std::ranges::drop_view<V>::size

 

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begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
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iterator_tsentinel_t	range_size_trange_difference_t	range_reference_trange_rvalue_reference_t	range_value_t
悬垂迭代器处理
dangling	borrowed_iterator_t	borrowed_subrange_t
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range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
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view_interface	subrange
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empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	basic_istream_viewviews::istream
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views::all_tviews::all ref_view owning_view common_viewviews::common reverse_viewviews::reverse views::counted zip_viewviews::zip (C++23)(C++23)	take_viewviews::take take_while_viewviews::take_while drop_viewviews::drop drop_while_viewviews::drop_while zip_transform_viewviews::zip_transform (C++23)(C++23)	elements_viewviews::elements keys_viewviews::keys values_viewviews::values transform_viewviews::transform adjacent_viewviews::adjacent (C++23)(C++23)	filter_viewviews::filter join_viewviews::join split_viewviews::split lazy_split_viewviews::lazy_split adjacent_transform_viewviews::adjacent_transform (C++23)(C++23)
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辅助项
copyable-box	simple-view

 

std::ranges::drop_view

成员函数

drop_view::drop_view (C++20)

drop_view::base (C++20)

drop_view::begin (C++20)

drop_view::end (C++20)

drop_view::size (C++20)

推导指引 (C++20)

 

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)

返回元素数。

令 base_ 为底层视图， count_ 为存储的计数（通常为传递给构造函数的数，或若 *this 为默认构造则为 ​0​ ）。等价于

const auto s = ranges::size(base_);
const auto c = static_cast<decltype(s)>(count_);
return s < c ? 0 : s - c;

参数

（无）

返回值

元素数。

示例

运行此代码

#include <array>
#include <ranges>
 
int main()
{
    constexpr std::array a{42, 43, 44};
    static_assert(std::ranges::drop_view{std::views::all(a), 0}.size() == 3);
    static_assert(std::ranges::drop_view{std::views::all(a), 1}.size() == 2);
    static_assert(std::ranges::drop_view{std::views::all(a), 2}.size() == 1);
    static_assert(std::ranges::drop_view{std::views::all(a), 3}.size() == 0);
    static_assert(std::ranges::drop_view{std::views::all(a), 4}.size() == 0);
}

参阅

ranges::size (C++20)	返回等于范围大小的整数 (定制点对象)
ranges::ssize (C++20)	返回等于范围大小的有符号整数 (定制点对象)