Difference between revisions of "cpp/container/map/empty"
From cppreference.com
m (1 revision: import content) |
m (r2.7.3) (Robot: Adding it:cpp/container/map/empty, ja:cpp/container/map/empty, ru:cpp/container/map/empty) |
||
| Line 1: | Line 1: | ||
{{cpp/container/empty|map}} | {{cpp/container/empty|map}} | ||
| + | |||
| + | [[it:cpp/container/map/empty]] | ||
| + | [[ja:cpp/container/map/empty]] | ||
| + | [[ru:cpp/container/map/empty]] | ||
Revision as of 12:02, 4 May 2012
bool empty() const; |
(noexcept since C++11) | |
Checks if the container has no elements, i.e. whether begin() == end().
Contents |
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::map<int, int> contains any elements:
Run this code
#include <iostream> #include <map> #include <utility> int main() { std::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) |
