Are virtual functions the only way to achieve Runtime Polymorphism in C

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"How is Runtime Polymorphism achieved in C++?" one of my friends inquired. 

"By Inheritance," I replied.

"No, it can only be done with virtual functions," he said.

As a result, I gave him the following code as an example:-

#include<iostream>
using namespace std;

class A
{
public:
    int i;
    A(){i=100;}
};

class B : public A
{
public:
    int j;
    B(){i = -1; j = 99;}
};

void func(A& myA)
{
    cout<<myA.i << endl;
}

int main()
{
    B b;
    A* a = new B();
    func(*a);
    func(b);
    delete a;
    return 0;
}

We can print the value of public member I using the function func(), which takes a reference to A but accepts an object from B. 

Compile time polymorphism, he explained.

My inquiries are as follows:

1) Is virtual function polymorphism the only way to achieve runtime polymorphism?

2) Is the above example polymorphic at runtime or at compile time?

3) In the event that I have the following code:

void func2(A& myA)
{
    cout << myA.i << endl;
    // dynamic/static cast myA to myB
    cout<<myB.j << endl;
}

Is it a polymorphism of some sort? 

Is it polymorphism, or something else?

Jun 6 in C++ by Nicholas
• 2,460 points
16 views

1 answer to this question.

0 votes

fprintf is a polymorphism function in the C programming language.

It can print to a file, stdout, a printer, a socket, or whatever else the system can represent as a stream if you supply it different handles.

FILE* file = fopen("output.txt", "w");                    // a file
FILE* file = stdout;                                      // standard output
FILE* file = fopen("/dev/usb/lp0", "w");                  // a usb printer
FILE* file = popen("/usr/bin/lpr -P PDF", "w");           // a PDF file
FILE* file = fdopen(socket(AF_INET,SOCK_STREAM,0), "r+"); // network socket

fprintf(file, "Hello World.\n");
answered Jun 21 by Damon
• 3,580 points

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