NAME¶

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

Synopsis¶

constexpr auto begin()

requires (!(__SimpleView<V> && (1) (since C++20)
ranges::random_access_range<const V> &&

ranges::sized_range<const V>));
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.

Parameters¶

(none)

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.

Example¶

// Run this code

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

void println(std::ranges::range auto const& range)
{
for (auto const& elem : range)
std::cout << elem;
std::cout << '\n';
}

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

const auto pos = std::distance(hi.begin(), std::ranges::find(hi, 'C'));
auto cxx = std::ranges::drop_view{hi, pos};
std::cout << "*drop_view::begin() == '" << *cxx.begin() << "'\n";
// *cxx.begin() = 'c'; // undefined: 'views' are to be used as observers
println(cxx);
}

Output:¶

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

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)