drop_view class (C++ Standard Library)

Create a view that excludes the first N elements of a range.

Syntax

template<ranges::view V>
class drop_view : public ranges::view_interface<drop_view<V>>;

Template parameters

V
The type of the underlying view.

View characteristics

For a description of the following entries, see View class characteristics

Characteristic	Description
Range adaptor	views::drop
Underlying range	Must satisfy output_range or higher
Element type	Same as the underlying range
View iterator category	Same as the underlying range
Sized	Only if the underlying range satisfies sized_range
Is const-iterable	Only if the underlying range is const iterable and satisfies random_access_range and sized_range
Common range	Only if the underlying range is a common_range
Borrowed range	Only if the underlying range satisfies borrowed_range

Members

Member functions	Description
ConstructorsC++20	Construct a drop_view.
baseC++20	Get the underlying view.
beginC++20	Get an iterator to the first element.
endC++20	Get the sentinel at the end of the view.
sizeC++20	Get the number of elements in this view. The underlying range must satisfy sized_range.
Inherited from view_interface	Description
backC++20	Get the last element.
dataC++20	Get a pointer to the first element.
emptyC++20	Test whether the drop_view is empty.
frontC++20	Get the first element.
operator[]C++20	Get the element at the specified position.
operator boolC++20	Test whether the drop_view isn't empty.

Requirements

Header: <ranges> (since C++20)

Namespace: std::ranges

Compiler Option: /std:c++20 or later is required.

Constructors

Construct an instance of a drop_view

template<ranges::view V>
class drop_view : public ranges::view_interface<drop_view<V>>

Template parameters

V
The type of the underlying view.

Return value

A view of the underlying range, excluding the specified number of elements from the front.
If you specify more elements to drop than exist in the underlying range, then an empty_view is returned.

Remarks

The best way to create a drop_view is by using the views::drop range adaptor. Range adaptors are the intended way to create view classes. The view types are exposed in case you want to create your own custom view type.

Example: drop_view

// requires /std:c++20 or later
#include <ranges>
#include <iostream>
#include <vector>

int main()
{
    std::vector<int> v{ 1, 2, 3, 4, 5 };
    auto newView = std::views::drop(v, 3);
    for (auto e : newView) // outputs 4 5
    {
        std::cout << e << ' ';
    }
    std::cout << '\n';

    auto numbers = std::views::iota(0) | std::views::take(10); // generate a view of 10 integers
    for (auto i : numbers | std::views::drop(5)) // use the '|' syntax to create a drop_view
    {
        std::cout << i << ' '; // outputs 5 6 7 8 9
    }
}

4 5
5 6 7 8 9

base

Gets a copy of the underlying view.

// Uses a copy constructor to return the underlying view
constexpr V base() const& requires std::copy_constructible<V>;

// Uses a move constructor to return the underlying view
constexpr V base() &&;

Parameters

None.

Return value

The underlying view.

begin

Get an iterator to the first element in the drop_view.

constexpr auto begin()
  requires (!(Simple_view<V> && ranges::random_access_range<const V> && ranges::sized_range<const V>));

constexpr auto begin() const
  requires ranges::random_access_range<const V> && ranges::sized_range<const V>;

Parameters

None.

Return value

An iterator pointing at the first element in the drop_view.

end

Get the sentinel at the end of the drop_view

constexpr auto end() requires (!Simple_view<V>);
constexpr auto end() const requires ranges::range<const V>;

Parameters

None.

Return value

The sentinel that follows the last element in the drop_view:

size

Get the number of elements in the drop_view.

constexpr auto size() requires ranges::sized_range<V>;
constexpr auto size() const requires ranges::sized_range<const V>;

Parameters

None.

Return value

The number of elements in the drop_view.

Remarks

The underlying range must satisfy sized_range.

See also

<ranges>
drop range adaptor
take_while()
take_while_view
View classes