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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Tables

Iterator invalidation

Member function table

Non-member function table

 

std::flat_multiset

Member types

Member functions

flat_multiset::flat_multiset   flat_multiset::operator= Iterators flat_multiset::beginflat_multiset::cbegin flat_multiset::endflat_multiset::cend flat_multiset::rbeginflat_multiset::crbegin flat_multiset::rendflat_multiset::crend Capacity flat_multiset::size flat_multiset::max_size flat_multiset::empty Observers flat_multiset::key_comp flat_multiset::value_comp Modifiers flat_multiset::clear flat_multiset::insert flat_multiset::insert_range flat_multiset::emplace flat_multiset::emplace_hint flat_multiset::erase flat_multiset::swap flat_multiset::extract flat_multiset::replace Lookup flat_multiset::count flat_multiset::find flat_multiset::contains flat_multiset::equal_range flat_multiset::lower_bound flat_multiset::upper_bound

Non-member functions

swap(std::flat_multiset) erase_if(std::flat_multiset)    operator==operator<=>

Helper classes

uses_allocator<std::flat_multiset>

Tags

sorted_equivalent         sorted_equivalent_t

Deduction guides

 

key_compare key_comp() const;		(since C++23)

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.

Parameters

(none)

Return value

The key comparison function object.

Complexity

Constant.

Example

Run this code

#include <iostream>
#include <flat_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::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();
    }
}

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)

See also

value_comp

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