C++ Array::empty() Function

The C++ std::array::empty() function is used to check whether a array is empty. Since the std::array is a fixed size container, its size is known at compile time, and it cannot be dynamically resized. This function always return false for std::array because array is never empty unless it has zero size(which is rare).

Syntax

Following is the syntax for std::array::empty() function.

constexpr bool empty() noexcept;

Parameters

This does not accepts any parameter.

Return Value

It returns a bool value indicating whether the array is empty or not.

Exceptions

This function never throws exception.

Time complexity

Constant i.e. O(1)

Example 1

In the following example, we are going to consider the basic usage of the empty() function.

#include <iostream>
#include <array>
using namespace std;
int main() {
   array < int, 10 > myarray {9,12,15,18,21,24,27,30,33,36};
   if (myarray.empty()) {
      cout << "True";
   } else {
      cout << "False";
   }
   return 0;
}

Output

Output of the above code is as follows −

False

Example 2

Consider the following example, where we are going to consider two array one with size zero and another with size 10.

#include <iostream>
#include <array>
using namespace std;
int main(void) {
   array < int, 0 > arr1;
   array < int, 10 > arr2;
   if (arr1.empty())
      cout << "arr1 is empty" << endl;
   else
      cout << "arr1 is not empty" << endl;
   if (arr2.empty())
      cout << "arr2 is empty" << endl;
   else
      cout << "arr2 is not empty" << endl;
}

Output

Following is the output of the above code −

arr1 is empty
arr2 is not empty