std::set<Key,Compare,Allocator>::empty (3) - Linux Manuals

std::set<Key,Compare,Allocator>::empty: std::set<Key,Compare,Allocator>::empty

Command to display std::set<Key,Compare,Allocator>::empty manual in Linux: $ man 3 std::set<Key,Compare,Allocator>::empty

NAME

std::set<Key,Compare,Allocator>::empty - std::set<Key,Compare,Allocator>::empty

Synopsis

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:
// Run this code

#include <set>
#include <iostream>

  int main()
  {
      std::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