C++ Deque Operator Function

In C++, the Standard Template Library (STL) provides a diverse selection of container classes, with the deque (double-ended queue) standing out as a particularly versatile option. Apart from its adaptability, the deque demonstrates efficient performance when adding or removing elements at either end. This efficiency makes the deque a compelling choice over the vector in certain scenarios.

In C++, the Deque operator= method plays a crucial role within the deque container. This function facilitates the transfer of content from one deque to another. By executing this function, a new set of elements is assigned to the container, thereby replacing the existing elements of the same type. Consequently, the size of the deque can be adjusted as needed. This functionality is significant for maintaining container assignment semantics, ensuring efficient move semantics for deque objects through deep copying.

Syntax:

It has the following syntax.

deque& operator=(const deque& other);          // Copy assignment

deque& operator=(deque&& other) noexcept;      // Move assignment (C++11)

deque& operator=(initializer_list<T> ilist);   // Initializer list assignment (C++11)

In this instance,

• ✅ alternative: It represents a deque container that requires duplication into a separate deque entity.
• ✅ ilist: This parameter is employed for specifying an initializer list comprising elements designated for assignment within the deque.

Return value:

It provides a reference to the current deque object *this.

Types of Assignment with deque::operator=

There are mainly three important types of the deque assignment operator. Some of them are as follows:

• ✅ Copy Assignment
• ✅ Move Assignment
• ✅ Initializer List Assignment

Here, we will address each of these tasks individually.

Copy Assignment

In C++, copy assignment is frequently employed to duplicate the elements of one deque into another deque. The size and elements of the target deque are overwritten. Modifying one deque does not impact the other deque.

Simple C++ Deque Operator = Example

Let's consider an instance to demonstrate the basic deque operator = in C++.

Example

#include <iostream>  

#include<deque>  

using namespace std;    //using standard namespace

int main()  //main function

{  

  deque<int> a={1,2,3,4,5};  

  deque<int> b;  

  b.operator=(a);  

  for(int i=0;i<b.size();i++)  

  {  

      cout<<b[i];  

      cout<<" ";  

  }  

   return 0;  

}

Output:

1 2 3 4 5

Explanation:

In this instance, we have established two deque containers, 'a' and 'b'. 'a' contains the elements {1, 2, 3, 4, 5}, while 'b' is currently empty. Subsequently, the b.operator=(a) method is employed to duplicate all elements from deque 'a' to deque 'b'. This method effectively substitutes all of 'b's content with that of 'a'. Lastly, a for loop is utilized to traverse through deque 'b' and exhibit each element, showcasing the duplicated elements.

Move Assignment

Transfer assignment in C++ is employed to shift resources from one deque to another without executing a deep copy. The initial deque will undergo the transfer and end up empty (although still usable). This method is generally more effective for temporary entities.

C++ Move Assignment Operator with deque operator= Example

Let's consider an instance to demonstrate the move assignment operator using the deque operator = in C++.

Example

#include <iostream>

#include <deque>

using namespace std;  //using standard namespace

int main() {   //main function

    deque<string> a = {"C++", "Move Assignment Operator Deque", "Example"};

    deque<string> b;

    b = move(a);   // Move assignment

    cout << "Deque a after move assignment: ";

    for (auto &str : b)

        cout << str << " ";

    cout << "\nDeque a size after move: " << a.size();

    return 0;

}

Output:

Deque a after move assignment: C++ Move Assignment Operator Deque Example 

Deque a size after move: 0

Explanation:

In this instance, a deque named a is instantiated with string items, while deque b remains empty. Subsequently, the b = move(a) method is employed to shift the elements from a to b without duplication. Following the move process, all data originally in deque a is seamlessly transferred to deque b, resulting in deque a being emptied. Lastly, the contents of deque b are showcased, illustrating that deque a has a size of 0 post move assignment.

Initializer List Assignment

In C++, an initializer list assignment is frequently employed to assign values directly from brace-enclosed lists using an initializer list ({}). This method is a convenient approach to assign predetermined values all at once.

C++ Initializer List Assignment using deque operator = Example

Let's consider an example to demonstrate the assignment of initializer list using the deque operator = Function in the C++ programming language.

Example

#include <iostream>

#include <deque>

using namespace std;  //using standard namespace

int main() {   //main function

    deque<int> a = {1, 2, 3};

    a = {15, 20, 25, 30, 45};  // Initializer list assignment

    cout <<"The deque after initializer list assignment: ";

    for (int num : a)

        cout << num << " ";

    return 0;

}

Output:

The deque after initializer list assignment: 15 20 25 30 45

Explanation:

In this instance, a deque named a is established with the initial elements {1, 2, 3}. Subsequently, we employ a={15, 20, 25, 30, 35} to substitute the existing elements with a fresh set of values. This action eliminates the prior elements and allocates the new values from the list of initializers to the deque. Ultimately, the revised deque is presented, showcasing 15 20 25 30 35 as the resulting output.

Features of the Deque operator = in C++

There are several features of the Deque operator = in C++. Some of them are as follows:

• ✅ In C++, it allows us to replace the content of one deque with another deque.
• ✅ This operator allows us to assign the values in various ways, such as: Copy Assignment, Move Assignment, and Initializer List assignment.
• ✅ It returns a reference to the current deque (*this), which enables chained assignments like a = b = c;.
• ✅ It provides better exception handling, which ensures that no data is missing if an exception occurs.
• ✅ When we use the deque operator=, the available elements are automatically destroyed from the deque, and new elements are included as required.

Conclusion

In summary, the deque::operator= method in C++ serves as an intrinsic member function within the double-ended queues container. Its purpose includes duplicating data from an existing deque, transferring values without the overhead of duplication, and promptly resetting values via an initializer list. This function facilitates various approaches to initializing a value within the deque, such as copy assignment, move assignment, and assignment through an initializer list.

C++ Deque Operator = Function FAQs

Assigning a deque to itself in C++, such as dq = dq;, will not result in any changes to the deque.

In the C++ coding language, self-assigning the deque (dq = dq;) is securely managed. This feature carefully examines and handles various scenarios to avoid any risk of data corruption. The data within the deque will stay unaltered, making this action equivalent to a no-operation.

The primary objective of the deque operator = function in C++ is to assign the elements of one deque container to another deque container.

In C++, the deque operator= method is frequently employed to assign fresh data to a deque and substitute the existing elements within the deque. This function enables us to transfer the content of one deque to another. It assigns updated data to the container, effectively replacing the current content of a similar type. Consequently, the size of the deque can be adjusted as needed.

The time complexity of the assignment operator in C++ is typically O(1).

The time complexity of the assignment operator differs in all ways.

• ✅ Copy Assignment: It has a time complexity of O(n).
• ✅ Move Assignment: It has a time complexity of O(1), which means constant time complexity.
• ✅ Initializer List Assignment: It has a time complexity of O(n).

The disparity between the operator= function and the deque::assign function in C++ lies in how they are used to assign values to deque containers. The operator= function is employed to assign values from one deque to another, while the deque::assign function is utilized to assign new values to a deque by replacing its current contents.

The primary contrast between the operator = function and the assign operator lies in their functionalities. While the operator = function is employed to substitute all the contents within the deque, the deque::assign function offers a broader range of options for assignment. These include specifying a certain quantity of elements, defining a range, and various other possibilities.

In C++, the operator = function supports various types of assignments.

There are mainly three types of assignment used with the operator = function in C++.

• ✅ Copy Assignment
• ✅ Move Assignment
• ✅ Initializer List Assignment