std::set<Key,Compare,Allocator>::empty
bool empty() const; |
(until C++11) | |
bool empty() const noexcept; |
(since C++11) (until C++20) |
|
[[nodiscard]] bool empty() const noexcept; |
(since C++20) |
Checks if the container has no elements, i.e. whether begin() == end()
.
Parameters
(none).
Return value
true
if the container is empty, false
otherwise.
Complexity
Constant.
Example
The following code uses empty
to check if a std::set<int>
contains any elements:
#include <set> #include <iostream> int main() { std::set<int> numbers; std::cout << std::boolalpha; std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n'; numbers.insert(42); numbers.insert(13317); 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) |
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