std::ranges::take_view<V>::size

 

C++

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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::take_view

成員函式

take_view::take_view

take_view::base

take_view::begin

take_view::end

take_view::size

推導指引

哨兵 (Sentinel)

成員函式

take_view::sentinel::sentinel

非成員函式

take_view::sentinel::base

operator==(std::counted_iterator,take_view::sentinel)

 

constexpr auto size() requires ranges::sized_range<V>;	(1)	(C++20 起)
constexpr auto size() const requires ranges::sized_range<const V>;	(2)	(C++20 起)

返回元素數量，其為傳遞給建構函式計數值與底層檢視大小兩者中的較小值。

設 base_ 為底層檢視，count_ 為底層計數器（若預設構造則等於 ​0​）。等價於

auto n = ranges::size(base_);
return ranges::min(n, static_cast<decltype(n)>(count_));

引數

(無)

返回值

元素數量。

示例

執行此程式碼

#include <iostream>
#include <ranges>
 
int main()
{
    constexpr int arr[]{1, 2, 3};
 
    for (int i = 0; i != 6; ++i)
    {
        const auto tv = std::ranges::take_view{arr, i};
        std::cout << tv.size() << ' ';
    }
    std::cout << '\n';
}

輸出

0 1 2 3 3 3

參閱

ranges::size (C++20)	返回等於範圍大小的整數 (定製點物件)
ranges::ssize (C++20)	返回等於範圍大小的有符號整數 (定製點物件)