// VirtualInserter - base USDollar on the base class
//                   Currency. Make the inserter virtual
//                   by having it rely on a virtual
//                   display() routine

#include <stdio.h>
#include <iostream.h>
#include <iomanip.h>

// Currency - represent any currency
class Currency
{
    friend ostream& operator<<(ostream& out, Currency& d);
  public:
    Currency(int p = 0, int s = 0)
    {
        nPrimary = p;
        nSecondary = s;
    }

    // rationalize - normalize the number of nCents by
    //               adding a dollar for every 100 nCents
    void rationalize()
    {
        nPrimary   += (nSecondary / 100);
        nSecondary %= 100;
    }

    // display - display the object to the
    //           given ostream object
    virtual ostream& display(ostream&) = 0;

  protected:
    int nPrimary;
    int nSecondary;
};

// inserter - output a string description
//            (this version handles the case of cents
//            less than 10)
ostream& operator<<(ostream& out, Currency& c)
{
    return c.display(out);
}

// define dollar to be a subclass of currency
class USDollar : public Currency
{
  public:
    USDollar(int d, int c) : Currency(d, c)
    {
    }

    // supply the display routine
    virtual ostream& display(ostream& out)
    {
        char old = out.fill();
        out << "$" 
            << nPrimary 
            << "."
            << setfill('0') << setw(2)
            << nSecondary;

        // replace the old fill character
        out.fill(old);

        return out;
    }
};

void fn(Currency& c, char* pszDescriptor)
{
    cout << pszDescriptor << c << "\n";
}

int main(int nArgc, char* pszArgs[])
{
    // invoke USDollar::display() directly
    USDollar d1(1, 60);
    cout << "d1 = " << d1 << "\n";

    // invoke the same function virtually
    // through the fn() function
    USDollar d2(1, 5);
    fn(d2, "d2 = ");

    return 0;
}