Using various format specifiers of c in c++

Question

As in c we can use various format specifiers like

• %nd where n is a number, to print the number with a total of atleast n space covered
• %0nd same as above, except pre-padding with 0's " %05d ",3 => 00003
• %.nf to set precision of n after decimal
• etc ....

So is there any way to use these with std::cout ?

I got some negative feedback in a recent course (c++ for c programmers) in coursera, for using printf instead of cout because i wanted to some formatting :(

Answer 1

For %nd %0nd, C++ equivalents are std::setw() and std::setfill().

#include <iostream>     // std::cout, std::endl
#include <iomanip>      // std::setfill, std::setw

int main () {
  std::cout << std::setfill ('x') << std::setw (10);
  std::cout << 77 << std::endl;
  return 0;
}

Output: xxxxxxxx77

%.nf can be replaced by std::setprecision and std::fixed,

#include <iostream>     // std::cout, std::fixed, std::scientific

int main () {
    double a = 3.1415926534;
    double b = 2006.0;
    double c = 1.0e-10;

    std::cout.precision(5);

    std::cout << "fixed:\n" << std::fixed;
    std::cout << a << '\n' << b << '\n' << c << '\n';
    return 0;
}

Output:

fixed:
3.14159
2006.00000
0.00000