# include <cstdlib>
# include <iostream>
# include <cmath>

using namespace std;

double f ( double x );

int main ( )
//
//  BRACKET is a program which allows the user to type in values of X
//  at which the value of F(X) should be printed.
//
//  The program continues to accept input until the user types CTRL-D.
//
//  This program uses the function F(X) = COS(X) - X as an example.
//
{
  double x;

  cout << "\n";
  cout << "BRACKET:\n";
  cout << "  Enter a value X, to receive a function value F(X).\n";
  cout << "  Terminate with a CTRL-D or end-of-file.\n";

  while ( true )
  {
    cin >> x;
    if ( cin.eof ( ) )
    {
      break;
    }
    cout << "  F(" << x << ") = " << f ( x ) << "\n";
  }
  return 0;
}
double f ( double x )
{
  double value;

  value = cos ( x ) - x;

  return value;
}