std::setbase, std::setw , std::setfill in C++

The useful input/output manipulators are std::setbase, std::setw and std::setfill. These are defined in and are quite useful functions. 

• std::base : Set basefield flag; Sets the base-field to one of its possible values: dec, hex or oct according to argument base.
  Syntax : 

std::setbase (int base);
decimal : if base is 10
hexadecimal : if base is 16
octal : if base is 8
zero : if base is any other value.

• Implementation : This code uses the std::setbase manipulator to set hexadecimal as the base field selective flag.

CPP

// CPP Program to illustrate
// std::setbase manipulator
#include <iostream>
#include <iomanip> // std::setbase

int main()
{
    // set base to hexadecimal
    std::cout << std::setbase(16);

    // displaying 255 in hexadecimal
    std::cout << 255 << std::endl;

    // set base to Octal
    std::cout << std::setbase(8);

    // displaying 255 in Octal
    std::cout << 255 << std::endl;
    return 0;
}

• Output:

ff
377

• std::setw : Set field width; Sets the field width to be used on output operations. Behaves as if member width were called with n as argument on the stream on which it is inserted/extracted as a manipulator (it can be inserted/extracted on input streams or output streams). 
  Syntax : 

std::setw (int n);
where n is Number of characters to 
be used as field width.

CPP

// CPP Program to illustrate
// std::setw manipulator
#include <iostream>
#include <iomanip> // std::setw

int main()
{

    // set width of 10
    std::cout << std::setw(10);
    std::cout << 100 << std::endl;

    std::string str = "GFG";

    // set width of 12
    std::cout << std::setw(12);

    std::cout << str << std::endl;
    return 0;
}

• Output:

       100
         GFG

• Note: Here argument given to setw() is minimum width of the output, so if we have output with more width than argument’s value then output width will not be exactly the argument given to setw() but will be equal to the output size(i.e., the output will not get truncated). Default width of setw() is 0.
  Example:

CPP

#include <iostream>
#include<iomanip>
#include<string>
using std::cout;
using std::string;
using std::endl;

int main() {
    string temp="Hello setw";
    cout<<std::setw(5)<<temp<<endl;
    return 0;
}

• Output:

Hello setw

• std::setfill : Set fill character; Sets c as the stream’s fill character. Behaves as if member fill were called with c as argument on the stream on which it is inserted as a manipulator (it can be inserted on output streams).
  Syntax : 

std::setfill (char_type c);
char_type is the type of characters 
used by the stream (i.e., its first class template 
parameter, charT).

• Implementation : 

CPP

// CPP Program to test std::setfill manipulator
#include <iostream>
#include <iomanip> // std::setfill, std::setw

int main()
{
    // setfill is x and width is set as 10
    std::cout << std::setfill('x') << std::setw(10);

    std::cout << 77 << std::endl;

    std::string str = "Geeks";

    // setfill is G and width is set as 10
    // And std::left is used set str to left side
    std::cout << std::left << std::setfill('G') << std::setw(10);

    std::cout << str << std::endl;
    return 0;
}

• Output: 

xxxxxxxx77
GeeksGGGGG

Pattern using std::setw and std::fill : 

CPP

// CPP Program to print
// pattern using std::setw and std::fill
#include <iostream>
#include <iomanip> // std::setfill, std::setw

int main()
{
    int n = 5;
    for (int i = 1; i <= n; i++) {
        std::cout << std::left << std::setfill(' ') << std::setw(n);
        std::cout << std::string(i, '*') << std::endl;
    }
}

Output:

*
**
***
****
*****

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