NAME¶

std::ranges::views::repeat,std::ranges::repeat_view - std::ranges::views::repeat,std::ranges::repeat_view

Synopsis¶

Defined in header <ranges>
template< std::move_constructible W,

std::semiregular Bound = std::unreachable_sentinel_t >
requires (std::is_object_v<W> && std::same_as<W,
std::remove_cv_t<W>> && (1) (since C++23)
(/*is-integer-like*/<Bound> ||
std::same_as<Bound, std::unreachable_sentinel_t>))

class repeat_view : public ranges::view_interface<repeat_view<W,
Bound>>
namespace views {

inline constexpr /*unspecified*/ repeat = /*unspecified*/; (2) (since C++23)

}
Call signature
template< class W >

requires /* see below */ (since C++23)

constexpr /* see below */ repeat( W&& value );
template< class W, class Bound >

requires /* see below */ (since C++23)

constexpr /* see below */ repeat( W&& value, Bound&& bound );

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 (has the
same effect as) repeat_view(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.

Member functions¶

constructor creates a repeat_view
(public member function)
begin obtains the beginning iterator of a repeat_view
(public member function)
end obtains the sentinel denoting the end of a repeat_view
(public member function)
size obtains the size of a repeat_view if it is sized
(public member function)
Inherited from std::ranges::view_interface
empty returns whether the derived view is empty. Provided if it satisfies
(C++20) sized_range or forward_range.
(public member function of std::ranges::view_interface<D>)
cbegin returns a constant iterator to the beginning of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
cend returns a sentinel for the constant iterator of the range.
(C++23) (public member function of std::ranges::view_interface<D>)
operator bool returns whether the derived view is not empty. Provided if
(C++20) ranges::empty is applicable to it.
(public member function of std::ranges::view_interface<D>)
front returns the first element in the derived view. Provided if it
(C++20) satisfies forward_range.
(public member function of std::ranges::view_interface<D>)
back returns the last element in the derived view. Provided if it satisfies
(C++20) bidirectional_range and common_range.
(public member function of std::ranges::view_interface<D>)
operator[] returns the n^th element in the derived view. Provided if it satisfies
(C++20) random_access_range.
(public member function of std::ranges::view_interface<D>)

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 = (2) (since C++23)
Bound() );
constexpr explicit repeat_view( W&& value, Bound bound = Bound() (3) (since C++23)
);
template < class... WArgs, class... BoundArgs >

requires std::constructible_from<W, WArgs...>
&& std::constructible_from<Bound, BoundArgs...>
constexpr explicit repeat( std::piecewise_construct_t, (4) (since C++23)
std::tuple<WArgs...> value_args,

std::tuple<BoundArgs...> bound_args =
std::tuple<>{} );

1) Value-initializes value_ and bound_ via their default member initializers (= W()
and = Bound()).
2) Initializes value_ with value and initializes bound_ with bound. The behavior is
undefined if Bound is not std::unreachable_sentinel_t and bool(bound >= 0) is false.
3) Initializes value_ with std::move(value) and initializes bound_ with bound. The
behavior is undefined if Bound is not std::unreachable_sentinel_t and bool(bound >=
0) is false.
4) Initializes value_ and bound_ through piecewise construction.

Parameters¶

value - the value to be repeatedly produced
bound - the bound

std::ranges::repeat_view::begin

constexpr /*iterator*/ begin() const; (since C++23)

Returns an iterator initialized with std::addressof(*value_).

std::ranges::repeat_view::end

constexpr /*iterator*/ end() const (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 an iterator initialized with std::addressof(*value_) and bound_.
2) Returns an std::unreachable_sentinel.

std::ranges::repeat_view::size

constexpr auto size() const (since C++23)
requires (!std::same_as<Bound, std::unreachable_sentinel_t>);

Returns the size of the view if the view is bounded. Equivalent to return
/*to-unsigned-like*/(bound_);.

The exposition-only function template to-unsigned-like converts its argument (which
must be integer-like) to the corresponding unsigned version of the argument type.

Deduction guides

template< class W, class Bound > (since C++23)
repeat_view( W, Bound ) -> repeat_view<W, Bound>;

Nested classes

iterator the iterator type
(C++23) (exposition-only member class*)

Notes¶

Feature-test macro Value Std Feature
__cpp_lib_ranges_repeat 202207L (C++23) std::ranges::repeat_view

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 ...

See also¶

ranges::iota_view a view consisting of a sequence generated by repeatedly
views::iota incrementing an initial value
(C++20) (class template) (customization point object)