Manipulators

Manipulators

• Manipulators are the operators in C++ that are used for formatting the output. Various commonly used manipulators are setw, endl and setfill.

• The setw is used to set the minimum field width. We can set the right justified numbers using setw operator. Note that the setw function is defined in <iomanip.h> file.

C++ Program

#include<iostream>

#include<iomanip>

using namespace std;

int main()

{

int a=4444,b=22,c=333;

cout<<"Using setw(30)\n";

cout<<setw(30)<<a<<"\n";

cout<< setw(30)<<b<<"\n";

cout<< setw(30)<<c<<"\n";

cout<<"Using setw(20)\n";

cout<<setw(20)<<a<<"\n";

cout<<setw(20)<<b<<"\n";

cout<<setw(20)<<c<<"\n";

cout<<"Using setw(10)\n";

cout<<setw(10)<<a<<"\n";

cout<<setw(10)<<b<<"\n";

cout<< setw(10)<<c<<"\n";

retrun 0;

}

Output

Using setw(30)

4444

22

333

Using setw(20)

4444

333

22

Using setw(10)

4444

22

333

• The functionality of endl is similar to "\n" i.e. newline character.

C++ Program

#include<iostream>

#include<iomanip>

using namespace std;

int main()

{

cout<<"This is first line"<<endl;

cout<<"This is second line"<<endl;

cout<<"This is third line"<<endl;

cout<<"This is forth line"<<endl;

return 0;

}

Output

This is first line

This is second line

This is third line

This is forth line

•  The setfill manipulator is used to fill the fields entirely using some character specified within it.

C++ Program

#include<iostream>

#include<iomanip>

using namspace std;

int main()

{

int a=4444,b=22,c=333;

cout<<setw(10)<<setfill('*')<<a<<endl;

cout<<setw(10)<<setfill('*')<<b<<endl;

cout<<setw(10)<<setfill('*')<<c<<endl;

retrun 0;

}

Output

******4444

********22

*******333

 

Example:1

 i) Write output for the following (Assume all libraries has been included):

1. int main()

{

    float f = ‒76.54321;

    cout.fill ('*');

    cout.precision(3);

    cout.setf(ios::internal, ios::adjustfield);

    cout.setf(ios::scientific, ios:floatfield);

    cout.width(15);

    cout << f<< "\n";

}

2. int main()

{

    float f = 123.4;

    cout.setf(ios::showpoint);

    cout.setf(ios::showpos);

    cout.precision(3);

    cout.setf(ios::fixed, ios::floatfield);

    cout.setf(ios::internal, ios:adjustfield);

    cout.width(10);

    cout << f << "\n";

}

Solution :

We will include two library files namely iostream.h and iomanip.h

1. ‒ ****7.654e+001

2. + 123.400

 

Example:2

Write a program which reads the information like name, age and weight of ten people from the keyboard and displays it on the screen in four columns: Sr. No, Name, Weight and Age. Strings should be left‒justified and numbers should be right‒justified in a suitable field width.

Solution :

#include <iostream>

#include<iomanip>

using namespace std;

#define MAX 10

class student

{

    private:

      char Name[30];

      int age;

      float weight;

    public:

      void getDetails(void);

      void putDetails(int);

};

//member function definition, outside of the class

void student::getDetails(void)

{

      cout << "Enter name:

      cin >> Name;

      cout << "Enter age: ";

      cin >> age;

      cout << "Enter Weight:

      cin >> weight;

}

//member function definition, outside of the class

void student::putDetails(int sr_No)

{

      cout <<"\n"<<< setw(5)<<left<<sr_No

      <<<setw(8)<<left<< Name

      <<< setw(8) <<right<< age

      << setw(8) <<right<< weight;

}

int main()

{

student std[MAX];    //array of objects creation

int n,i;

cout << "Enter total number of students:

cin >> n;

for(i=0;i<n;i++)

{

      cout << "Enter details of person " << i+1 << ":\n";

      std[i].getDetails();

}

cout << endl;

cout<<"\n Sr.\tName\tAge\tWeight";

for(i=0;i< n; i++)

{

      std[i].putDetails(i+1);

}

return 0;

}

 

Example:3

What is basic difference between manipulators and ios member functions in implementation? Give examples.

Solution:

1)The ios function returns a value while manipulators does not.

2) There are standard ios functions we can have them user defined, while our own standard ios functions we can have them user manipulators can be created.

3) The ios function needs <iostream> while manipulators need <iomanip>

4) The ios functions are single and cannot be combined, while it is possible to specify the manipulators in chain.

Examples of ios are ‒

i) cout   ii) cin    iii) cerr    iv) clog

Examples of manipulators ‒

i) endl    ii) setw    iii) setfill    iv) ws

 

Review Questions

1. Explain manipulators.

2. List ios functions with equivalent manipulators in C++. Explain any one manipulator with example.