std::ranges::views::take, std::ranges::take_view

template< ranges::view V > class take_view : public ranges::view_interface<take_view<V>>	(1)	(since C++20)
namespace views { inline constexpr /unspecified/ take = /unspecified/; }	(2)	(since C++20)

1) A range adaptor that represents view of the first N elements from an underlying sequence, or all elements if the underlying sequence contains fewer than N.

2) The expression views::take(E, F) results in a view that represents the first F elements from E. The result is not necessarily a take_view.

It is expression-equivalent to (where T is std::remove_cvref_t<decltype((E))> and D is ranges::range_difference_t<decltype((E))>):

((void)F, static_cast<T>(E)), if T is a ranges::empty_view;
T{ranges::begin(E), ranges::begin(E) + std::min<D>(ranges::size(E), F)}, if T models both random_access_range and sized_range, and T is a specialization of

std::span where T::extent == std::dynamic_extent,
std::basic_string_view,
ranges::iota_view, or
ranges::subrange;

otherwise, take_view{E, F}.

In all cases, decltype((F)) must model std::convertible_to<D>.

take_view models the concepts contiguous_range, random_access_range, bidirectional_range, forward_range, input_range, and sized_range when the underlying view V models respective concepts. It models common_range when the underlying view V models both random_access_range and sized_range.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

Member functions

(constructor)	constructs a `take_view` (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements. Provided only if the underlying (adapted) range satisfies `sized_range` (public member function)

Deduction guides

Nested classes

sentinel

the sentinel type
(public member class)

Example

Run this code

#include <ranges>
#include <algorithm> // for std::ranges::for_each
#include <iostream>
 
auto print = [](char x) { std::cout << x; };
 
int main()
{
    constexpr char pi[] { '3', '.', '1', '4', '1', '5', '9', '2', '6', '5' };
 
    std::ranges::for_each(pi | std::ranges::views::take(8), print);
    std::cout << '\n';
 
    std::ranges::for_each(std::ranges::take_view{pi, 8}, print);
    std::cout << '\n';
}

Output:

3.141592
3.141592

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications