C++ Switch Structure (Running Last Case Twice)

Question

#include <iostream>
#include <iomanip>
#include <fstream>

using namespace std;

//Named constants residential customers
const double RES_BILL_PROC_FEES = 4.50;
const double RES_BASIC_SERV_COST = 20.50;
const double RES_COST_PREM_CHANNEL = 7.50;

//Named constants business customers
const double BUS_BILL_PROC_FEES = 15.00;
const double BUS_BASIC_SERV_COST = 75.00;
const double BUS_BASIC_CONN_COST = 5.00;
const double BUS_COST_PREM_CHANNEL = 50.00;

int main()
{
   //Variable declarations
    int accountNumber;
    char customerType;
    int numOfPremChannels;
    int numOfBasicServConn;
    double amountDue;

    //declaring file streams
    ifstream inFile;
    ofstream outFile;

    //open the file streams
    inFile.open("input.txt");
    outFile.open("output.txt");

    //check wheather file exists or not
    if (inFile.fail())
    {
        cout << "The input file cannot be found! ";
        return 1;
    }

    //output console message
    cout << "\n==========================================\n\n";
    cout << "     PROGRAM TO COMPUTE THE CABLE BILL\n";
    cout << "\n==========================================\n\n";
    //output outfile message
    outFile << "\n==========================================\n";
    outFile << "              Customer Details";
    outFile << "\n==========================================\n";

    //loop until end of file
    while (!inFile.eof())
    {
    cout << "The account number is: ";
    inFile >> accountNumber;
    cout << accountNumber<<"\n";

    cout << "The customer type: "
         << "R or r (Residential), "
         << "B or b (Business):  ";
    inFile >> customerType;
    cout << customerType << endl;

    //switch to residential or business customer type
    switch (customerType)
        {
        case 'r':
        case 'R':
            cout << "Enter the number"
                 << " of premium channels: ";
            cin >> numOfPremChannels;
            cout << "\n\n";

            amountDue = RES_BILL_PROC_FEES
                       + RES_BASIC_SERV_COST
                       + numOfPremChannels *
                         RES_COST_PREM_CHANNEL;
            //write to output file
            outFile << setw(25) << left << "\nCustomer Account Number: "
                    << accountNumber << endl;
            outFile << setw(25) << left << "Amount Due: "
                    << fixed << setprecision(2) << "$" << amountDue << endl;

            break;

        case 'b':
        case 'B':
            cout << "Enter the number of basic "
                 << "service connections: ";
            cin >> numOfBasicServConn;


            cout << "Enter the number"
                 << " of premium channels: ";
            cin >> numOfPremChannels;
            cout << "\n\n";

            if (numOfBasicServConn <= 10)
                amountDue = BUS_BILL_PROC_FEES
                            + BUS_BASIC_SERV_COST
                            + numOfPremChannels *
                              BUS_COST_PREM_CHANNEL;
            else
                amountDue = BUS_BILL_PROC_FEES
                            + BUS_BASIC_SERV_COST
                            + (numOfBasicServConn - 10) *
                               BUS_BASIC_CONN_COST
                            + numOfPremChannels *
                              BUS_COST_PREM_CHANNEL;

            //write to output file
            outFile << setw(25) << left << "\nCustomer Account Number: "
                    << accountNumber << endl;
            outFile << setw(25) << left << "Amount Due: "
                    << fixed << setprecision(2) << "$" << amountDue << endl;

            break;

        default:
            //write to output file
            outFile << "\nThe account number " << accountNumber << " has an invalid customer type." << endl;

            break;
        } //end switch

    } //end eof while loop

    //close input file
    inFile.close();

    //close output file
    outFile.close();

    return 0;
}

Can anyone explain to me why the last case is always being run/printed twice? This is a basic program we have to write for class and I can't seem to get why it's not working. Do I have a problem in my .eof() while loop? I've tried using a do-while loop but I'm getting the same result. I've also tried changing the input file by not including a default case but it's still running the last set twice.

**For the the number of basic connections and channels, just input any valid integer This is my input file:

157744232 b
253453534 r
335345435 R
445345345 B
545345345 t

C++ is pretty heavy-handed for a problem like this. Why not Python, Ruby or even NodeJS? — tadman, Sep 25 '13 at 19:47
@tadman If he's taking a C++ class, I don't think he would get a good grade by turning in a Python answer. — Barmar, Sep 25 '13 at 19:50
possible duplicate of [.eof() loop not working](http://stackoverflow.com/questions/8734116/eof-loop-not-working) — Barmar, Sep 25 '13 at 19:50

score 4 · Answer 1 · answered Sep 25 '13 at 19:50

This is not because of the switch structure, it's because of the eof call: the function starts returning true only after an unsuccessful attempt at reading the next item.

Change the loop to an infinite one (for (;;) or while(true), it does not matter) and perform the check for eof after reading the data. If you get a true, use break to end the loop. Otherwise, proceed to your switch statement.

The structure of your loop should be like this:

for (;;) {
    cout << "The account number is: ";
    if (!(inFile >> accountNumber))
        break;
    cout << accountNumber<<"\n";
    cout << "The customer type: "
         << "R or r (Residential), "
         << "B or b (Business):  ";
    if (!(inFile >> customerType))
        break;
    cout << customerType << endl;
    switch (customerType) {
        ... // The rest of your code
    }
}

score 1 · Answer 2 · answered Sep 25 '13 at 19:54

1

When you write a loop on a file you should use something like this:

while( inFile >> somevar ) {
   ...
}

or this:

while( true ) {
   inFile >> somevar1;
   if( !inFile ) break;
   ...
}

This is common mistake.

answered Sep 25 '13 at 19:54

Slava

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C++ Switch Structure (Running Last Case Twice)

2 Answers2