PHP - Ds Deque::isEmpty() Function

---

---

The PHPDs\Deque::isEmpty()function is used to determine whether the current deque is empty. This function returns a boolean value 'true' if the current deque is empty ([]), otherwise, it returns 'false'.

The Ds\Deque class provides another function called count() that returns the number of elements in the deque. For an empty deque, it returns 0.

Syntax

Following is the syntax of the PHP Ds\Deque::isEmpty() function −

public Ds\Deque::isEmpty(): bool 

Parameters

This function does not accept any parameter.

Return value

This function returns "true" if the deque is empty; otherwise, it returns "false".

Example 1

If the current deque is empty ([]), the Ds\Deque::isEmpty() function will return 'true' as follows −

<?php
   $deque = new \Ds\Deque([]);
   echo "The deque elements are: \n";
   print_r($deque);
   echo "Is the deque empty?: ";
   var_dump($deque->isEmpty());
?>

Output

The above program returns 'true' −

The deque elements are:
Ds\Deque Object
(
)
Is the deque empty?: bool(true)

Example 2

If the current deque is not empty, this function will return 'false'.

Following is another example of the PHP Ds\Deque::isEmpty() function. We use this function to check whether this deque ([10, 20, 30, 40, 50]) is empty −

<?php
   $deque = new \Ds\Deque([10, 20, 30, 40, 50]);
   echo "The deque elements are: \n";
   print_r($deque);
   echo "Is the deque empty?: ";
   var_dump($deque->isEmpty());
?>

Output

After executing the above program, it will return 'false'.

The deque elements are: 
Ds\Deque Object
(
    [0] => 10
    [1] => 20
    [2] => 30
    [3] => 40
    [4] => 50
)
Is the deque empty?: bool(false)

Example 3

Let's use the function result within the conditional statement to check whether the current deque ([1, 2, 3]) is empty or not −

<?php
   $deque = new \Ds\Deque([1, 2, 3]);
   echo "The deque elements are:\n";
   print_r($deque);
   #using isEmpty() function
   $bool = $deque->isEmpty();
   if($bool){
      echo "The deque is empty";
   }
   else{
      echo "The deque is not empty";
   }
?>

Output

On executing the above program, the following output will be displayed −

The deque elements are:
Ds\Deque Object
(
    [0] => 1
    [1] => 2
    [2] => 3
)
The deque is not empty