operator==,!=,<,<=,>,>=,<=>(std::reverse_iterator)

 

C++

编译器支持

独立和宿主式

语言

标准库

标准库头文件

具名要求

Feature test macros (C++20)

语言支持库

Concepts library (C++20)

诊断库

内存管理库

Metaprogramming library (C++11)

通用工具库

容器库

迭代器库

Ranges library (C++20)

算法库

字符串库

文本处理库

数值库

日期和时间库

输入/输出库

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

技术规范

符号索引

外部库

 

迭代器库

迭代器概念
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) is-integer-like is-signed-integer-like (C++20)(C++20)	sentinel_for (C++20) sized_sentinel_for (C++20) input_iterator (C++20) output_iterator (C++20) input_or_output_iterator (C++20)	forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
迭代器原语
input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20)	iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)	iterator (在 C++17 中弃用) iterator_traits incrementable_traits (C++20) indirectly_readable_traits (C++20)
算法概念和工具
间接可调用概念
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)	indirect_unary_predicate (C++20) indirect_binary_predicate (C++20)	indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
常用算法要求
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)
工具
indirect_result_t (C++20)	projected (C++20)	projected_value_t (C++26)
迭代器适配器
reverse_iterator make_reverse_iterator (C++14) move_iterator (C++11) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20)	front_insert_iterator back_insert_iterator inserter insert_iterator front_inserter back_inserter move_sentinel (C++20)	common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) make_const_iterator (C++23) make_const_sentinel (C++23)
流迭代器 istream_iterator    ostream_iterator istreambuf_iterator ostreambuf_iterator	迭代器定制点 ranges::iter_move (C++20) ranges::iter_swap (C++20)
迭代器操作 advance distance prev (C++11)   next (C++11) ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)	范围访问 begincbegin (C++11)(C++14) rbegincrbegin (C++14)(C++14)   endcend (C++11)(C++14) rendcrend (C++14)(C++14)   sizessize (C++17)(C++20) empty (C++17) data (C++17)

 

std::reverse_iterator

成员函数

reverse_iterator::reverse_iterator

reverse_iterator::operator=

reverse_iterator::base

reverse_iterator::operator*reverse_iterator::operator->

reverse_iterator::operator[]

reverse_iterator::operator++reverse_iterator::operator+reverse_iterator::operator+=reverse_iterator::operator--reverse_iterator::operator-reverse_iterator::operator-=

非成员函数

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20)

operator+

operator-

iter_move (C++20)

iter_swap (C++20)

make_reverse_iterator (C++14)

 

定义于头文件 <iterator>
template< class Iter1, class Iter2 > bool operator==( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(1)	(constexpr since C++17)
template< class Iter1, class Iter2 > bool operator!=( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(2)	(constexpr since C++17)
template< class Iter1, class Iter2 > bool operator< ( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(3)	(constexpr since C++17)
template< class Iter1, class Iter2 > bool operator<=( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(4)	(constexpr since C++17)
template< class Iter1, class Iter2 > bool operator> ( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(5)	(constexpr since C++17)
template< class Iter1, class Iter2 > bool operator>=( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(6)	(constexpr since C++17)
template< class Iter1, std::three_way_comparable_with<Iter1> Iter2 > constexpr std::compare_three_way_result_t<Iter1, Iter2>     operator<=>( const std::reverse_iterator<Iter1>& lhs,                  const std::reverse_iterator<Iter2>& rhs );	(7)	(since C++20)

比较 lhs 和 rhs 的底层迭代器。

• 相等性比较的结果被保留（即，相等的底层迭代器意味着相等的逆向迭代器）。
• 关系比较的结果被反转（即，更大的底层迭代器意味着更小的逆向迭代器）。

1) 仅当 lhs.base() == rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。 2) 仅当 lhs.base() != rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。 3) 仅当 lhs.base() > rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。 4) 仅当 lhs.base() >= rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。 5) 仅当 lhs.base() < rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。 6) 仅当 lhs.base() <= rhs.base() 形式良好且可转换为 bool 时，此重载才参与重载解析。

(since C++20)

参数

lhs, rhs

-

要比较的迭代器适配器

返回值

1) lhs.base() == rhs.base()

2) lhs.base() != rhs.base()

3) lhs.base() > rhs.base()

4) lhs.base() >= rhs.base()

5) lhs.base() < rhs.base()

6) lhs.base() <= rhs.base()

7) rhs.base() <=> lhs.base()

注解

operator<=> 返回 rhs.base() <=> lhs.base() 而不是 lhs.base() <=> rhs.base()，因为这是一个逆向迭代器。

示例

运行此代码

#include <cassert>
#include <iterator>
 
int main()
{
    int a[]{0, 1, 2, 3};
    //            ↑  └───── x, y
    //            └──────── z
    // “x” and “y” are equal, but “x” is less than “z” (reversely)
    std::reverse_iterator<int*>
        x{std::rend(a) - std::size(a)},
        y{std::rend(a) - std::size(a)},
        z{std::rbegin(a) + 1};
 
    // two-way comparisons
    assert(  x == y );
    assert(!(x != y));
    assert(!(x <  y));
    assert(  x <= y );
    assert(!(x == z));
    assert(  x != z );
    assert(  x <  z );
    assert(  x <= z );
 
    // three-way comparisons
    assert(  x <=> y == 0 );
    assert(!(x <=> y <  0));
    assert(!(x <=> y >  0));
    assert(!(x <=> z == 0));
    assert(  x <=> z <  0 );
    assert(!(x <=> z >  0));
}

缺陷报告

以下行为变更缺陷报告被追溯应用于先前发布的 C++ 标准。

DR	应用于	已发布行为	正确行为
LWG 280	C++98	不允许异构赋值	允许