NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/9154

Text File | 1996-08-05 | 4.7 KB | 170 lines

Path: dns.crocker.com!usenet
From: [e-mail]
Newsgroups: comp.lang.c++
Subject: PLEASE help newbie with text file question
Date: 28 Feb 1996 18:26:32 GMT
Organization: Crocker Communciations (crocker.com)
Message-ID: <4h26oo$[e-mail]>
Reply-To: [e-mail]
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I'm currently teaching myself c++, and am practicing using text files with the
following small program. This program contains a simple class which stores
information about a savings project. My problem is that the value I read in as
the position of 'balance' in the text file does not seem to be right. It seems
that I get different results if I use seekp or seekg with the same number. What
I see is that balance is properly written over 0(the first deposit), but that
additional deposits are places on the same line as the financial goal. (this is
followed by two eol chars, one from bal line, another from deposit).
I'm a sophmore in high school and would appreciate ANY suggestions. (the few
people I know that use c++ stay away from streams). This is NOT homework.
I program for fun.
I appologize for this lengthy post, but I honestly don't know how else to figure
out this problem.
    THANK YOU,
    John Szumowski
    [e-mail]
************************************************************************
#include <iostream.h>
#include <fstream.h>
#include <stdlib.h>
#include <values.h>
#include <ctype.h>

#define MAXREC 10
#define DATAF "record.txt"

class project {
    long bloc;
    char id[16];
    double balance,goal;
public:
    void getpos(long &num) {num = bloc; }
    void getbal(double &b) {b = balance;}
    double percomp(double b,double g) {return ((b/g)*100);}
    void deposit(double d) {balance += d; }
    friend istream &operator>>(istream &stream, project &ob);
    friend ostream &operator<<(ostream &stream, project ob);
    friend fstream &operator>>(fstream &stream, project &ob);
    friend fstream &operator<<(fstream &stream, project &ob);
};

istream &operator>>(istream &stream, project &ob)
{
    cout << "Enter a id for this project. (15 char max)\n";
    stream.ignore(MAXINT,'\n');
    stream.getline(ob.id,16);
    cout << "Now, enter the financial goal: $";
    stream >> ob.goal;
    ob.balance = 0.0;
    return stream;
}

ostream &operator<<(ostream &stream, project ob)
{
    cout << "ID: " << ob.id << endl;
    cout << "Goal: $" << ob.goal << endl;
    cout << "Balance: $" << ob.balance << endl;
    cout << "Percent Complete: " <<
        ob.percomp(ob.balance, ob.goal) << "%\n";
    return stream;
}

fstream &operator>>(fstream &stream, project &ob)
{
    if(!stream.eof()) {
        stream.getline(ob.id, 16);
        stream >> ob.goal;
        ob.bloc = stream.tellg();
        stream >> ob.balance;
        stream.ignore(MAXINT,'\n');
    }
    return stream;
}

fstream &operator<<(fstream &stream, project &ob)
{
    stream << ob.id << endl;
    stream << ob.goal << endl;
    ob.bloc = stream.tellp();
    stream << ob.balance << endl;
    return stream;
}

void menu(int &i)
{
    cout << "*** PROJECT OPTIONS ***\n";
    cout << "1. Create a new savings project\n";
    cout << "2. Deposit into an existing savings project\n";
    //MORE CHOICES...
    cout << "5. Quit\n";
    cout << "\nYour choice: ";
    cin >> i;
}

main()
{
    project fp[MAXREC];
    fstream fpdata;
    int numrec = 0,first_rec = 0,i;
    long location[MAXREC];

    //initialize array
    fpdata.open(DATAF,ios::in);
    if(!fpdata) {
        cout << "Unable to open data file!";
        exit(1);
    }
    if(fpdata.peek() == EOF) first_rec = 1;
    while(fpdata >> fp[numrec] && numrec < MAXREC) {
        fp[numrec].getpos(location[numrec]);
        numrec++;
    }
    fpdata.close();
    //main program
    do {
        menu(i);
        //new record
        if(i==1) {
            if(first_rec) fpdata.open(DATAF,ios::out);
            else fpdata.open(DATAF,ios::app);
            cin >> fp[numrec];
            fpdata << fp[numrec];
            fp[numrec].getpos(location[numrec]);
            numrec++;
            fpdata.close();
        }
        //deposit into an existing record
        else if(i==2) {
            char ans;
            int where = 0;
            double dep,bal;
            //show records and ask for the one to be deposited into
            do {
                cout << "record number: " << (where+1) << endl;
                cout << fp[where] << endl;
                cout << "Deposit into this record? y/n --->";
                cin >> ans;
                ans = toupper(ans);
                if(ans!='Y') where++;
            }while(where<numrec && ans!='Y');
            //if a record was chosen, ask for deposit and update file
            if(where!=numrec) {
                cout << "Amount to deposit: $";
                cin >> dep;
                fp[where].deposit(dep);
                fp[where].getbal(bal);
                //update bal line in text file
            //opening ios::out destroys previous records
                fpdata.open(DATAF,ios::in | ios::out);
                fpdata.seekp(location[where],ios::beg);
                fpdata << bal << endl;
                fpdata.close();
            }
        }
    } while(i!=5);
    return 0;
}
************************************************************************