depish/cppdraft_translate
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
main
cppdraft_translate/cppdraft/range/factories.md
Leonov Artur (Depish) 043225d523 Init
2025-10-25 03:02:53 +03:00

1271 lines
63 KiB
Markdown
Raw Permalink Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

[range.factories]
# 25 Ranges library [[ranges]](./#ranges)
## 25.6 Range factories [range.factories]
### [25.6.1](#general) General [[range.factories.general]](range.factories.general)
[1](#general-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2580)
Subclause [range.factories] defines [*range factories*](#def:range_factories),
which are utilities to create a view[.](#general-1.sentence-1)
[2](#general-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2584)
Range factories are declared in namespace std​::​ranges​::​views[.](#general-2.sentence-1)
### [25.6.2](#range.empty) Empty view [[range.empty]](range.empty)
#### [25.6.2.1](#range.empty.overview) Overview [[range.empty.overview]](range.empty.overview)
[1](#range.empty.overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2591)
empty_view produces a view of no elements of
a particular type[.](#range.empty.overview-1.sentence-1)
[2](#range.empty.overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2595)
[*Example [1](#range.empty.overview-example-1)*: auto e = views::empty<int>;static_assert(ranges::empty(e));static_assert(0 == e.size()); — *end example*]
#### [25.6.2.2](#range.empty.view) Class template empty_view [[range.empty.view]](range.empty.view)
[🔗](#lib:empty_view)
namespace std::ranges {template<class T>requires is_object_v<T>class empty_view : public view_interface<empty_view<T>> {public:static constexpr T* begin() noexcept { return nullptr; }static constexpr T* end() noexcept { return nullptr; }static constexpr T* data() noexcept { return nullptr; }static constexpr size_t size() noexcept { return 0; }static constexpr bool empty() noexcept { return true; }};}
### [25.6.3](#range.single) Single view [[range.single]](range.single)
#### [25.6.3.1](#range.single.overview) Overview [[range.single.overview]](range.single.overview)
[1](#range.single.overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2626)
single_view produces a view that contains
exactly one element of a specified value[.](#range.single.overview-1.sentence-1)
[2](#range.single.overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2630)
The name views​::​single denotes a
customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#range.single.overview-2.sentence-1)
Given a subexpression E, the expressionviews​::​single(E) is expression-equivalent tosingle_view<decay_t<decltype((E))>>(E)[.](#range.single.overview-2.sentence-2)
[3](#range.single.overview-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2638)
[*Example [1](#range.single.overview-example-1)*: for (int i : views::single(4)) cout << i; // prints 4 — *end example*]
#### [25.6.3.2](#range.single.view) Class template single_view [[range.single.view]](range.single.view)
[🔗](#lib:single_view)
namespace std::ranges {template<[move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_­constructible [concept.moveconstructible]") T>requires is_object_v<T>class single_view : public view_interface<single_view<T>> {private:*movable-box*<T> *value_*; // *exposition only* (see [[range.move.wrap]](range.move.wrap "25.7.3 Movable wrapper"))public: single_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<T> = default; constexpr explicit single_view(const T& t) requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>; constexpr explicit single_view(T&& t); template<class... Args>requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<T, Args...>constexpr explicit single_view(in_place_t, Args&&... args); constexpr T* begin() noexcept; constexpr const T* begin() const noexcept; constexpr T* end() noexcept; constexpr const T* end() const noexcept; static constexpr bool empty() noexcept; static constexpr size_t size() noexcept; constexpr T* data() noexcept; constexpr const T* data() const noexcept; }; template<class T> single_view(T) -> single_view<T>;}
[🔗](#lib:single_view,constructor)
`constexpr explicit single_view(const T& t) requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>;
`
[1](#range.single.view-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2686)
*Effects*: Initializes *value_* with t[.](#range.single.view-1.sentence-1)
[🔗](#lib:single_view,constructor_)
`constexpr explicit single_view(T&& t);
`
[2](#range.single.view-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2697)
*Effects*: Initializes *value_* with std​::​move(t)[.](#range.single.view-2.sentence-1)
[🔗](#lib:single_view,constructor__)
`template<class... Args>
requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<T, Args...>
constexpr explicit single_view(in_place_t, Args&&... args);
`
[3](#range.single.view-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2710)
*Effects*: Initializes *value_* as if by*value_*{in_place, std​::​forward<Args>(args)...}[.](#range.single.view-3.sentence-1)
[🔗](#lib:begin,single_view)
`constexpr T* begin() noexcept;
constexpr const T* begin() const noexcept;
`
[4](#range.single.view-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2723)
*Effects*: Equivalent to: return data();
[🔗](#lib:end,single_view)
`constexpr T* end() noexcept;
constexpr const T* end() const noexcept;
`
[5](#range.single.view-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2735)
*Effects*: Equivalent to: return data() + 1;
[🔗](#lib:empty,single_view)
`static constexpr bool empty() noexcept;
`
[6](#range.single.view-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2746)
*Effects*: Equivalent to: return false;
[🔗](#lib:size,single_view)
`static constexpr size_t size() noexcept;
`
[7](#range.single.view-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2757)
*Effects*: Equivalent to: return 1;
[🔗](#lib:data,single_view)
`constexpr T* data() noexcept;
constexpr const T* data() const noexcept;
`
[8](#range.single.view-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2769)
*Effects*: Equivalent to: return *value_*.operator->();
### [25.6.4](#range.iota) Iota view [[range.iota]](range.iota)
#### [25.6.4.1](#range.iota.overview) Overview [[range.iota.overview]](range.iota.overview)
[1](#range.iota.overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2778)
iota_view generates a
sequence of elements by repeatedly incrementing an initial value[.](#range.iota.overview-1.sentence-1)
[2](#range.iota.overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2782)
The name views​::​iota denotes a
customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#range.iota.overview-2.sentence-1)
Given subexpressions E and F, the expressionsviews​::​iota(E) and views​::​iota(E, F) are expression-equivalent toiota_view<decay_t<decltype((E))>>(E) and iota_view(E, F),
respectively[.](#range.iota.overview-2.sentence-2)
[3](#range.iota.overview-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2792)
[*Example [1](#range.iota.overview-example-1)*: for (int i : views::iota(1, 10)) cout << i << ' '; // prints 1 2 3 4 5 6 7 8 9 — *end example*]
[4](#range.iota.overview-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2800)
The name views​::​indices denotes a
customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#range.iota.overview-4.sentence-1)
Given subexpression E,
let T be remove_cvref_t<decltype((E))>[.](#range.iota.overview-4.sentence-2)
views​::​indices(E) is expression-equivalent toviews​::​iota(T(0), E) if *is-integer-like*<T> is true,
and ill-formed otherwise[.](#range.iota.overview-4.sentence-3)
#### [25.6.4.2](#range.iota.view) Class template iota_view [[range.iota.view]](range.iota.view)
[🔗](#lib:iota_view)
namespace std::ranges {template<class I>concept [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") = *see below*; // *exposition only*template<class I>concept [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") = *see below*; // *exposition only*template<[weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]") W, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound = unreachable_sentinel_t>requires [*weakly-equality-comparable-with*](concept.equalitycomparable#concept:weakly-equality-comparable-with "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<W, Bound> && [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<W>class iota_view : public view_interface<iota_view<W, Bound>> {private:// [[range.iota.iterator]](#range.iota.iterator "25.6.4.3 Class iota_­view​::​iterator"), class iota_view​::​*iterator*struct *iterator*; // *exposition only*// [[range.iota.sentinel]](#range.iota.sentinel "25.6.4.4 Class iota_­view​::​sentinel"), class iota_view​::​*sentinel*struct *sentinel*; // *exposition only* W *value_* = W(); // *exposition only* Bound *bound_* = Bound(); // *exposition only*public: iota_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<W> = default; constexpr explicit iota_view(W value); constexpr explicit iota_view(type_identity_t<W> value, type_identity_t<Bound> bound); constexpr explicit iota_view(*iterator* first, *see below* last); constexpr *iterator* begin() const; constexpr auto end() const; constexpr *iterator* end() const requires [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound>; constexpr bool empty() const; constexpr auto size() const requires *see below*; }; template<class W, class Bound>requires (!*is-integer-like*<W> || !*is-integer-like*<Bound> ||(*is-signed-integer-like*<W> == *is-signed-integer-like*<Bound>)) iota_view(W, Bound) -> iota_view<W, Bound>;}
[1](#range.iota.view-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2856)
Let *IOTA-DIFF-T*(W) be defined as follows:
- [(1.1)](#range.iota.view-1.1)
If W is not an integral type, or
if it is an integral type and sizeof(iter_difference_t<W>) is greater than sizeof(W),
then *IOTA-DIFF-T*(W) denotes iter_difference_t<W>[.](#range.iota.view-1.1.sentence-1)
- [(1.2)](#range.iota.view-1.2)
Otherwise, *IOTA-DIFF-T*(W) is a signed integer type of width greater than the width of W if such a type exists[.](#range.iota.view-1.2.sentence-1)
- [(1.3)](#range.iota.view-1.3)
Otherwise, *IOTA-DIFF-T*(W) is an unspecified signed-integer-like type ([[iterator.concept.winc]](iterator.concept.winc "24.3.4.4 Concept weakly_­incrementable"))
of width not less than the width of W[.](#range.iota.view-1.3.sentence-1)
[*Note [1](#range.iota.view-note-1)*:
It is unspecified
whether this type satisfies [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]")[.](#range.iota.view-1.3.sentence-2)
— *end note*]
[2](#range.iota.view-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2878)
The exposition-only [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") concept is equivalent to:
[🔗](#concept:decrementable)
`template<class I>
concept [decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") = // exposition only
[incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]")<I> && requires(I i) {
{ --i } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
{ i-- } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I>;
};
`
[3](#range.iota.view-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2890)
When an object is in the domain of both pre- and post-decrement,
the object is said to be [*decrementable*](#def:decrementable)[.](#range.iota.view-3.sentence-1)
[4](#range.iota.view-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2894)
Let a and b be equal objects of type I[.](#range.iota.view-4.sentence-1)
I models [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]") only if
- [(4.1)](#range.iota.view-4.1)
If a and b are decrementable,
then the following are all true:
* [(4.1.1)](#range.iota.view-4.1.1)
addressof(--a) == addressof(a)
* [(4.1.2)](#range.iota.view-4.1.2)
bool(a-- == b)
* [(4.1.3)](#range.iota.view-4.1.3)
bool(((void)a--, a) == --b)
* [(4.1.4)](#range.iota.view-4.1.4)
bool(++(--a) == b)[.](#range.iota.view-4.1.sentence-1)
- [(4.2)](#range.iota.view-4.2)
If a and b are incrementable,
then bool(--(++a) == b)[.](#range.iota.view-4.2.sentence-1)
[5](#range.iota.view-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2911)
The exposition-only [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") concept is equivalent to:
[🔗](#concept:advanceable)
`template<class I>
concept [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") = // exposition only
[decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<I> && [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<I> &&
requires(I i, const I j, const IOTA-DIFF-T(I) n) {
{ i += n } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
{ i -= n } -> [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<I&>;
I(j + n);
I(n + j);
I(j - n);
{ j - j } -> [convertible_to](concept.convertible#concept:convertible_to "18.4.4 Concept convertible_­to [concept.convertible]")<IOTA-DIFF-T(I)>;
};
`
Let D be *IOTA-DIFF-T*(I)[.](#range.iota.view-sentence-1)
Let a and b be objects of type I such thatb is reachable from a after n applications of ++a,
for some value n of type D[.](#range.iota.view-sentence-2)
I models [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]") only if
- (a += n) is equal to b[.](#range.iota.view-sentence-1)
- addressof(a += n) is equal to addressof(a)[.](#range.iota.view-sentence-1)
- I(a + n) is equal to (a += n)[.](#range.iota.view-sentence-1)
- For any two positive values x and y of type D,
if I(a + D(x + y)) is well-defined, then I(a + D(x + y)) is equal to I(I(a + x) + y)[.](#range.iota.view-sentence-1)
- I(a + D(0)) is equal to a[.](#range.iota.view-sentence-1)
- If I(a + D(n - 1)) is well-defined, then I(a + n) is equal to [](I c) { return ++c; }(I(a + D(n - 1)))[.](#range.iota.view-sentence-1)
- (b += -n) is equal to a[.](#range.iota.view-sentence-1)
- (b -= n) is equal to a[.](#range.iota.view-sentence-1)
- addressof(b -= n) is equal to addressof(b)[.](#range.iota.view-sentence-1)
- I(b - n) is equal to (b -= n)[.](#range.iota.view-sentence-1)
- D(b - a) is equal to n[.](#range.iota.view-sentence-1)
- D(a - b) is equal to D(-n)[.](#range.iota.view-sentence-1)
- bool(a <= b) is true[.](#range.iota.view-sentence-1)
[🔗](#lib:iota_view,constructor)
`constexpr explicit iota_view(W value);
`
[6](#range.iota.view-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2959)
*Preconditions*: Bound denotes unreachable_sentinel_t orBound() is reachable from value[.](#range.iota.view-6.sentence-1)
When W and Bound model [totally_ordered_with](concept.totallyordered#concept:totally_ordered_with "18.5.5 Concept totally_­ordered [concept.totallyordered]"),
then bool(value <= Bound()) is true[.](#range.iota.view-6.sentence-2)
[7](#range.iota.view-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2966)
*Effects*: Initializes *value_* with value[.](#range.iota.view-7.sentence-1)
[🔗](#lib:iota_view,constructor_)
`constexpr explicit iota_view(type_identity_t<W> value, type_identity_t<Bound> bound);
`
[8](#range.iota.view-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2977)
*Preconditions*: Bound denotes unreachable_sentinel_t orbound is reachable from value[.](#range.iota.view-8.sentence-1)
When W and Bound model [totally_ordered_with](concept.totallyordered#concept:totally_ordered_with "18.5.5 Concept totally_­ordered [concept.totallyordered]"),
then bool(value <= bound) is true[.](#range.iota.view-8.sentence-2)
[9](#range.iota.view-9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2984)
*Effects*: Initializes *value_* with value and*bound_* with bound[.](#range.iota.view-9.sentence-1)
[🔗](#lib:iota_view,constructor__)
`constexpr explicit iota_view(iterator first, see below last);
`
[10](#range.iota.view-10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2996)
*Effects*: Equivalent to:
- [(10.1)](#range.iota.view-10.1)
If [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> is true,iota_view(first.*value_*, last.*value_*)[.](#range.iota.view-10.1.sentence-1)
- [(10.2)](#range.iota.view-10.2)
Otherwise, if Bound denotes unreachable_sentinel_t,iota_view(first.*value_*, last)[.](#range.iota.view-10.2.sentence-1)
- [(10.3)](#range.iota.view-10.3)
Otherwise, iota_view(first.*value_*, last.*bound_*)[.](#range.iota.view-10.3.sentence-1)
[11](#range.iota.view-11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3010)
*Remarks*: The type of last is:
- [(11.1)](#range.iota.view-11.1)
If [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> is true, *iterator*[.](#range.iota.view-11.1.sentence-1)
- [(11.2)](#range.iota.view-11.2)
Otherwise, if Bound denotes unreachable_sentinel_t,Bound[.](#range.iota.view-11.2.sentence-1)
- [(11.3)](#range.iota.view-11.3)
Otherwise, *sentinel*[.](#range.iota.view-11.3.sentence-1)
[🔗](#lib:begin,iota_view)
`constexpr iterator begin() const;
`
[12](#range.iota.view-12)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3030)
*Effects*: Equivalent to: return *iterator*{*value_*};
[🔗](#lib:end,iota_view)
`constexpr auto end() const;
`
[13](#range.iota.view-13)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3041)
*Effects*: Equivalent to:if constexpr ([same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>)return unreachable_sentinel;elsereturn *sentinel*{*bound_*};
[🔗](#lib:end,iota_view_)
`constexpr iterator end() const requires [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound>;
`
[14](#range.iota.view-14)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3058)
*Effects*: Equivalent to: return *iterator*{*bound_*};
[🔗](#lib:empty,iota_view)
`constexpr bool empty() const;
`
[15](#range.iota.view-15)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3069)
*Effects*: Equivalent to: return *value_* == *bound_*;
[🔗](#lib:size,iota_view)
`constexpr auto size() const requires see below;
`
[16](#range.iota.view-16)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3080)
*Effects*: Equivalent to:if constexpr (*is-integer-like*<W> && *is-integer-like*<Bound>)return (*value_* < 0)? ((*bound_* < 0)? *to-unsigned-like*(-*value_*) - *to-unsigned-like*(-*bound_*): *to-unsigned-like*(*bound_*) + *to-unsigned-like*(-*value_*)): *to-unsigned-like*(*bound_*) - *to-unsigned-like*(*value_*);elsereturn *to-unsigned-like*(*bound_* - *value_*);
[17](#range.iota.view-17)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3094)
*Remarks*: The expression in the [*requires-clause*](temp.pre#nt:requires-clause "13.1 Preamble [temp.pre]") is equivalent to:([same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<W, Bound> && [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>) || (*is-integer-like*<W> && *is-integer-like*<Bound>) ||[sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<Bound, W>
#### [25.6.4.3](#range.iota.iterator) Class iota_view​::​*iterator* [[range.iota.iterator]](range.iota.iterator)
[🔗](#lib:iota_view::iterator)
namespace std::ranges {template<[weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]") W, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound>requires [*weakly-equality-comparable-with*](concept.equalitycomparable#concept:weakly-equality-comparable-with "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<W, Bound> && [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<W>struct iota_view<W, Bound>::*iterator* {private: W *value_* = W(); // *exposition only*public:using iterator_concept = *see below*; using iterator_category = input_iterator_tag; // present only if W models [incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]") and// *IOTA-DIFF-T*(W) is an integral typeusing value_type = W; using difference_type = *IOTA-DIFF-T*(W); *iterator*() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<W> = default; constexpr explicit *iterator*(W value); constexpr W operator*() const noexcept(is_nothrow_copy_constructible_v<W>); constexpr *iterator*& operator++(); constexpr void operator++(int); constexpr *iterator* operator++(int) requires [incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]")<W>; constexpr *iterator*& operator--() requires [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; constexpr *iterator* operator--(int) requires [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; constexpr *iterator*& operator+=(difference_type n)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; constexpr *iterator*& operator-=(difference_type n)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; constexpr W operator[](difference_type n) constrequires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; 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]")<W>; friend constexpr bool operator<(const *iterator*& x, const *iterator*& y)requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>; friend constexpr bool operator>(const *iterator*& x, const *iterator*& y)requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>; friend constexpr bool operator<=(const *iterator*& x, const *iterator*& y)requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>; friend constexpr bool operator>=(const *iterator*& x, const *iterator*& y)requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>; friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y)requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W> && [three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<W>; friend constexpr *iterator* operator+(*iterator* i, difference_type n)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; friend constexpr *iterator* operator+(difference_type n, *iterator* i)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; friend constexpr *iterator* operator-(*iterator* i, difference_type n)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; friend constexpr difference_type operator-(const *iterator*& x, const *iterator*& y)requires [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>; };}
[1](#range.iota.iterator-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3167)
*iterator*​::​iterator_concept is defined as follows:
- [(1.1)](#range.iota.iterator-1.1)
If W models [*advanceable*](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]"), theniterator_concept is random_access_iterator_tag[.](#range.iota.iterator-1.1.sentence-1)
- [(1.2)](#range.iota.iterator-1.2)
Otherwise, if W models [*decrementable*](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]"), theniterator_concept is bidirectional_iterator_tag[.](#range.iota.iterator-1.2.sentence-1)
- [(1.3)](#range.iota.iterator-1.3)
Otherwise, if W models [incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]"), theniterator_concept is forward_iterator_tag[.](#range.iota.iterator-1.3.sentence-1)
- [(1.4)](#range.iota.iterator-1.4)
Otherwise, iterator_concept is input_iterator_tag[.](#range.iota.iterator-1.4.sentence-1)
[2](#range.iota.iterator-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3179)
[*Note [1](#range.iota.iterator-note-1)*:
Overloads for iter_move and iter_swap are omitted intentionally[.](#range.iota.iterator-2.sentence-1)
— *end note*]
[🔗](#lib:iota_view::iterator,constructor)
`constexpr explicit iterator(W value);
`
[3](#range.iota.iterator-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3190)
*Effects*: Initializes *value_* with value[.](#range.iota.iterator-3.sentence-1)
[🔗](#lib:operator*,iota_view::iterator)
`constexpr W operator*() const noexcept(is_nothrow_copy_constructible_v<W>);
`
[4](#range.iota.iterator-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3201)
*Effects*: Equivalent to: return *value_*;
[5](#range.iota.iterator-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3205)
[*Note [2](#range.iota.iterator-note-2)*:
The noexcept clause is needed by the default iter_move implementation[.](#range.iota.iterator-5.sentence-1)
— *end note*]
[🔗](#lib:operator++,iota_view::iterator)
`constexpr iterator& operator++();
`
[6](#range.iota.iterator-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3218)
*Effects*: Equivalent to:++*value_*;return *this;
[🔗](#lib:operator++,iota_view::iterator_)
`constexpr void operator++(int);
`
[7](#range.iota.iterator-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3233)
*Effects*: Equivalent to ++*this[.](#range.iota.iterator-7.sentence-1)
[🔗](#lib:operator++,iota_view::iterator__)
`constexpr iterator operator++(int) requires [incrementable](iterator.concept.inc#concept:incrementable "24.3.4.5 Concept incrementable [iterator.concept.inc]")<W>;
`
[8](#range.iota.iterator-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3244)
*Effects*: Equivalent to:auto tmp = *this;++*this;return tmp;
[🔗](#lib:operator--,iota_view::iterator)
`constexpr iterator& operator--() requires [decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[9](#range.iota.iterator-9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3260)
*Effects*: Equivalent to:--*value_*;return *this;
[🔗](#lib:operator--,iota_view::iterator_)
`constexpr iterator operator--(int) requires [decrementable](#concept:decrementable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[10](#range.iota.iterator-10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3275)
*Effects*: Equivalent to:auto tmp = *this;--*this;return tmp;
[🔗](#lib:operator+=,iota_view::iterator)
`constexpr iterator& operator+=(difference_type n)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[11](#range.iota.iterator-11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3292)
*Effects*: Equivalent to:if constexpr (*is-integer-like*<W> && !*is-signed-integer-like*<W>) {if (n >= difference_type(0))*value_* += static_cast<W>(n); else*value_* -= static_cast<W>(-n);} else {*value_* += n;}return *this;
[🔗](#lib:operator-=,iota_view::iterator)
`constexpr iterator& operator-=(difference_type n)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[12](#range.iota.iterator-12)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3315)
*Effects*: Equivalent to:if constexpr (*is-integer-like*<W> && !*is-signed-integer-like*<W>) {if (n >= difference_type(0))*value_* -= static_cast<W>(n); else*value_* += static_cast<W>(-n);} else {*value_* -= n;}return *this;
[🔗](#lib:operator%5b%5d,iota_view::iterator)
`constexpr W operator[](difference_type n) const
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[13](#range.iota.iterator-13)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3338)
*Effects*: Equivalent to: return W(*value_* + n);
[🔗](#lib:operator==,iota_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]")<W>;
`
[14](#range.iota.iterator-14)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3350)
*Effects*: Equivalent to: return x.*value_* == y.*value_*;
[🔗](#lib:operator%3c,iota_view::iterator)
`friend constexpr bool operator<(const iterator& x, const iterator& y)
requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>;
`
[15](#range.iota.iterator-15)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3362)
*Effects*: Equivalent to: return x.*value_* < y.*value_*;
[🔗](#lib:operator%3e,iota_view::iterator)
`friend constexpr bool operator>(const iterator& x, const iterator& y)
requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>;
`
[16](#range.iota.iterator-16)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3374)
*Effects*: Equivalent to: return y < x;
[🔗](#lib:operator%3c=,iota_view::iterator)
`friend constexpr bool operator<=(const iterator& x, const iterator& y)
requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>;
`
[17](#range.iota.iterator-17)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3386)
*Effects*: Equivalent to: return !(y < x);
[🔗](#lib:operator%3e=,iota_view::iterator)
`friend constexpr bool operator>=(const iterator& x, const iterator& y)
requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W>;
`
[18](#range.iota.iterator-18)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3398)
*Effects*: Equivalent to: return !(x < y);
[🔗](#lib:operator%3c=%3e,iota_view::iterator)
`friend constexpr auto operator<=>(const iterator& x, const iterator& y)
requires [totally_ordered](concept.totallyordered#concept:totally_ordered "18.5.5 Concept totally_­ordered [concept.totallyordered]")<W> && [three_way_comparable](cmp.concept#concept:three_way_comparable "17.12.4 Concept three_­way_­comparable [cmp.concept]")<W>;
`
[19](#range.iota.iterator-19)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3410)
*Effects*: Equivalent to: return x.*value_* <=> y.*value_*;
[🔗](#lib:operator+,iota_view::iterator)
`friend constexpr iterator operator+(iterator i, difference_type n)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[20](#range.iota.iterator-20)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3422)
*Effects*: Equivalent to:i += n;return i;
[🔗](#lib:operator+,iota_view::iterator_)
`friend constexpr iterator operator+(difference_type n, iterator i)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[21](#range.iota.iterator-21)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3438)
*Effects*: Equivalent to: return i + n;
[🔗](#lib:operator-,iota_view::iterator)
`friend constexpr iterator operator-(iterator i, difference_type n)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[22](#range.iota.iterator-22)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3450)
*Effects*: Equivalent to:i -= n;return i;
[🔗](#lib:operator-,iota_view::iterator_)
`friend constexpr difference_type operator-(const iterator& x, const iterator& y)
requires [advanceable](#concept:advanceable "25.6.4.2 Class template iota_­view [range.iota.view]")<W>;
`
[23](#range.iota.iterator-23)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3466)
*Effects*: Equivalent to:using D = difference_type;if constexpr (*is-integer-like*<W>) {if constexpr (*is-signed-integer-like*<W>)return D(D(x.*value_*) - D(y.*value_*)); elsereturn (y.*value_* > x.*value_*)? D(-D(y.*value_* - x.*value_*)): D(x.*value_* - y.*value_*);} else {return x.*value_* - y.*value_*;}
#### [25.6.4.4](#range.iota.sentinel) Class iota_view​::​*sentinel* [[range.iota.sentinel]](range.iota.sentinel)
[🔗](#lib:iota_view::sentinel)
namespace std::ranges {template<[weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]") W, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound>requires [*weakly-equality-comparable-with*](concept.equalitycomparable#concept:weakly-equality-comparable-with "18.5.4 Concept equality_­comparable [concept.equalitycomparable]")<W, Bound> && [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<W>struct iota_view<W, Bound>::*sentinel* {private: Bound *bound_* = Bound(); // *exposition only*public:*sentinel*() = default; constexpr explicit *sentinel*(Bound bound); friend constexpr bool operator==(const *iterator*& x, const *sentinel*& y); friend constexpr iter_difference_t<W> operator-(const *iterator*& x, const *sentinel*& y)requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<Bound, W>; friend constexpr iter_difference_t<W> operator-(const *sentinel*& 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]")<Bound, W>; };}
[🔗](#lib:iota_view::sentinel,constructor)
`constexpr explicit sentinel(Bound bound);
`
[1](#range.iota.sentinel-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3515)
*Effects*: Initializes *bound_* with bound[.](#range.iota.sentinel-1.sentence-1)
[🔗](#lib:operator==,iota_view::sentinel)
`friend constexpr bool operator==(const iterator& x, const sentinel& y);
`
[2](#range.iota.sentinel-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3526)
*Effects*: Equivalent to: return x.*value_* == y.*bound_*;
[🔗](#lib:operator-,iota_view::sentinel)
`friend constexpr iter_difference_t<W> operator-(const iterator& x, const sentinel& y)
requires [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<Bound, W>;
`
[3](#range.iota.sentinel-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3538)
*Effects*: Equivalent to: return x.*value_* - y.*bound_*;
[🔗](#lib:operator-,iota_view::sentinel_)
`friend constexpr iter_difference_t<W> operator-(const sentinel& 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]")<Bound, W>;
`
[4](#range.iota.sentinel-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3550)
*Effects*: Equivalent to: return -(y - x);
### [25.6.5](#range.repeat) Repeat view [[range.repeat]](range.repeat)
#### [25.6.5.1](#range.repeat.overview) Overview [[range.repeat.overview]](range.repeat.overview)
[1](#range.repeat.overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3559)
repeat_view generates a sequence of elements
by repeatedly producing the same value[.](#range.repeat.overview-1.sentence-1)
[2](#range.repeat.overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3563)
The name views​::​repeat denotes
a customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#range.repeat.overview-2.sentence-1)
Given subexpressions E and F,
the expressions views​::​repeat(E) and views​::​repeat(E, F) are expression-equivalent torepeat_view<decay_t<decltype((E))>>(E) and repeat_view(E, F), respectively[.](#range.repeat.overview-2.sentence-2)
[3](#range.repeat.overview-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3572)
[*Example [1](#range.repeat.overview-example-1)*: for (int i : views::repeat(17, 4)) cout << i << ' ';// prints 17 17 17 17 — *end example*]
#### [25.6.5.2](#range.repeat.view) Class template repeat_view [[range.repeat.view]](range.repeat.view)
namespace std::ranges {template<class T>concept [*integer-like-with-usable-difference-type*](#concept:integer-like-with-usable-difference-type "25.6.5.2 Class template repeat_­view [range.repeat.view]") = // *exposition only**is-signed-integer-like*<T> || (*is-integer-like*<T> && [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_­incrementable [iterator.concept.winc]")<T>); template<[move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_­constructible [concept.moveconstructible]") T, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound = unreachable_sentinel_t>requires (is_object_v<T> && [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<T, remove_cv_t<T>> &&([*integer-like-with-usable-difference-type*](#concept:integer-like-with-usable-difference-type "25.6.5.2 Class template repeat_­view [range.repeat.view]")<Bound> ||[same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>))class [repeat_view](#lib:repeat_view "25.6.5.2 Class template repeat_­view [range.repeat.view]") : public view_interface<repeat_view<T, Bound>> {private:// [[range.repeat.iterator]](#range.repeat.iterator "25.6.5.3 Class repeat_­view​::​iterator"), class repeat_view​::​*iterator*struct *iterator*; // *exposition only**movable-box*<T> *value_*; // *exposition only*, see [[range.move.wrap]](range.move.wrap "25.7.3 Movable wrapper") Bound *bound_* = Bound(); // *exposition only*public: repeat_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<T> = default; constexpr explicit repeat_view(const T& value, Bound bound = Bound())requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>; constexpr explicit repeat_view(T&& value, Bound bound = Bound()); template<class... TArgs, class... BoundArgs>requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<T, TArgs...> &&[constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<Bound, BoundArgs...>constexpr explicit repeat_view(piecewise_construct_t,
tuple<TArgs...> value_args, tuple<BoundArgs...> bound_args = tuple<>{}); constexpr *iterator* begin() const; constexpr *iterator* end() const requires (![same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>); constexpr unreachable_sentinel_t end() const noexcept; constexpr auto size() const requires (![same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>); }; template<class T, class Bound = unreachable_sentinel_t> repeat_view(T, Bound = Bound()) -> repeat_view<T, Bound>;}
[🔗](#lib:repeat_view,constructor)
`constexpr explicit repeat_view(const T& value, Bound bound = Bound())
requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>;
`
[1](#range.repeat.view-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3632)
*Preconditions*: If Bound is not unreachable_sentinel_t,bound ≥ 0[.](#range.repeat.view-1.sentence-1)
[2](#range.repeat.view-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3637)
*Effects*: Initializes *value_* with value and*bound_* with bound[.](#range.repeat.view-2.sentence-1)
[🔗](#lib:repeat_view,constructor_)
`constexpr explicit repeat_view(T&& value, Bound bound = Bound());
`
[3](#range.repeat.view-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3649)
*Preconditions*: If Bound is not unreachable_sentinel_t, bound ≥ 0[.](#range.repeat.view-3.sentence-1)
[4](#range.repeat.view-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3653)
*Effects*: Initializes *value_* with std​::​move(value) and*bound_* with bound[.](#range.repeat.view-4.sentence-1)
[🔗](#lib:repeat_view,constructor__)
`template<class... TArgs, class... BoundArgs>
requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<T, TArgs...> &&
[constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<Bound, BoundArgs...>
constexpr explicit repeat_view(piecewise_construct_t,
tuple<TArgs...> value_args, tuple<BoundArgs...> bound_args = tuple<>{});
`
[5](#range.repeat.view-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3669)
*Effects*: Initializes *value_* withmake_from_tuple<T>(std​::​move(value_args)) and
initializes *bound_* withmake_from_tuple<Bound>(std​::​move(bound_args))[.](#range.repeat.view-5.sentence-1)
The behavior is undefined ifBound is not unreachable_sentinel_t and*bound_* is negative[.](#range.repeat.view-5.sentence-2)
[🔗](#lib:begin,repeat_view)
`constexpr iterator begin() const;
`
[6](#range.repeat.view-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3687)
*Effects*: Equivalent to: return *iterator*(addressof(**value_*));
[🔗](#lib:end,repeat_view)
`constexpr iterator end() const requires (![same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>);
`
[7](#range.repeat.view-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3698)
*Effects*: Equivalent to: return *iterator*(addressof(**value_*), *bound_*);
[🔗](#lib:end,repeat_view_)
`constexpr unreachable_sentinel_t end() const noexcept;
`
[8](#range.repeat.view-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3709)
*Effects*: Equivalent to: return unreachable_sentinel;
[🔗](#lib:size,repeat_view)
`constexpr auto size() const requires (![same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>);
`
[9](#range.repeat.view-9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3720)
*Effects*: Equivalent to: return *to-unsigned-like*(*bound_*);
#### [25.6.5.3](#range.repeat.iterator) Class repeat_view​::​*iterator* [[range.repeat.iterator]](range.repeat.iterator)
[🔗](#lib:repeat_view::iterator)
namespace std::ranges {template<[move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_­constructible [concept.moveconstructible]") T, [semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") Bound>requires (is_object_v<T> && [same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<T, remove_cv_t<T>> &&([*integer-like-with-usable-difference-type*](#concept:integer-like-with-usable-difference-type "25.6.5.2 Class template repeat_­view [range.repeat.view]")<Bound> ||[same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>))class repeat_view<T, Bound>::*iterator* {private:using *index-type* = // *exposition only* conditional_t<[same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<Bound, unreachable_sentinel_t>, ptrdiff_t, Bound>; const T* *value_* = nullptr; // *exposition only**index-type* *current_* = *index-type*(); // *exposition only*constexpr explicit *iterator*(const T* value, *index-type* b = *index-type*()); // *exposition only*public:using iterator_concept = random_access_iterator_tag; using iterator_category = random_access_iterator_tag; using value_type = T; using difference_type = *see below*; *iterator*() = default; constexpr const T& operator*() const noexcept; constexpr *iterator*& operator++(); constexpr *iterator* operator++(int); constexpr *iterator*& operator--(); constexpr *iterator* operator--(int); constexpr *iterator*& operator+=(difference_type n); constexpr *iterator*& operator-=(difference_type n); constexpr const T& operator[](difference_type n) const noexcept; friend constexpr bool operator==(const *iterator*& x, const *iterator*& y); friend constexpr auto operator<=>(const *iterator*& x, const *iterator*& y); friend constexpr *iterator* operator+(*iterator* i, difference_type n); friend constexpr *iterator* operator+(difference_type n, *iterator* i); friend constexpr *iterator* operator-(*iterator* i, difference_type n); friend constexpr difference_type operator-(const *iterator*& x, const *iterator*& y); };}
[1](#range.repeat.iterator-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3775)
If *is-signed-integer-like*<*index-type*> is true,
the member [*typedef-name*](dcl.typedef#nt:typedef-name "9.2.4 The typedef specifier [dcl.typedef]") difference_type denotes *index-type*[.](#range.repeat.iterator-1.sentence-1)
Otherwise, it denotes *IOTA-DIFF-T*(*index-type*) ([[range.iota.view]](#range.iota.view "25.6.4.2 Class template iota_­view"))[.](#range.repeat.iterator-1.sentence-2)
[🔗](#lib:repeat_view::iterator,constructor)
`constexpr explicit iterator(const T* value, index-type b = index-type());
`
[2](#range.repeat.iterator-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3787)
*Preconditions*: If Bound is not unreachable_sentinel_t, b ≥ 0[.](#range.repeat.iterator-2.sentence-1)
[3](#range.repeat.iterator-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3791)
*Effects*: Initializes *value_* with value and*current_* with b[.](#range.repeat.iterator-3.sentence-1)
[🔗](#lib:operator*,repeat_view::iterator)
`constexpr const T& operator*() const noexcept;
`
[4](#range.repeat.iterator-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3803)
*Effects*: Equivalent to: return **value_*;
[🔗](#lib:operator++,repeat_view::iterator)
`constexpr iterator& operator++();
`
[5](#range.repeat.iterator-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3814)
*Effects*: Equivalent to:++*current_*;return *this;
[🔗](#lib:operator++,repeat_view::iterator_)
`constexpr iterator operator++(int);
`
[6](#range.repeat.iterator-6)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3829)
*Effects*: Equivalent to:auto tmp = *this;++*this;return tmp;
[🔗](#lib:operator--,repeat_view::iterator)
`constexpr iterator& operator--();
`
[7](#range.repeat.iterator-7)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3845)
*Preconditions*: If Bound is not unreachable_sentinel_t,current_>0[.](#range.repeat.iterator-7.sentence-1)
[8](#range.repeat.iterator-8)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3850)
*Effects*: Equivalent to:--*current_*;return *this;
[🔗](#lib:operator--,repeat_view::iterator_)
`constexpr iterator operator--(int);
`
[9](#range.repeat.iterator-9)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3865)
*Effects*: Equivalent to:auto tmp = *this;--*this;return tmp;
[🔗](#lib:operator+=,repeat_view::iterator)
`constexpr iterator& operator+=(difference_type n);
`
[10](#range.repeat.iterator-10)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3881)
*Preconditions*: If Bound is not unreachable_sentinel_t,current_+n≥0[.](#range.repeat.iterator-10.sentence-1)
[11](#range.repeat.iterator-11)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3886)
*Effects*: Equivalent to:*current_* += n;return *this;
[🔗](#lib:operator-=,repeat_view::iterator)
`constexpr iterator& operator-=(difference_type n);
`
[12](#range.repeat.iterator-12)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3901)
*Preconditions*: If Bound is not unreachable_sentinel_t,current_−n≥0[.](#range.repeat.iterator-12.sentence-1)
[13](#range.repeat.iterator-13)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3906)
*Effects*: Equivalent to:*current_* -= n;return *this;
[🔗](#lib:operator%5b%5d,repeat_view::iterator)
`constexpr const T& operator[](difference_type n) const noexcept;
`
[14](#range.repeat.iterator-14)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3921)
*Effects*: Equivalent to: return *(*this + n);
[🔗](#lib:operator==,repeat_view::iterator)
`friend constexpr bool operator==(const iterator& x, const iterator& y);
`
[15](#range.repeat.iterator-15)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3932)
*Effects*: Equivalent to: return x.*current_* == y.*current_*;
[🔗](#lib:operator%3c=%3e,repeat_view::iterator)
`friend constexpr auto operator<=>(const iterator& x, const iterator& y);
`
[16](#range.repeat.iterator-16)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3943)
*Effects*: Equivalent to: return x.*current_* <=> y.*current_*;
[🔗](#lib:operator+,repeat_view::iterator)
`friend constexpr iterator operator+(iterator i, difference_type n);
friend constexpr iterator operator+(difference_type n, iterator i);
`
[17](#range.repeat.iterator-17)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3955)
*Effects*: Equivalent to:i += n;return i;
[🔗](#lib:operator-,repeat_view::iterator)
`friend constexpr iterator operator-(iterator i, difference_type n);
`
[18](#range.repeat.iterator-18)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3970)
*Effects*: Equivalent to:i -= n;return i;
[🔗](#lib:operator-,repeat_view::iterator_)
`friend constexpr difference_type operator-(const iterator& x, const iterator& y);
`
[19](#range.repeat.iterator-19)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3985)
*Effects*: Equivalent to:return static_cast<difference_type>(x.*current_*) - static_cast<difference_type>(y.*current_*);
### [25.6.6](#range.istream) Istream view [[range.istream]](range.istream)
#### [25.6.6.1](#range.istream.overview) Overview [[range.istream.overview]](range.istream.overview)
[1](#range.istream.overview-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L3997)
basic_istream_view models [input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") and
reads (using operator>>) successive elements
from its corresponding input stream[.](#range.istream.overview-1.sentence-1)
[2](#range.istream.overview-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4002)
The name views​::​istream<T> denotes
a customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#range.istream.overview-2.sentence-1)
Given a type T and a subexpression E of type U,
if U models[derived_from](concept.derived#concept:derived_from "18.4.3 Concept derived_­from [concept.derived]")<basic_istream<typename U​::​char_type,typename U​::​traits_type>>,
then the expression views​::​istream<T>(E) is expression-equivalent tobasic_istream_view<T, typename U​::​char_type,typename U​::​traits_type>(E);
otherwise, views​::​istream<T>(E) is ill-formed[.](#range.istream.overview-2.sentence-2)
[3](#range.istream.overview-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4014)
[*Example [1](#range.istream.overview-example-1)*: auto ints = istringstream{"0 1 2 3 4"};
ranges::copy(views::istream<int>(ints), ostream_iterator<int>{cout, "-"});// prints 0-1-2-3-4- — *end example*]
#### [25.6.6.2](#range.istream.view) Class template basic_istream_view [[range.istream.view]](range.istream.view)
[🔗](#lib:basic_istream_view)
namespace std::ranges {template<class Val, class CharT, class Traits>concept [*stream-extractable*](#concept:stream-extractable "25.6.6.2 Class template basic_­istream_­view [range.istream.view]") = // *exposition only*requires(basic_istream<CharT, Traits>& is, Val& t) { is >> t; }; template<[movable](concepts.object#concept:movable "18.6 Object concepts [concepts.object]") Val, class CharT, class Traits = char_traits<CharT>>requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<Val> &&[*stream-extractable*](#concept:stream-extractable "25.6.6.2 Class template basic_­istream_­view [range.istream.view]")<Val, CharT, Traits>class basic_istream_view : public view_interface<basic_istream_view<Val, CharT, Traits>> {public:constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream); constexpr auto begin() {**stream_* >> *value_*; return *iterator*{*this}; }constexpr default_sentinel_t end() const noexcept; private:// [[range.istream.iterator]](#range.istream.iterator "25.6.6.3 Class basic_­istream_­view​::​iterator"), class basic_istream_view​::​*iterator*struct *iterator*; // *exposition only* basic_istream<CharT, Traits>* *stream_*; // *exposition only* Val *value_* = Val(); // *exposition only*};}
[🔗](#lib:basic_istream_view,constructor)
`constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream);
`
[1](#range.istream.view-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4063)
*Effects*: Initializes *stream_* with addressof(stream)[.](#range.istream.view-1.sentence-1)
[🔗](#lib:end,basic_istream_view)
`constexpr default_sentinel_t end() const noexcept;
`
[2](#range.istream.view-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4074)
*Effects*: Equivalent to: return default_sentinel;
#### [25.6.6.3](#range.istream.iterator) Class basic_istream_view​::​*iterator* [[range.istream.iterator]](range.istream.iterator)
[🔗](#lib:basic_istream_view::iterator)
namespace std::ranges {template<[movable](concepts.object#concept:movable "18.6 Object concepts [concepts.object]") Val, class CharT, class Traits>requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_­initializable [concept.default.init]")<Val> &&[*stream-extractable*](#concept:stream-extractable "25.6.6.2 Class template basic_­istream_­view [range.istream.view]")<Val, CharT, Traits>class basic_istream_view<Val, CharT, Traits>::*iterator* {public:using iterator_concept = input_iterator_tag; using difference_type = ptrdiff_t; using value_type = Val; constexpr explicit *iterator*(basic_istream_view& parent) noexcept; *iterator*(const *iterator*&) = delete; *iterator*(*iterator*&&) = default; *iterator*& operator=(const *iterator*&) = delete; *iterator*& operator=(*iterator*&&) = default; *iterator*& operator++(); void operator++(int);
Val& operator*() const; friend bool operator==(const *iterator*& x, default_sentinel_t); private: basic_istream_view* *parent_*; // *exposition only*};}
[🔗](#lib:basic_istream_view::iterator,constructor)
`constexpr explicit iterator(basic_istream_view& parent) noexcept;
`
[1](#range.istream.iterator-1)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4120)
*Effects*: Initializes *parent_* with addressof(parent)[.](#range.istream.iterator-1.sentence-1)
[🔗](#lib:operator++,basic_istream_view::iterator)
`iterator& operator++();
`
[2](#range.istream.iterator-2)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4131)
*Effects*: Equivalent to:**parent_*->*stream_* >> *parent_*->*value_*;return *this;
[🔗](#lib:operator++,basic_istream_view::iterator_)
`void operator++(int);
`
[3](#range.istream.iterator-3)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4146)
*Effects*: Equivalent to ++*this[.](#range.istream.iterator-3.sentence-1)
[🔗](#lib:operator*,basic_istream_view::iterator)
`Val& operator*() const;
`
[4](#range.istream.iterator-4)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4157)
*Effects*: Equivalent to: return *parent_*->*value_*;
[🔗](#lib:operator==,basic_istream_view::iterator)
`friend bool operator==(const iterator& x, default_sentinel_t);
`
[5](#range.istream.iterator-5)
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L4168)
*Effects*: Equivalent to: return !*x.*parent_*->*stream_*;
Reference in New Issue View Git Blame Copy Permalink