[range.stride.iterator]

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

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

### 25.7.32 Stride view [[range.stride]](range.stride#iterator)

#### 25.7.32.3 Class template stride_view​::​*iterator* [range.stride.iterator]

[ð](#lib:stride_view::iterator)

namespace std::ranges {template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") V>requires [view](range.view#concept:view "25.4.5 Views [range.view]")<V>template<bool Const>class stride_view<V>::*iterator* {using *Parent* = *maybe-const*<Const, stride_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*> *stride_* = 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 difference_type = range_difference_t<*Base*>; using value_type = range_value_t<*Base*>; using iterator_concept = *see below*; using iterator_category = *see below*; // not always present*iterator*() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<iterator_t<*Base*>> = default; constexpr *iterator*(*iterator*<!Const> other)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() &&; constexpr const iterator_t<*Base*>& base() const & noexcept; constexpr decltype(auto) operator*() const { return **current_*; }constexpr *iterator*& operator++(); constexpr void operator++(int); constexpr *iterator* operator++(int) requires [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; 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 n) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr *iterator*& operator-=(difference_type n) requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>; constexpr decltype(auto) operator[](difference_type n) constrequires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<*Base*>{ return *(*this + n); }friend constexpr bool operator==(const *iterator*& x, default_sentinel_t); 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<*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 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*& x, 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*& x)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*& x, 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*>>; friend constexpr range_rvalue_reference_t<*Base*> iter_move(const *iterator*& i)noexcept(noexcept(ranges::iter_move(i.*current_*))); friend constexpr void iter_swap(const *iterator*& x, const *iterator*& y)noexcept(noexcept(ranges::iter_swap(x.*current_*, y.*current_*)))requires [indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_­swappable [alg.req.ind.swap]")<iterator_t<*Base*>>; };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16161)

*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, if *Base* models [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]"),
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#L16177)

The member [*typedef-name*](dcl.typedef#nt:typedef-name "9.2.4 The typedef specifier [dcl.typedef]") iterator_category is defined
if and only if *Base* models [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")[.](#2.sentence-1)

In that case,*iterator*​::​iterator_category is defined as follows:

- [(2.1)](#2.1)

  Let C denote
the type iterator_traits<iterator_t<*Base*>>​::​iterator_category[.](#2.1.sentence-1)

- [(2.2)](#2.2)

  If C models[derived_from](concept.derived#concept:derived_from "18.4.3 Concept derived_­from [concept.derived]")<random_access_iterator_tag>,
then iterator_category denotes random_access_iterator_tag[.](#2.2.sentence-1)

- [(2.3)](#2.3)

  Otherwise, iterator_category denotes C[.](#2.3.sentence-1)

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

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

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16201)

*Effects*: Initializes *current_* with std​::​move(current),*end_* with ranges​::​end(parent->*base_*),*stride_* with parent->*stride_*, and*missing_* with missing[.](#3.sentence-1)

[ð](#lib:stride_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>>;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16217)

*Effects*: Initializes *current_* with std​::​move(i.*current_*),*end_* with std​::​move(i.*end_*),*stride_* with i.*stride_*, and*missing_* with i.*missing_*[.](#4.sentence-1)

[ð](#lib:base,stride_view::iterator)

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

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16231)

*Returns*: std​::​move(*current_*)[.](#5.sentence-1)

[ð](#lib:base,stride_view::iterator_)

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

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16242)

*Returns*: *current_*[.](#6.sentence-1)

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

`constexpr iterator& operator++();
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16253)

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

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16257)

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

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

`constexpr void operator++(int);
`

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16272)

*Effects*: Equivalent to ++*this;

[ð](#lib:operator++,stride_view::iterator__)

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

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16283)

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

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

`constexpr iterator& operator--() 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#L16299)

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

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

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

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16315)

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

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

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

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16331)

*Preconditions*: If n is positive,ranges​::​distance(*current_*, *end_*) > *stride_* * (n - 1) is true[.](#13.sentence-1)

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

If n is negative, the *Effects* paragraph implies a precondition[.](#13.sentence-2)

â *end note*]

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16340)

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

[ð](#lib:operator-=,stride_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>;
`

[15](#15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16362)

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

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

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

[16](#16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16373)

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

[ð](#lib:operator==,stride_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<Base>>;
`

[17](#17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16385)

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

[ð](#lib:operator%3c,stride_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#L16397)

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

[ð](#lib:operator%3e,stride_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#L16409)

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

[ð](#lib:operator%3c=,stride_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#L16421)

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

[ð](#lib:operator%3e=,stride_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#L16433)

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

[ð](#lib:operator%3c=%3e,stride_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#L16445)

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

[ð](#lib:operator+,stride_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#L16459)

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

[ð](#lib:operator-,stride_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#L16476)

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

[ð](#lib:operator-,stride_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#L16493)

*Returns*: Let N be (x.*current_* - y.*current_*)[.](#25.sentence-1)

- [(25.1)](#25.1)

  If *Base* models [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]"),(N + x.*missing_* - y.*missing_*) / x.*stride_*[.](#25.1.sentence-1)

- [(25.2)](#25.2)

  Otherwise, if N is negative, -*div-ceil*(-N, x.*stride_*)[.](#25.2.sentence-1)

- [(25.3)](#25.3)

  Otherwise, *div-ceil*(N, x.*stride_*)[.](#25.3.sentence-1)

[ð](#lib:operator-,stride_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#L16514)

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

[ð](#lib:operator-,stride_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#L16526)

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

[ð](#lib:iter_move,stride_view::iterator)

`friend constexpr range_rvalue_reference_t<Base> iter_move(const iterator& i)
  noexcept(noexcept(ranges::iter_move(i.current_)));
`

[28](#28)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16538)

*Effects*: Equivalent to: return ranges​::​iter_move(i.*current_*);

[ð](#lib:iter_swap,stride_view::iterator)

`friend constexpr void iter_swap(const iterator& x, const iterator& y)
  noexcept(noexcept(ranges::iter_swap(x.current_, y.current_)))
  requires [indirectly_swappable](alg.req.ind.swap#concept:indirectly_swappable "24.3.7.4 Concept indirectly_­swappable [alg.req.ind.swap]")<iterator_t<Base>>;
`

[29](#29)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L16551)

*Effects*: Equivalent to:ranges​::​iter_swap(x.*current_*, y.*current_*);
