std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::value_comp - cppreference.com (original) (raw)

| value_compare value_comp() const; | | (since C++23) (constexpr since C++26) | | ----------------------------------- | | ------------------------------------- |

Returns a function object that compares objects of type value_type (key-value pairs) by using key_comp() to compare the first components of the pairs.

[edit] Return value

The value comparison function object.

[edit] Complexity

Constant.

[edit] Example

#include #include #include   // Example module 97 key compare function struct ModCmp { bool operator()(int lhs, int rhs) const { return (lhs % 97) < (rhs % 97); } };   int main() { std::flat_map<int, char, ModCmp> cont; cont = {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}, {5, 'e'}};   auto comp_func = cont.value_comp();   for (const std::pair<int, char> val = {100, 'a'}; auto it : cont) { const bool before = comp_func(it, val); const bool after = comp_func(val, it);   std::cout << '(' << it.first << ',' << it.second << ") "; if (!before && !after) std::cout << "equivalent to key (" << val.first << ")\n"; else if (before) std::cout << "goes before key (" << val.first << ")\n"; else if (after) std::cout << "goes after key (" << val.first << ")\n"; else std::unreachable(); } }

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)

[edit] See also

| | returns the function that compares keys (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |