std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::empty
From cppreference.com
bool empty() const noexcept; |
(since C++23) | |
Checks if the underlying containers have no elements. Equivalent to: return begin() == end();.
Parameters
(none)
Return value
true if the underlying containers are empty, false otherwise.
Complexity
Constant.
Example
The following code uses empty to check if a std::flat_map<int, int> contains any elements:
Run this code
#include <iostream>
#include <flat_map>
#include <utility>
int main()
{
std::flat_map<int,int> numbers;
std::cout << std::boolalpha;
std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
numbers.emplace(42, 13);
numbers.insert(std::make_pair(13317, 123));
std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}
Output:
Initially, numbers.empty(): true
After adding elements, numbers.empty(): false
See also
| returns the number of elements (public member function) | |
(C++17) |
checks whether the container is empty (function template) |