std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::empty
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std::flat_map
flat_map::empty
bool empty() const noexcept;
(since C++23)
Checks if the underlying containers have no elements. Equivalent to: return begin() == end();.
[edit] Parameters
(none)
[edit] Return value
true if the underlying containers are empty, false otherwise.
[edit] Complexity
Constant.
[edit] 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