Output of C++ Program | Set 6

Predict the output of below C++ programs.

Question 1

#include<iostream>   using namespace std;   class Test {     int value; public:     Test (int v = 0) {value = v;}     int getValue() { return value; } };   int main() {     const Test t;      cout << t.getValue();     return 0; }

Output: Compiler Error.

A const object cannot call a non-const function. The above code can be fixed by either making getValue() const or making t non-const. Following is modified program with getValue() as const, it works fine and prints 0.

#include<iostream>   using namespace std;   class Test {     int value; public:     Test (int v = 0) { value = v; }     int getValue() const { return value; } };   int main() {     const Test t;      cout << t.getValue();     return 0; }

Question 2

#include<iostream>   using namespace std;   class Test {     int &t; public:     Test (int &x) { t = x; }     int getT() { return t; } };   int main() {     int x = 20;     Test t1(x);     cout << t1.getT() << " ";     x = 30;     cout << t1.getT() << endl;     return 0; }

Output: Compiler Error
Since t is a reference in Test, it must be initialized using Initializer List. Following is the modified program. It works and prints “20 30″.

#include<iostream>   using namespace std;   class Test {     int &t; public:     Test (int &x):t(x) {  }     int getT() { return t; } };   int main() {     int x = 20;     Test t1(x);     cout << t1.getT() << " ";     x = 30;     cout << t1.getT() << endl;     return 0; }

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