Output of C++ Program | Set 6

　　Predict the output of below C++ programs.

Question 1

 1 #include<iostream>
 2
 3 using namespace std;
 4
 5 class Test
 6 {
 7     int value;
 8 public:
 9     Test (int v = 0)
10     {
11         value = v;
12     }
13     int getValue()
14     {
15         return value;
16     }
17 };
18
19 int main()
20 {
21     const Test t;
22     cout << t.getValue();
23     return 0;
24 }

　　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.

 1 #include<iostream>
 2
 3 using namespace std;
 4
 5 class Test
 6 {
 7     int value;
 8 public:
 9     Test (int v = 0)
10     {
11         value = v;
12     }
13     int getValue() const
14     {
15         return value;
16     }
17 };
18
19 int main()
20 {
21     const Test t;
22     cout << t.getValue();
23     return 0;
24 }

Question 2

 1 #include<iostream>
 2 using namespace std;
 3
 4 class Test
 5 {
 6     int &t;
 7 public:
 8     Test (int &x)
 9     {
10         t = x;
11     }
12     int getT()
13     {
14         return t;
15     }
16 };
17
18 int main()
19 {
20     int x = 20;
21     Test t1(x);
22     cout << t1.getT() << " ";
23     x = 30;
24     cout << t1.getT() << endl;
25     return 0;
26 }

　　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″.

 1 #include<iostream>
 2
 3 using namespace std;
 4
 5 class Test {
 6     int &t;
 7 public:
 8     Test (int &x):t(x) {  }
 9     int getT() { return t; }
10 };
11
12 int main() {
13     int x = 20;
14     Test t1(x);
15     cout << t1.getT() << " ";
16     x = 30;
17     cout << t1.getT() << endl;
18     return 0;
19 }

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　　2013-11-27　　15:27:57