bool empty() const; | (since C++11) |
Checks if the container has no elements, i.e. whether begin() == end().
Parameters
(none).
Return value
true if the container is empty, false otherwise.
Exceptions
noexcept specification: noexceptComplexity
Constant.
Example
The following code uses empty to check if a std::unordered_set<int> contains any elements:
#include <unordered_set>
#include <iostream>
int main()
{
std::unordered_set<int> numbers;
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(): 1 After adding elements, numbers.empty(): 0
See also
| returns the number of elements (public member function) |
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