| (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: noexcept
Complexity
Constant.
Example
The following code uses empty
to check if a std::unordered_map<int,int>
contains any elements:
1 2 3 4 5 6 7 8 9 10 11 12 13 | #include <unordered_map> #include <iostream> #include <utility> int main() { std::unordered_map< int , int > numbers; 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:
1 2 | Initially, numbers.empty(): 1 After adding elements, numbers.empty(): 0 |
See also
returns the number of elements (public member function) |
Please login to continue.