std::map key_comp() method

od C++98

// Const version onlykey_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 - O(1).

Exceptions

(none)

Example

Main.cpp

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