C++: Nesting of member functions

Nesting of member functions

You know that only the public members of a class can be accessed by the object of that class, using dot operator. However a member function can call another member function of the same class directly without using the dot operator. This is called as nesting of member functions.

Illustration 14.7 The use of Nesting of Member Function

A member function can call another member function of the same class for that you do not need an object.

#include<iostream>

using namespace std

class nest

{

      int a;

      int square_num( )

      {

           return a* a;

      }

      public:

      void input_num( )

      {

      cout<<”\nEnter a number ”;

      cin>>a;

      }

      int cube_num( )

      {

           return a* a*a;

      }

void disp_num()

{

      int sq=square_num();        //nesting of member function

      int cu=cube_num();  //nesting of member function

      cout<<”\nThe square of “<<a<<” is  ” <<sq;

      cout<<”\nThe cube of “<<a<<” is  ” <<cu;

}

};

int main()

{

      nest n1;

      n1.input_num();

      n1.disp_num();

      return 0;

}

Output:

Enter a number 5

The square of 5 is 25

The cube of 5 is 125

In the above program disp_num() function calls two other member function square_ num() and cube_num(). Both are defined in different visibility mode.

The Scope Resolution Operator

If there are multiple variables with the same name defined in separate blocks then :: (scope resolution) operator will reveal the hidden file scope(global) variable.

Illustration 14.8 The use of scope resolution operator

Recall :: is also used to identify the class to which a member function belongs to.

#include<iostream>

using namespace std;

int a=100;

class A

{

      int a;

      public:

void fun()

      {

      a=20;

      a+=::a;         //using global variable value

      cout<<a;

} };

int main()

{

      clrscr(); A a1;

      a1.fun();

      retun 0;

}

Output:

120

Recall :: is also used to identify the class to which a member function belongs to.

In the above program the class data member and the global variable have same name.

To use the global variable :: used.