std::setfill

std::setfill is a manipulator function in C++ that sets the fill character for output streams. It is used in conjunction with other output formatting functions like std::setw to specify the character that should be used to fill the empty spaces when values are printed with fixed width.

Here is an example of how std::setfill can be used:

#include <iostream>
#include <iomanip>

int main() {
  int number = 123;

  std::cout << "Default fill: " << std::setw(10) << number << std::endl;
  std::cout << "Set fill to '-': " << std::setfill('-') << std::setw(10) << number << std::endl;
  std::cout << "Set fill to '*': " << std::setfill('*') << std::setw(10) << number << std::endl;

  return 0;
}

Output:

Default fill:        123
Set fill to '-': ----123
Set fill to '*': *******123

In the example, std::setfill('-') and std::setfill('*') are used to set the fill character to '-' and '*', respectively. The std::setw(10) sets the width of the output to 10 characters.