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std::flat_multiset<Key,Compare,KeyContainer>:: key_comp

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std::flat_multiset
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key_compare key_comp ( ) const ;
(C++23 起)
(C++26 起为 constexpr)

返回用于比较键的函数对象，该对象是 * this 所使用的键比较对象的副本。其功能与 value_comp() 相同。

目录

返回值

关键比较函数对象。

复杂度

常量。

示例

运行此代码 
#include <iostream>
#include <flat_set>
#include <utility>
// 示例模块97键比较函数
struct ModCmp
{
    bool operator()(int lhs, int rhs) const
    {
        return (lhs % 97) < (rhs % 97);
    }
};
int main()
{
    std::flat_multiset<int, ModCmp> cont{1, 2, 3, 4, 5};
    auto comp_func = cont.key_comp();
    for (const int key : cont)
    {
        const bool before = comp_func(key, 100);
        const bool after = comp_func(100, key);
        std::cout << '(' << key << ") ";
        if (!before && !after)
            std::cout << "equivalent to key (100)\n";
        else if (before)
            std::cout << "goes before key (100)\n";
        else if (after)
            std::cout << "goes after key (100)\n";
        else
            std::unreachable();
    }
}

输出： 

Key (1) goes before key (100)
Key (2) goes before key (100)
Key (3) equivalent to key (100)
Key (4) goes after key (100)
Key (5) goes after key (100)

参见

返回用于比较 value_type 类型对象中键的函数
(公开成员函数)