[range.chunk.fwd.iter]

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

## 25.7 Range adaptors [[range.adaptors]](range.adaptors#range.chunk.fwd.iter)

### 25.7.29 Chunk view [[range.chunk]](range.chunk#fwd.iter)

#### 25.7.29.7 Class template chunk_view​::​*iterator* for forward ranges [range.chunk.fwd.iter]

[ð](#lib:chunk_view::iterator)

namespace std::ranges {template<[view](range.view#concept:view "25.4.5 Views [range.view]") V>requires [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<V>template<bool Const>class chunk_view<V>::*iterator* {using *Parent* = *maybe-const*<Const, chunk_view>; // *exposition only*using *Base* = *maybe-const*<Const, V>; // *exposition only* iterator_t<*Base*> *current_* = iterator_t<*Base*>(); // *exposition only* sentinel_t<*Base*> *end_* = sentinel_t<*Base*>(); // *exposition only* range_difference_t<*Base*> *n_* = 0; // *exposition only* range_difference_t<*Base*> *missing_* = 0; // *exposition only*constexpr *iterator*(*Parent** parent, iterator_t<*Base*> current, // *exposition only* range_difference_t<*Base*> missing = 0); public:using iterator_category = input_iterator_tag; using iterator_concept = *see below*; using value_type = decltype(views::take(subrange(*current_*, *end_*), *n_*)); using difference_type = range_difference_t<*Base*>; *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<V>, iterator_t<*Base*>>&& [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<*Base*>>; constexpr iterator_t<*Base*> base() const; constexpr value_type operator*() const; constexpr *iterator*& operator++(); constexpr *iterator* operator++(int); constexpr *iterator*& operator--() requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator* operator--(int) requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator*& operator+=(difference_type x)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator*& operator-=(difference_type x)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr value_type operator[](difference_type n) constrequires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator==(const *iterator*& x, const *iterator*& y); friend constexpr bool operator==(const *iterator*& x, default_sentinel_t); friend constexpr bool operator<(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator>(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator<=(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr bool operator>=(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*> &&[three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<iterator_t<*Base*>>; friend constexpr *iterator* operator+(const *iterator*& i, difference_type n)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr *iterator* operator+(difference_type n, const *iterator*& i)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; friend constexpr *iterator* operator-(const *iterator*& i, difference_type n)requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; 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<*Base*>, iterator_t<*Base*>>; friend constexpr difference_type operator-(default_sentinel_t y, const *iterator*& x)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<*Base*>>; friend constexpr difference_type operator-(const *iterator*& x, default_sentinel_t y)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<*Base*>>; };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14521)

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

- [(1.1)](#1.1)

  If *Base* models [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]"),
then iterator_concept denotes random_access_iterator_tag[.](#1.1.sentence-1)

- [(1.2)](#1.2)

  Otherwise, if *Base* models [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]"),
then iterator_concept denotes bidirectional_iterator_tag[.](#1.2.sentence-1)

- [(1.3)](#1.3)

  Otherwise, iterator_concept denotes forward_iterator_tag[.](#1.3.sentence-1)

[ð](#lib:chunk_view::iterator,constructor)

`constexpr iterator(Parent* parent, iterator_t<Base> current,
                   range_difference_t<Base> missing = 0);
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14541)

*Effects*: Initializes *current_* with current,*end_* with ranges​::​end(parent->*base_*),*n_* with parent->*n_*, and*missing_* with missing[.](#2.sentence-1)

[ð](#lib:chunk_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<V>, iterator_t<Base>>
                 && [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<sentinel_t<V>, sentinel_t<Base>>;
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14557)

*Effects*: Initializes *current_* with std​::​move(i.*current_*),*end_* with std​::​move(i.*end_*),*n_* with i.*n_*, and*missing_* with i.*missing_*[.](#3.sentence-1)

[ð](#lib:base,chunk_view::iterator)

`constexpr iterator_t<Base> base() const;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14571)

*Returns*: *current_*[.](#4.sentence-1)

[ð](#lib:operator*,chunk_view::iterator)

`constexpr value_type operator*() const;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14582)

*Preconditions*: *current_* != *end_* is true[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14586)

*Returns*: views​::​take(subrange(*current_*, *end_*), *n_*)[.](#6.sentence-1)

[ð](#lib:operator++,chunk_view::iterator)

`constexpr iterator& operator++();
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14597)

*Preconditions*: *current_* != *end_* is true[.](#7.sentence-1)

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14601)

*Effects*: Equivalent to:*missing_* = ranges::advance(*current_*, *n_*, *end_*);return *this;

[ð](#lib:operator++,chunk_view::iterator_)

`constexpr iterator operator++(int);
`

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14616)

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

[ð](#lib:operator--,chunk_view::iterator)

`constexpr iterator& operator--() requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14632)

*Effects*: Equivalent to:ranges::advance(*current_*, *missing_* - *n_*);*missing_* = 0;return *this;

[ð](#lib:operator--,chunk_view::iterator_)

`constexpr iterator operator--(int) requires [bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14648)

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

[ð](#lib:operator+=,chunk_view::iterator)

`constexpr iterator& operator+=(difference_type x)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14665)

*Preconditions*: If x is positive,ranges​::​distance(*current_*, *end_*) > *n_* * (x - 1) is true[.](#12.sentence-1)

[*Note [1](#note-1)*:

If x is negative, the *Effects* paragraph implies a precondition[.](#12.sentence-2)

â *end note*]

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14674)

*Effects*: Equivalent to:if (x > 0) { ranges::advance(*current_*, *n_* * (x - 1)); *missing_* = ranges::advance(*current_*, *n_*, *end_*);} else if (x < 0) { ranges::advance(*current_*, *n_* * x + *missing_*); *missing_* = 0;}return *this;

[ð](#lib:operator-=,chunk_view::iterator)

`constexpr iterator& operator-=(difference_type x)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14696)

*Effects*: Equivalent to: return *this += -x;

[ð](#lib:operator%5b%5d,chunk_view::iterator)

`constexpr value_type operator[](difference_type n) const
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[15](#15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14708)

*Returns*: *(*this + n)[.](#15.sentence-1)

[ð](#lib:operator-=,chunk_view::iterator_)

`friend constexpr bool operator==(const iterator& x, const iterator& y);
`

[16](#16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14719)

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

[ð](#lib:operator==,chunk_view::iterator)

`friend constexpr bool operator==(const iterator& x, default_sentinel_t);
`

[17](#17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14730)

*Returns*: x.*current_* == x.*end_*[.](#17.sentence-1)

[ð](#lib:operator%3c,chunk_view::iterator)

`friend constexpr bool operator<(const iterator& x, const iterator& y)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[18](#18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14742)

*Returns*: x.*current_* < y.*current_*[.](#18.sentence-1)

[ð](#lib:operator%3e,chunk_view::iterator)

`friend constexpr bool operator>(const iterator& x, const iterator& y)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[19](#19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14754)

*Effects*: Equivalent to: return y < x;

[ð](#lib:operator%3c=,chunk_view::iterator)

`friend constexpr bool operator<=(const iterator& x, const iterator& y)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[20](#20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14766)

*Effects*: Equivalent to: return !(y < x);

[ð](#lib:operator%3e=,chunk_view::iterator)

`friend constexpr bool operator>=(const iterator& x, const iterator& y)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[21](#21)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14778)

*Effects*: Equivalent to: return !(x < y);

[ð](#lib:operator%3c=%3e,chunk_view::iterator)

`friend constexpr auto operator<=>(const iterator& x, const iterator& y)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base> &&
           [three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<iterator_t<Base>>;
`

[22](#22)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14791)

*Returns*: x.*current_* <=> y.*current_*[.](#22.sentence-1)

[ð](#lib:operator+,chunk_view::iterator)

`friend constexpr iterator operator+(const iterator& i, difference_type n)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
friend constexpr iterator operator+(difference_type n, const iterator& i)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[23](#23)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14805)

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

[ð](#lib:operator-,chunk_view::iterator)

`friend constexpr iterator operator-(const iterator& i, difference_type n)
  requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<Base>;
`

[24](#24)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14822)

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

[ð](#lib:operator-,chunk_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<Base>, iterator_t<Base>>;
`

[25](#25)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14839)

*Returns*: (x.*current_* - y.*current_* + x.*missing_* - y.*missing_*) / x.*n_*[.](#25.sentence-1)

[ð](#lib:operator-,chunk_view::iterator__)

`friend constexpr difference_type operator-(default_sentinel_t y, const iterator& x)
  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<Base>>;
`

[26](#26)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14851)

*Returns*: *div-ceil*(x.*end_* - x.*current_*, x.*n_*)[.](#26.sentence-1)

[ð](#lib:operator-,chunk_view::iterator___)

`friend constexpr difference_type operator-(const iterator& x, default_sentinel_t y)
  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<Base>>;
`

[27](#27)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L14863)

*Effects*: Equivalent to: return -(y - x);
