C++ Programming homework help

[scoobydrvr]

Lame, I know, but I'm taking a summer class and i've got an assignment that has me stumped.

I've got to overload the += and -= operator so that I can increase the value of a variable within an object by a value. For example:

SavingsAccount saver1;
saver1 += 234;

This needs to increment a data member called savingBalance belonging to the class SavingsAccount.

Wikipedia and all other sources I've tried have failed me. I'm hoping there are some professionals here that can offer me a hand... please?

 

[autobahn70]

I took this my sophomore year, the only way I passed was with help from my roommate. sorry I cant help!

 

[scoobydrvr]

thanks... believe me, the only reason i'm taking it is because I have to. It doesn't help that the one guy I know in the class has his phone off and my textbook is useless...

 

[iRoNyX]

thanks... believe me, the only reason i'm taking it is because I have to. It doesn't help that the one guy I know in the class has his phone off and my textbook is useless...

A seasoned programmer/nerd here, this will be a good start for you to read:

C++ Operator Overloading Guidelines

Basically you'll want a function within your object similar to the following:

MyClass & MyClass:: operator+=(int addedValue) { // no space between :: and operator, had to do it to avoid smiley
// Do the member variable addition work here.
MyClass.yourVariable = MyClass.yourVariable + addedValue;
// or if you can "see" the variable globally
yourVariable = yourVariable + addedValue;
return *this;
}

Not gonna do the homework for you, but hope that helps!

-Dave

 

[scoobydrvr]

That helps immensely, but now I'm getting a syntax error "missing ' ; ' before ' . ' " on the line

SavingsAccount.savingBalance = SavingsAccount.savingBalace + addedValue;

It's producing two of those errors for this one line and I'm totally at a loss for this one...

 

[scoobydrvr]

fixed it.
Header:
class SavingsAccount
{
public:
...
SavingsAccount& operator +=(float newAdd)
...
}

.cpp:

SavingsAccount& SavingsAccount:: operator +=(newAdd)
{
savingBalance = savingBalance + newAdd;
return *this;
}


thanks dave for your help getting me started!

 

[scoobydrvr]

fixed it.
Header:
class SavingsAccount
{
public:
...
SavingsAccount& operator +=(float newAdd)
...
}

.cpp:

SavingsAccount& SavingsAccount:: operator +=(newAdd)
{
savingBalance = savingBalance + newAdd;
return *this;
}


thanks dave for your help getting me started!

 

[oso2k]

That helps immensely, but now I'm getting a syntax error "missing ' ; ' before ' . ' " on the line

SavingsAccount.savingBalance = SavingsAccount.savingBalace + addedValue;

It's producing two of those errors for this one line and I'm totally at a loss for this one...

I see a typo on the RHS.

If its an instance member variable, then you shouldn't be using the class name:

savingsBalance = savingsBalance + addedValue;

or

this.savingsBalance = this.savingsBalance + addedValue;

However, if the savingBalance variable is a static class member variable, then you have the appropriate syntax:

SavingsAccount.savingsBalance = SavingsAccount.savingsBalance + addedValue;

In ironyx's example above, you were supposed to choose one or the other. Instance variables (and objects) can be created multiple times in a program (say like a database or web site). Static class member variables can only be created once and are only accessed via the class (SavingsAccount.) (if the program can only access savings account).