NAME¶

std::multimap::key_comp - std::multimap::key_comp

Synopsis¶

key_compare key_comp() const;

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

Parameters¶

(none)

Return value¶

The key comparison function object.

Complexity¶

Constant.

Example¶

// Run this code

#include <cassert>
#include <iostream>
#include <map>

// Example module 97 key compare function
struct ModCmp {
bool operator()(const int lhs, const int rhs) const
{
return (lhs % 97) < (rhs % 97);
}
};

int main()
{
std::multimap<int, char, ModCmp> cont;
cont = { { 1, 'a' }, { 2, 'b' }, { 3, 'c' }, { 4, 'd' }, { 5, 'e' } };

auto comp_func = cont.key_comp();

for (auto it : cont) {
bool before = comp_func(it.first, 100);
bool after = comp_func(100, it.first);

std::cout << '(' << it.first << ',' << it.second;
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
assert(0); // Cannot happen
}
}

Output:¶

(1,a) goes before key 100
(2,b) goes before key 100
(3,c) equivalent to key 100
(4,d) goes after key 100
(5,e) goes after key 100

See also¶

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