#include <iostream>
#include <iomanip>
using namespace std;


struct prec
{
    prec(int x) : prec_(x) {}
    int prec_;
};

ostream& operator<<(ostream& out, const prec& obj)
{
    out.precision(obj.prec_);
    return out;
}

class dollar
{
    double amount;
public:
    dollar(double amt) : amount(amt) {}
    friend ostream& operator<<(ostream& out, const dollar& obj);
};

ostream& operator<<(ostream& out, const dollar& obj)
{
    out << '$';
    auto currentFlags = out.flags() ;
    auto currentPrecision = out.precision();
    out << fixed << setprecision(2) << obj.amount;
    out.flags(currentFlags);
    out.precision(currentPrecision);
    return out;
}


class format
{
    int width;
    int decimalPlaces;
public:
    format(int arg1, int arg2 = -1);
    friend ostream& operator<<(ostream& out, const format& obj);
};

format::format(int arg1, int arg2)
: width(arg2 == -1 ? 0: arg1), decimalPlaces(arg2 == -1 ? arg1: arg2)
{ }

ostream& operator<<(ostream& out, const format& obj)
{
    out << fixed << setw(obj.width) << setprecision(obj.decimalPlaces);
    return out;
}

int main( )
{
    double pi = 3.141592654;
    cout << prec(4) << pi << endl;
    cout << prec(6) << pi << endl;
    cout << prec(0) << pi << endl;
    cout << dollar(pi) << endl;
    cout << pi << endl;
    cout << "-----------------" << endl;

    // print with a width of 5 and 2 decimal places
    cout << '/' << format(5,2) << pi << '/' << endl;

    // print with a width of 12 and 4 decimal places
    cout << '/' << format(12,4) << pi << '/' << endl;

    // print with 1 decimal place
    cout << '/' << format(1) << pi << '/' << endl;
}