std::ranges::elements_view<V,F>::iterator<Const>::operator[]

 

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特性測試宏 (C++20)

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技術規範

符號索引

外部庫

 

範圍庫 (Ranges library)

範圍訪問 begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

範圍轉換 (Range conversions) std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

懸空迭代器處理 (Dangling iterator handling) dangling borrowed_iterator_t borrowed_subrange_t

範圍原語 (Range primitives)
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

範圍概念 (Range concepts)
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

檢視
view_interface	subrange

範圍工廠 (Range factories)
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

範圍介面卡 (Range adaptors)
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted to_input_viewviews::to_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

範圍生成器 (Range generators) std::generator (C++23)

範圍介面卡閉包物件 (Range adaptor closure objects) range_adaptor_closure (C++23)

範圍介面卡物件 (Range adaptor objects)

輔助項 (Helper items)
copyable-box movable-box (直到 C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::elements_view

成員函式

elements_view::elements_view

elements_view::base

elements_view::begin

elements_view::end

elements_view::size

巢狀類

迭代器 (Iterator)

elements_view::iterator::iterator

elements_view::iterator::base

elements_view::iterator::operator*

elements_view::iterator::operator[]

elements_view::iterator::operator++ elements_view::iterator::operator++(int) elements_view::iterator::operator-- elements_view::iterator::operator--(int) elements_view::iterator::operator+= elements_view::iterator::operator-=

operator==(elements_view::iterator) operator<(elements_view::iterator) operator>(elements_view::iterator) operator<=(elements_view::iterator) operator>=(elements_view::iterator) operator<=>(elements_view::iterator)

operator+(elements_view::iterator) operator-(elements_view::iterator)

哨兵 (Sentinel)

elements_view::sentinel::sentinel

elements_view::sentinel::base

operator==(elements_view::iterator,elements_view::sentinel)

operator-(elements_view::iterator,elements_view::sentinel)

 

constexpr decltype(auto) operator[]( difference_type n ) const     requires ranges::random_access_range<Base>;		(C++20 起)

返回位於指定相對位置的元素，如同透過 /*get-element*/(this->base() + n)，其中對於表示式 e，/*get-element*/(e) 是

• std::get<N>(*e)，如果 ranges::range_reference_t<Base> 是引用型別。否則是
• static_cast<E>(std::get<N>(*e))，其中 E 是 std::remove_cv_t<std::tuple_element_t<N, ranges::range_reference_t<Base>>>。

引數

n

-

相對於當前位置的偏移量

返回值

相對於當前位置，在位移 n 處的元素。

示例

執行此程式碼

#include <iostream>
#include <ranges>
#include <string_view>
#include <tuple>
 
int main()
{
    using T = std::tuple<int, char, std::string_view>;
 
    const auto il =
    {
        T{1, 'A', "α"},
        T{2, 'B', "β"},
        T{3, 'C', "γ"},
    };
 
    std::cout << std::views::elements<0>(il)[1] << ' '   // 2
              << std::views::elements<1>(il)[1] << ' '   // B
              << std::views::elements<2>(il)[1] << '\n'; // β
}

輸出

2 B β

參閱

operator* (C++20)

訪問第 N 個元組元素 (公開成員函式)