std::ranges::views::repeat, std::ranges::repeat_view
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Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Ranges library
(exposition-only member object*)
returns a constant iterator to the beginning of the range
(public member function of
returns a sentinel for the constant iterator of the range
(public member function of
(C++23)(C++23)
repeat_viewviews::repeat
(C++23)(C++23)
(C++23)(C++23)
(C++26)(C++26)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
std::ranges::repeat_view
Defined in header
<ranges>
template< std::move_constructible W,
(1)
(since C++23)
std::semiregular Bound = std::unreachable_sentinel_t >
requires (std::is_object_v <W> && std::same_as <W, std::remove_cv_t <W>> &&
(/*integer-like-with-usable-difference-type*/<Bound> ||
std::same_as <Bound, std::unreachable_sentinel_t >))
namespace views {
(2)
(since C++23)
inline constexpr /* unspecified */ repeat = /* unspecified */;
Call signature
template< class W >
(since C++23)
requires /* see below */
template< class W, class Bound >
(since C++23)
requires /* see below */
Helper concepts
concept /*integer-like-with-usable-difference-type*/ =
(3)
(exposition only*)
/*is-signed-integer-like*/<T> ||
1) A range factory that generates a sequence of elements by repeatedly producing the same value. Can be either bounded or unbounded (infinite).
2) views::repeat(e) and views::repeat(e, f) are expression-equivalent to repeat_view<std::decay_t <decltype((E))>>(e) and repeat_view(e, f) respectively for any suitable subexpressions e and f.
repeat_view models random_access_range. If Bound is not std::unreachable_sentinel_t , repeat_view also models sized_range and common_range.
Contents
Customization point objects
The name views::repeat denotes a customization point object, which is a const function object of a literal semiregular class type. See CustomizationPointObject for details.
[edit] Data members
Member
Definition
Bound bound_
the sentinel value(exposition-only member object*)
[edit] Member functions
Inherited from std::ranges::view_interface
returns whether the derived view is empty, provided only if it satisfies
(public member function of
sized_range or forward_range (public member function of
std::ranges::view_interface<D>) [edit]
(C++23)
(public member function of
std::ranges::view_interface<D>) [edit]
(C++23)
(public member function of
std::ranges::view_interface<D>) [edit]
returns whether the derived view is not empty, provided only if ranges::empty is applicable to it
(public member function of
(public member function of
std::ranges::view_interface<D>) [edit]
returns the first element in the derived view, provided if it satisfies
(public member function of
forward_range (public member function of
std::ranges::view_interface<D>) [edit]
returns the last element in the derived view, provided only if it satisfies
(public member function of
bidirectional_range and common_range (public member function of
std::ranges::view_interface<D>) [edit]
returns the
(public member function of
nth element in the derived view, provided only if it satisfies random_access_range (public member function of
std::ranges::view_interface<D>) [edit]
std::ranges::repeat_view::repeat_view
repeat_view() requires std::default_initializable <W> = default;
(1)
(since C++23)
constexpr explicit repeat_view( const W& value, Bound bound = Bound() );
(2)
(since C++23)
constexpr explicit repeat_view( W&& value, Bound bound = Bound() );
(3)
(since C++23)
template < class... WArgs, class... BoundArgs >
(4)
(since C++23)
requires std::constructible_from <W, WArgs...>
&& std::constructible_from <Bound, BoundArgs...>
constexpr explicit
repeat( std::piecewise_construct_t, std::tuple <WArgs...> value_args,
If
Bound is not std::unreachable_sentinel_t and bool(bound >= 0) is false, the behavior is undefined. If
Bound is not std::unreachable_sentinel_t and bool(bound >= 0) is false, the behavior is undefined.4) Initializes
value_ with std::make_from_tuple <T>(std::move(value_args)) and bound_ with std::make_from_tuple <Bound>(std::move(bound_args)). If
Bound is not std::unreachable_sentinel_t and bool(bound >= 0) is false, the behavior is undefined.Parameters
value
-
the value to be repeatedly produced
bound
-
the bound
value_args
-
the tuple containing the initializers of
value_
bound_args
-
the tuple containing the initializers of
bound_
std::ranges::repeat_view::begin
constexpr /*iterator*/ begin() const;
(since C++23)
Returns iterator (std::addressof (*value_ )).
std::ranges::repeat_view::end
constexpr /*iterator*/ end() const
requires (!std::same_as <Bound, std::unreachable_sentinel_t >);
(1)
(since C++23)
requires (!std::same_as <Bound, std::unreachable_sentinel_t >);
constexpr std::unreachable_sentinel_t end() const;
(2)
(since C++23)
1) Returns
iterator (std::addressof (*value_ ), bound_ ).2) Returns std::unreachable_sentinel .
std::ranges::repeat_view::size
constexpr auto size() const
requires (!std::same_as <Bound, std::unreachable_sentinel_t >);
(since C++23)
requires (!std::same_as <Bound, std::unreachable_sentinel_t >);
Returns to-unsigned-like (bound_ ).
[edit] Deduction guides
template< class W, class Bound = std::unreachable_sentinel_t >
repeat_view( W, Bound = Bound() ) -> repeat_view<W, Bound>;
(since C++23)
repeat_view( W, Bound = Bound() ) -> repeat_view<W, Bound>;
[edit] Nested classes
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_ranges_repeat |
202207L |
(C++23) | std::ranges::repeat_view
|
[edit] Example
Run this code
#include <iostream> #include <ranges> #include <string_view> using namespace std::literals; int main() { // bounded overload for (auto s : std::views::repeat("C++"sv, 3)) std::cout << s << ' '; std::cout << '\n'; // unbounded overload for (auto s : std::views::repeat("I know that you know that"sv) | std::views::take (3)) std::cout << s << ' '; std::cout << "...\n"; }
Output:
C++ C++ C++ I know that you know that I know that you know that I know that you know that ...
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 4053 | C++20 | unary calls to views::repeat did not decay the argument
|
decay the argument |
| LWG 4054 | C++20 | calling views::repeat with a repeat_viewdid not create a nested repeat_view
|
creates a nestedrepeat_view
|