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std::multiset<Key,Compare,Allocator>::key_comp

From cppreference.com
< cpp‎ | container‎ | multiset
 
 
 
 
key_compare key_comp() const;

Returns the function object that compares the keys, which is a copy of this container's constructor argument comp. It is the same as value_comp.

Contents

[edit] Parameters

(none)

[edit] Return value

The key comparison function object.

[edit] Complexity

Constant.

[edit] Example

#include <iostream>
#include <set>
#include <utility>
 
// Example module 97 key compare function
struct ModCmp
{
    bool operator()(int lhs, int rhs) const
    {
        return (lhs % 97) < (rhs % 97);
    }
};
 
int main()
{
    std::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();
    }
}

Output:

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)

[edit] See also

returns the function that compares keys in objects of type value_type
(public member function) [edit]