savings account problem

ap6118 · #1 31-Mar-2005, 16:27

I am trying to write a savings account program, and i did what i thought was the right thing.
suprise suprise, when the program runs i get weird results, as if the class objects are not being initialised by the constructor, since it is giving me weirds "garbage" numbers?
here are the class declaration and implementation files

CPP / C++ / C Code:

#ifndef SAVACC_H
#define SAVACC_H
#include <stdlib.h>
#include <ctime>
#include <iostream>

class SavingsAccount
{
public:
	SavingsAccount( double savingsBalance, double annualInterestRate );
	//constructor for the class
	//initializes the account balance to dollars
	//and the interest rate to rate percent.
	SavingsAccount();
	//initializes the account balance to zero
	//and the interest rate to zero.
	double get_balance();
	//returns the current account balance
	 double get_rate();
	//returns the current rate
	double calculateMonthlyInterest();
	//calculates monthly interest by multiplying
	// savingsBalance by the annualInterestRate divided by 12.
	 double modifyInterestRate();
	void printtestresults(SavingsAccount);
 
private:
	double savingsBalance;
	double annualInterestRate;//expressed as a percentage
};

#endif SAVACC_H

CPP / C++ / C Code:

#include <iostream>

using std::cout;
using std::cin;
using std::endl;
#include <stdlib.h>
#include <iomanip>

using std::setw;

#include <cstdlib>

#include <new>

#include "savingsaccount.h"

SavingsAccount::SavingsAccount( double savingsBalance, double annualInterestRate )
{
	savingsBalance = savingsBalance;
	annualInterestRate = annualInterestRate;
}

SavingsAccount::SavingsAccount()
{
	savingsBalance = 0.0;
	annualInterestRate = 0.0;
}

double SavingsAccount::get_balance()
{
	return savingsBalance;
}

double SavingsAccount::get_rate()
{
	return annualInterestRate;
}
double SavingsAccount::calculateMonthlyInterest()
{
   return ((savingsBalance * annualInterestRate)/12);
	
}
double SavingsAccount::modifyInterestRate()
{
	double rate = 0;
	rate = annualInterestRate;
	rate = rate +1;
	return rate;
}
void SavingsAccount::printtestresults(SavingsAccount joe)
{
    cout <<"balance = "<<savingsBalance<<endl;
	cout <<"annual Interest Rate : "<<annualInterestRate<<endl;
    cout <<"the monthly interest rate for this customer is :"<<endl;
	cout <<joe.calculateMonthlyInterest()<<endl;
}

CPP / C++ / C Code:

#include <iostream>

using std::cout;
using std::cin;
using std::endl;
#include <stdlib.h>
#include <ctime>

#include "savingsaccount.h"


int main()
{
	SavingsAccount saver1(2000.00,3.0);

	cout <<"saver1 is initialized as follows:\n";
	saver1.printtestresults(saver1);
	cout <<"saver1's new balance is : "<<(2000 + saver1.calculateMonthlyInterest());
	cout <<"saver1's interest for next month is : "<<saver1.modifyInterestRate<<endl;
	saver1.printtestresults(saver1);
	
	return 0;
}

davekw7x · #2 31-Mar-2005, 16:51

Quote:

Originally Posted by ap6118

I am trying to write a savings account program

**EDIT*** Note changes here

What compiler are you using? Borland compilers give warnings:

Quote:

Warning W8004 'annualInterestRate' is assigned a value that is never used in function SavingsAccount::SavingsAccount(double,double)
Warning W8004 'savingsBalance' is assigned a value that is never used in function SavingsAccount::SavingsAccount(double,double)

(I thought that other compilers would also give warnings, but apparently not)

Since your observation of program output makes you think the constructor is not initializing things properly, Look at your constructor:

CPP / C++ / C Code:

SavingsAccount::SavingsAccount( double savingsBalance, double annualInterestRate )
{
  savingsBalance = savingsBalance;
  annualInterestRate = annualInterestRate;
}

This does nothing! (The argument savingsBalance is used as source and target of the assignment. Same for annualInterestRate.)

You could do this:

CPP / C++ / C Code:

SavingsAccount::SavingsAccount( double savingsBalance, double annualInterestRate )
{
  SavingsAccount::savingsBalance = savingsBalance;
  SavingsAccount::annualInterestRate = annualInterestRate;
}

or something like this:

CPP / C++ / C Code:

SavingsAccount::SavingsAccount( double sBalance, double aInterestRate )
{
  savingsBalance = sBalance;
  annualInterestRate = aInterestRate;
}

Either will work. See the difference between these and what your constructor did?

Regards,

Dave

Regards,

Dave

ap6118 · #3 31-Mar-2005, 17:18

i am using visual studio 6
there are no compiler errors or warnings.
just the output of the program are garbage numbers.

exemple:

saver1 is initialised as followes:
balance = -9.25596+061 dollars
blah blah blh

davekw7x · #4 31-Mar-2005, 17:40

Quote:

Originally Posted by ap6118

i am using visual studio 6
there are no compiler errors or warnings.
just the output of the program are garbage numbers.

exemple:

saver1 is initialised as followes:
balance = -9.25596+061 dollars
blah blah blh

I edited my previous post to show some possibilities. I'm sorry that I didn't say these things at first, but I somehow thought there might have been some useful compiler messages. Sorry.

Try reading my edited post and see if it helps (and/or see if it makes sense). You definitely need to change your constructor

Regards,

Dave

ap6118 · #5 31-Mar-2005, 20:05

thank you it worked fine.i saw the problem with the constructor.it was basicaly doing nothing.but it's allright now.
and another thing.i tried something else,i tried to declare annualInterestRate as a static and have get_rate function to be a static member function, but when i run the program i get this message from the compiler

savingsaccount.obj : error LNK2001: unresolved external symbol "private: static double SavingsAccount::annualInterestRate" (?annualInterestRate@SavingsAccount@@0NA)
Debug/savingsaccount.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

the lines i am referring to in the class declaration are:

CPP / C++ / C Code:

static double get_rate();
	//returns the current rate

static double annualInterestRate;//expressed as a percentage

ps: does anybody know of a better compiler than visual studio,it's eally getting on my nerves!!

davekw7x · #6 01-Apr-2005, 09:37

Quote:

Originally Posted by ap6118

thank you it worked fine.i saw the problem with the constructor.it was basicaly doing nothing.but it's allright now.
and another thing.i tried something else,i tried to declare annualInterestRate as a static and have get_rate function to be a static member function, but when i run the program i get this message from the compiler

savingsaccount.obj : error LNK2001: unresolved external symbol "private: static double SavingsAccount::annualInterestRate" (?annualInterestRate@SavingsAccount@@0NA)
Debug/savingsaccount.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

I don't see the point of trying to make a member function static.

As for the variable:

in SavingsAccount.h you have

CPP / C++ / C Code:

private:
  double savingsBalance;
  static double annualInterestRate;//expressed as a percentage

Now, each instance of this class has its own savingsBalance, but there is only one annualInterestRate for all instances. This declaration does not actually allocate any memory for the variable. So in your SavingsAccount.cpp you have a line like this:

CPP / C++ / C Code:

double SavingsAccount::annualInterestRate;

Now, you realize that if you change annualInterestRate for a particular object (in an initializer or any other function), it will change for all instances, right?

Regards,

Dave

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savings account problem

sorry i should have thought of that

again,i'm in your debt.