iter_swap(std::common_iterator)

 

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indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20)	indirectly_copyable_storable (C++20)   indirectly_swappable (C++20) indirectly_comparable (C++20)	permutable (C++20) mergeable (C++20) sortable (C++20)
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流迭代器 istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	迭代器定製點 ranges::iter_move (C++20) ranges::iter_swap (C++20)
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std::common_iterator

成員函式

common_iterator::common_iterator

common_iterator::operator=

common_iterator::operator*common_iterator::operator->

common_iterator::operator++common_iterator::operator++(int)

非成員函式

operator== (C++20)

operator- (C++20)

iter_move (C++20)

iter_swap (C++20)

輔助類

incrementable_traits<std::common_iterator> (C++20)

iterator_traits<std::common_iterator> (C++20)

 

template< std::indirectly_swappable<I> I2, class S2 > friend constexpr void     iter_swap( const common_iterator& x,                const std::common_iterator<I2, S2>& y ) noexcept(/*見下文*/);		(C++20 起)

交換兩個底層迭代器所指向的物件。如果 x 不持有 I 物件或 y 不持有 I2 物件（即 x 和 y 至少有一個不持有迭代器），則行為未定義。

函式體等價於 ranges::iter_swap(std::get<I>(x.var), std::get<I2>(y.var))。

此函式模板對常規非限定或限定查詢不可見，只能通過當 std::common_iterator<I,S> 是引數的關聯類時，實參依賴查詢才能找到。

引數

x, y

-

要交換元素的迭代器

返回值

(無)

複雜度

常數時間。

異常

noexcept 規範：  

noexcept(noexcept(ranges::iter_swap(std::declval<const I&>(), std::declval<const I2&>())))

示例

執行此程式碼

#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
 
int main()
{
    std::vector<std::string> v1{"1", "2", "3", "4", "5"},
                             v2{"α", "β", "γ", "δ", "ε"};
 
    using CI = std::common_iterator<
                   std::counted_iterator<std::vector<std::string>::iterator>,
                   std::default_sentinel_t
                   >;
 
    CI first1{std::counted_iterator{v1.begin(), 3}};
    CI first2{std::counted_iterator{v2.begin(), 4}};
    CI last{std::default_sentinel};
 
    auto print = [&](auto rem)
    {
        std::cout << rem << "v1 = ";
        std::ranges::copy(v1, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << "\nv2 = ";
        std::ranges::copy(v2, std::ostream_iterator<std::string>{std::cout, " "});
        std::cout << '\n';
    };
 
    print("Before iter_swap:\n");
 
    for (; first1 != last && first2 != last; ++first1, ++first2)
        iter_swap(first1, first2); // ADL
 
    print("After iter_swap:\n");
}

輸出

Before iter_swap:
v1 = 1 2 3 4 5 
v2 = α β γ δ ε 
After iter_swap:
v1 = α β γ 4 5 
v2 = 1 2 3 δ ε

缺陷報告

下列更改行為的缺陷報告追溯地應用於以前出版的 C++ 標準。

缺陷報告	應用於	釋出時的行為	正確的行為
LWG 3574	C++20	variant 完全為 constexpr (P2231R1) 但 common_iterator 不是	也設為 constexpr

亦可見

swap	交換兩個物件的值 (函式模板)
swap_ranges	交換兩個範圍的元素 (函式模板)
iter_swap	交換兩個迭代器所指向的元素 (函式模板)
iter_swap (C++20)	交換兩個可解引用物件所引用的值 (定製點物件)
iter_swap (C++20)	交換兩個底層迭代器指向的物件 (函式模板)