Question

In program P83.cpp, make the above changes, save the program as ex83.cpp, compile and run the program and make sure the correct output is produced. Your input file, in_file.dat, will have four integer values representing the dollars and cents part of the first amount and the dollars and cents part of the second amount.

Example: for input $50.34 and $86.73, you may have:
50 34
86 73

Once your program has successfully compiled and run, overload the write_money function as well.

#include<iostream>
#include<cstdlib>
#include<fstream>
using namespace std;

class AltMoney
{
    public:
        AltMoney();
        friend void read_money(istream& ins, AltMoney& m);
        friend AltMoney operator +(AltMoney m1, AltMoney m2);
        friend void write_money(ofstream& ous, AltMoney m);
    private:
        int dollars;
        int cents;
};

void read_money(istream& ins, AltMoney& m);
void get_streams(ifstream& ins, ofstream& ous);
void write_money(ofstream& ous, AltMoney m);

int main( )
{
     ifstream ins;
    ofstream ous;
     AltMoney m1, m2, sum;

     get_streams(ins, ous);

     read_money(ins, m1);
     ous << "The first money is:";
     write_money(ous, m1);

     read_money(ins, m2);
     ous << "The second money is:";
     write_money(ous, m2);

     sum = m1+m2;
     ous << "The sum is:";
     write_money(ous, sum);

     ins.close();
     ous.close();

     return 0;
}

AltMoney::AltMoney()
{
}

void write_money(ofstream& ous, AltMoney m)
{
     ous << "$" << m.dollars << ".";
     if(m.cents <= 9)
         ous << "0"; //to display a 0 on the left for numbers less than 10
     ous << m.cents << endl;
}

AltMoney operator +(AltMoney m1, AltMoney m2)
{
     AltMoney temp;
     int extra = 0;
     temp.cents = m1.cents + m2.cents;
     if(temp.cents >=100){
         temp.cents = temp.cents - 100;
         extra = 1;
      }
      temp.dollars = m1.dollars + m2.dollars + extra;

      return temp;
}

void read_money(istream& ins, AltMoney& m)
{
     int d, c;
     ins >> d;
     ins >> c;
     if( d < 0 || c < 0)
     {
            cout << "Invalid dollars and cents, negative values\n";
            exit(1);
     }
     m.dollars = d;
     m.cents = c;
}

void get_streams(ifstream& ins, ofstream& ous)
{

    ins.open("in_file.dat");
    if(ins.fail())
   {
       cout << "Failed to open the input file. \n";
       exit(1);
    }

    ous.open("out_file.dat");
    if(ous.fail())
   {
       cout << "Failed to open the output file. \n";
       exit(1);
    }
}

We will overload the >> so that writing an object of type AltMoney can be done using >>.   In order to overload >> to read an object of type AltMoney, you need to make the following changes in the program.

1) In the class AltMoney, replace the read_money function with the operator >> as described below:
class AltMoney
{
    public:
        AltMoney();
        friend istream& operator >>(istream& ins, AltMoney& m);
        friend AltMoney operator +(AltMoney m1, AltMoney m2);
        friend void write_money(ofstream& ous, AltMoney m);
    private:
        int dollars;
        int cents;
};

2) Prototype (comes before the main function)
istream& operator >>(istream& ins, AltMoney& m);

3) In the main:
     get_streams(ins, ous);

     ins >> m1;
     ous << "The first money is:";
     write_money(ous, m1);

     ins >> m2;
     ous << "The second money is:";

4) replace read_money function with:
istream& operator >>(istream& ins, AltMoney& m)
{
int d, c;
     ins >> d;
     ins >> c;
     if( d < 0 || c < 0)
     {
            cout << "Invalid dollars and cents, negative values\n";
            exit(1);
     }
     m.dollars = d;
     m.cents = c;
    return ins;
}

Answer 1

The file is modified according to the specification and given below. When you run the code it expects that you have a file named in_file.dat. The program does not produce any output on screen but generates a file named out_file.dat. Please check out_file.dat for output from the program.

in_file.dat
========
50 34
86 73

ex83.cpp
=======
#include<iostream>
#include<cstdlib>
#include<fstream>
using namespace std;

class AltMoney
{
public:
AltMoney();
friend istream& operator >>(istream& ins, AltMoney& m);
friend AltMoney operator +(AltMoney m1, AltMoney m2);
friend void write_money(ofstream& ous, AltMoney m);
private:
int dollars;
int cents;
};

istream& operator >>(istream& ins, AltMoney& m);
void get_streams(ifstream& ins, ofstream& ous);
void write_money(ofstream& ous, AltMoney m);

int main( )
{
ifstream ins;
ofstream ous;
AltMoney m1, m2, sum;

get_streams(ins, ous);

ins >> m1;
ous << "The first money is:";
write_money(ous, m1);

ins >> m2;
ous << "The second money is:";
write_money(ous, m2);

sum = m1+m2;
ous << "The sum is:";
write_money(ous, sum);

ins.close();
ous.close();

return 0;
}

AltMoney::AltMoney()
{
}

void write_money(ofstream& ous, AltMoney m)
{
ous << "$" << m.dollars << ".";
if(m.cents <= 9)
ous << "0"; //to display a 0 on the left for numbers less than 10
ous << m.cents << endl;
}

AltMoney operator +(AltMoney m1, AltMoney m2)
{
AltMoney temp;
int extra = 0;
temp.cents = m1.cents + m2.cents;
if(temp.cents >=100){
temp.cents = temp.cents - 100;
extra = 1;
}
temp.dollars = m1.dollars + m2.dollars + extra;

return temp;
}

istream& operator >>(istream& ins, AltMoney& m)
{
int d, c;
ins >> d;
ins >> c;
if( d < 0 || c < 0)
{
cout << "Invalid dollars and cents, negative values\n";
exit(1);
}
m.dollars = d;
m.cents = c;
return ins;
}

void get_streams(ifstream& ins, ofstream& ous)
{

ins.open("in_file.dat");
if(ins.fail())
{
cout << "Failed to open the input file. \n";
exit(1);
}

ous.open("out_file.dat");
if(ous.fail())
{
cout << "Failed to open the output file. \n";
exit(1);
}
}

out_file.dat (produced by program)
===========
The first money is:$50.34
The second money is:$86.73
The sum is:$137.07