i)
  requires Const && ([convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<iterator_t<Views>, iterator_t<const Views>> && ...);
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11585)

*Effects*: Initializes *current_* with std​::​move(i.*current_*)[.](#5.sentence-1)

[🔗](#lib:operator*,izip_view::iterator)

`constexpr auto operator*() const;
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11596)

*Effects*: Equivalent to:return *tuple-transform*([](auto& i) -> decltype(auto) { return *i; }, *current_*);

[🔗](#lib:operator++,izip_view::iterator)

`constexpr iterator& operator++();
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11610)

*Effects*: Equivalent to:*tuple-for-each*([](auto& i) { ++i; }, *current_*);return *this;

[🔗](#lib:operator++,izip_view::iterator_)

`constexpr void operator++(int);
`

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11625)

*Effects*: Equivalent to ++*this[.](#8.sentence-1)

[🔗](#lib:operator++,izip_view::iterator__)

`constexpr iterator operator++(int) requires [all-forward](range.adaptor.helpers#concept:all-forward "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11636)

*Effects*: Equivalent to:auto tmp = *this;++*this;return tmp;

[🔗](#lib:operator--,izip_view::iterator)

`constexpr iterator& operator--() requires [all-bidirectional](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11652)

*Effects*: Equivalent to:*tuple-for-each*([](auto& i) { --i; }, *current_*);return *this;

[🔗](#lib:operator--,izip_view::iterator_)

`constexpr iterator operator--(int) requires [all-bidirectional](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11667)

*Effects*: Equivalent to:auto tmp = *this;--*this;return tmp;

[🔗](#lib:operator+=,izip_view::iterator)

`constexpr iterator& operator+=(difference_type x)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11684)

*Effects*: Equivalent to:*tuple-for-each*([&]<class I>(I& i) { i += iter_difference_t<I>(x); }, *current_*);return *this;

[🔗](#lib:operator-=,izip_view::iterator)

`constexpr iterator& operator-=(difference_type x)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11700)

*Effects*: Equivalent to:*tuple-for-each*([&]<class I>(I& i) { i -= iter_difference_t<I>(x); }, *current_*);return *this;

[🔗](#lib:operator%5b%5d,izip_view::iterator)

`constexpr auto operator[](difference_type n) const
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11716)

*Effects*: Equivalent to:return *tuple-transform*([&]<class I>(I& i) -> decltype(auto) {return i[iter_difference_t<I>(n)];}, *current_*);

[🔗](#lib:operator==,izip_view::iterator)

`friend constexpr bool operator==(const iterator& x, const iterator& y)
  requires ([equality_comparable](concept.equalitycomparable#concept:equality_comparable "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<iterator_t<maybe-const<Const, Views>>> && ...);
`

[15](#15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11733)

*Returns*: 

- [(15.1)](#15.1)

  x.*current_* == y.*current_* if [*all-bidirectional*](range.adaptor.helpers#concept:all-bidirectional "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...> is true[.](#15.1.sentence-1)

- [(15.2)](#15.2)

  Otherwise, true if there exists an integer 0≤i<sizeof...(Views) such that bool(std​::​​get<i>(x.*current_*) == std​::​get<i>(y.*current_*)) is true[.](#15.2.sentence-1)
  [*Note [1](#note-1)*:
  This allows zip_view to model [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]") when all constituent views model [common_range](range.refinements#concept:common_range "25.4.6 Other range refinements [range.refinements]")[.](#15.2.sentence-2)
 — *end note*]

- [(15.3)](#15.3)

  Otherwise, false[.](#15.3.sentence-1)

[🔗](#lib:operator%3c=%3e,izip_view::iterator)

`friend constexpr auto operator<=>(const iterator& x, const iterator& y)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[16](#16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11760)

*Returns*: x.*current_* <=> y.*current_*[.](#16.sentence-1)

[🔗](#lib:operator+,izip_view::iterator)

`friend constexpr iterator operator+(const iterator& i, difference_type n)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
friend constexpr iterator operator+(difference_type n, const iterator& i)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[17](#17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11774)

*Effects*: Equivalent to:auto r = i;
r += n;return r;

[🔗](#lib:operator-,izip_view::iterator)

`friend constexpr iterator operator-(const iterator& i, difference_type n)
  requires [all-random-access](range.adaptor.helpers#concept:all-random-access "25.7.5 Range adaptor helpers [range.adaptor.helpers]")<Const, Views...>;
`

[18](#18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11791)

*Effects*: Equivalent to:auto r = i;
r -= n;return r;

[🔗](#lib:operator-,izip_view::iterator_)

`friend constexpr difference_type operator-(const iterator& x, const iterator& y)
  requires ([sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<iterator_t<maybe-const<Const, Views>>,
                               iterator_t<maybe-const<Const, Views>>> && ...);
`

[19](#19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11809)

Let *DIST*(i) be difference_type(std​::​get<i>(x.*current_*) - std​::​get<i>(y.*current_*))[.](#19.sentence-1)

[20](#20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11812)

*Returns*: The value with the smallest absolute value among *DIST*(n) for all integers 0≤n<sizeof...(Views)[.](#20.sentence-1)

[🔗](#lib:iter_move,izip_view::iterator)

`friend constexpr auto iter_move(const iterator& i) noexcept(see below);
`

[21](#21)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11824)

*Effects*: Equivalent to:return *tuple-transform*(ranges::iter_move, i.*current_*);

[22](#22)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11831)

*Remarks*: The exception specification is equivalent to:(noexcept(ranges::iter_move(declval<const iterator_t<*maybe-const*<Const,
 Views>>&>())) && ...) &&(is_nothrow_move_constructible_v<range_rvalue_reference_t<*maybe-const*<Const,
 Views>>> && ...)

[🔗](#lib:iter_swap,izip_view::iterator)

`friend constexpr void iter_swap(const iterator& l, const iterator& r) noexcept(see below)
  requires ([indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_­swappable [alg.req.ind.swap]")<iterator_t<maybe-const<Const, Views>>> && ...);
`

[23](#23)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11849)

*Effects*: For every integer 0≤i<sizeof...(Views),
performs:ranges::iter_swap(std::get<i>(l.*current_*), std::get<i>(r.*current_*))

[24](#24)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L11857)

*Remarks*: The exception specification is equivalent to
the logical and of the following expressions:noexcept(ranges::iter_swap(std::get<i>(l.*current_*), std::get<i>(r.*current_*))) for every integer 0≤i<sizeof...(Views)[.](#24.sentence-1)