Cascading of Input/Output Operators in C++ - GeeksforGeeks

28 Dec, 2020
Prerequisite: Operator Overloading in C++, Types of Operator Overloading
When an object calls an operator function by passing an argument and the returned value of the operator function calls the next operator function in the same expression, it is called as cascading of operators. Below are the examples for illustration of Cascading Of Operations:
Program 1:
C++
// C++ program to illustrate the// cascading operators#include <iostream>using namespace std;  // Height Classclass Height {private:    int feet, inches;  public:    // Default Constructor    Height()    {        feet = 0;        inches = 0;    }      // Function to assign value to    // the object of class Height    void setData(int x, int y)    {        feet = x;        inches = y;    }      // Function to print the object    // of the class    void showData()    {        cout << feet << "'" << inches;    }      // Function for overloading    // of operator +    Height operator+(Height H)    {        Height temp;          // Add the feets        temp.feet = feet + H.feet;          // Add the inches        temp.inches = inches + H.inches;        return temp;    }      // Function to normalize the height    // into proper terms of 1 feet    // per 12 inches    void normalize()    {        // Update the feets        if (inches == 12 || inches > 12) {            feet = feet + inches / 12;        }          // Update Inches        inches = inches % 12;    }};  // Driver Codeint main(){    Height h1, h2, h3, h4;      // Initialize the three heights    h1.setData(5, 9);    h2.setData(5, 2);    h3.setData(6, 2);      // Add all the heights using    // cascading of operators    h4 = h1 + h2 + h3;      // Normalize the heights    h4.normalize();      // Print the height h4    h4.showData();      return 0;}
Explanation:In this code, Cascading of the operator is taking place here:
h4 = h1 + h2 + h3;
Here at first h1 object called (+) operator and passes h2 as an argument in the operator function call and the returned value of this operator function calls again (+) operator and passes h3 as an argument in the same expression, at last, the returned value of this second operator function is assigned in h4.
Program 2: The multiple uses of input or output operators (“>>” or ”<<”) in one statement is also an example of cascading of Input/Output operator.
cout is an object of predefined ostream class.
There are several insertions (“<<”) operator functions defined in ostream class for different primitive data types. For Non-primitive data types, you have to define them using the friend function.
Below is the program for overloading of ‘>>’ and ‘<<‘ operators, which takes a number N as an input continuously and insert the number N in the linked list until N = -1.
C++
// C++ program to demonstrate the// overloading of '<<' and '>>'// operators#include <iostream>using namespace std;  // Class for each node object// of the linked listclass node {public:    // Node of the linked list    int data;    node* next;      // Constructor of node class    node(int d)    {        data = d;        next = NULL;    }};  // Insert a node at head of linked// listvoid insertAtHead(node*& head, int d){    node* n = new node(d);    n->next = head;    head = n;}  // Insert a node at tail of linked// listvoid insertAtTail(node* head, int data){    // Make new node using    // constructor    node* n = new node(data);    node* temp = head;      // Traverse till we get to end of    // the linked list    while (temp->next != NULL)        temp = temp->next;      // Append the new node n at the end    // of the linked list    temp->next = n;}  // Print the node at the linked listvoid print(node* head){    // Print the first Node    if (head != NULL) {        cout << head->data;        head = head->next;    }      // Traverse till head traverse    // till end    while (head != NULL) {        cout << "->" << head->data;        head = head->next;    }}  // Function that takes continuous input// until user enter -1 while initializing// the linked list.void takeInput(node*& head){    int n;    cin >> n;      // If n is not equals to -1 insert    // the node in the linked list    while (n != -1) {          // If head is NULL, insert at        // the beginning of list        if (head == NULL)            insertAtHead(head, n);        else            insertAtTail(head, n);        cin >> n;    }}  // Overloading the ostream operator '<<'// to print the complete linked list from// beginningostream& operator<<(ostream& os, node* head){    print(head);}  // Overloading the istream operator '>>'// to take continuous input into the linked// list until user inputs -1istream& operator>>(istream& is, node*& head){    takeInput(head);}  // Driver Codeint main(){    // initialise head to NULL    node* head = NULL;      // Overloading of '>>' for inserting    // element in the linked list    cin >> head;      // Overloading of '<<' for printing    // element in the linked list    cout << head;    return 0;}
Input:
Output:
Some important points about the cascading of operators:
There is no limit on the cascading of operators in a program.
The operator function called must return an object of the same class whose object called this operator function otherwise how will the returned value will call the operator function of the same class.
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