Output of C++ Program | Set 5

 

　　Difficulty Level: Rookie

　　Predict the output of below C++ programs.

Question 1

 1 #include<iostream>
 2 using namespace std;
 3 
 4 class Test 
 5 {
 6     int value;
 7 public:
 8     Test(int v);
 9 };
10 
11 Test::Test(int v) 
12 {
13     value = v;
14 }
15 
16 int main() 
17 {
18     Test t[100];
19     return 0;
20 }

　　Output: Compiler error

　　The class Test has one user defined constructor “Test(int v)” that expects one argument. It doesn’t have a constructor without any argument as the compiler doesn’t create the default constructor if user defines a constructor (See this).

　　Following modified program works without any error.

 1 #include<iostream>
 2 using namespace std;
 3 
 4 class Test 
 5 {
 6     int value;
 7 public:
 8     Test(int v = 0);
 9 };
10 
11 Test::Test(int v) 
12 {
13     value = v;
14 }
15 
16 int main() 
17 {
18     Test t[100];
19     return 0;
20 }

 

Question 2

 1 #include<iostream>
 2 using namespace std;
 3 int &fun() 
 4 {
 5     static int a = 10;
 6     return a;
 7 }
 8 
 9 int main() 
10 {
11     int &y = fun();
12     y = y +30;
13     cout << fun();
14     return 0;
15 }

　　Output: 40
　　The program works fine because ‘a’ is static. Since ‘a’ is static, memory location of it remains valid even after fun() returns. So a reference to static variable can be returned.

 

Question 3

 1 #include<iostream>
 2 using namespace std;
 3 
 4 class Test
 5 {
 6 public:
 7     Test();
 8 };
 9 
10 Test::Test()  
11 {
12     cout<<"Constructor Called \n";
13 }
14 
15 int main()
16 {
17     cout<<"Start \n";
18     Test t1();
19     cout<<"End \n";
20     return 0;
21 }

　　Output:
　　Start
　　End

　　Note that the line “Test t1();” is not a constructor call. Compiler considers this line as declaration of function t1 that doesn’t recieve any parameter and returns object of type Test.

 

 

 

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　　2013-11-27　　15:23:22

　　

转载于:https://www.cnblogs.com/iloveyouforever/p/3445777.html