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std::ranges::drop_view::begin(3) C++ Standard Libary std::ranges::drop_view::begin(3)


std::ranges::drop_view::begin - std::ranges::drop_view::begin


constexpr auto begin()

requires (!(__SimpleView<V> && (1) (since C++20)

ranges::random_access_range<const V> && ranges::sized_range<const
constexpr auto begin() const
requires ranges::random_access_range<const V> && (2) (since C++20)
ranges::sized_range<const V>;

Returns an iterator to the first element of the drop_view, that is, an iterator to
the N-th element of the underlying view, or to the end of the underlying view if it
has less than N elements.

If V is not a random_access_range or a sized_range, in order to provide the
amortized constant time complexity required by the range concept, the overload (1)
caches the result within the drop_view object for use on subsequent calls.



Return value

ranges::next(ranges::begin(base_), count_, ranges::end(base_)), where base_ is the
underlying view, and count_ is the number of elements to skip.


// Run this code

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <ranges>

int main()
std::array hi{ 'H','e','l','l','o',',',' ','C','+','+','2','0','!' };

std::ranges::for_each(hi, [](const char c){ std::cout << c; });
std::cout << '\n';

const auto c = std::distance(hi.begin(), std::ranges::find(hi, 'C'));
auto cxx = std::ranges::drop_view{ hi, c };
std::cout << "*drop_view::begin() == '" << *cxx.begin() << "'\n";

// *cxx.begin() = 'c'; // undefined: 'views' are to be used as observers

for (char c : cxx) { std::cout << c; }
std::cout << '\n';


Hello, C++20!
*drop_view::begin() == 'C'

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 3482 C++20 the const overload can be called the const overload requires
with unsized ranges sized_range

See also

end returns an iterator or a sentinel to the end
(C++20) (public member function)
ranges::begin returns an iterator to the beginning of a range
(C++20) (customization point object)
ranges::end returns a sentinel indicating the end of a range
(C++20) (customization point object)