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std::ranges::drop_view::begin(3) | C++ Standard Libary | std::ranges::drop_view::begin(3) |
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 <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';
}
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)
2022.07.31 | http://cppreference.com |