Help with overloading

[toomanystars]

HI guys,

Working a problem from a rather old C++ book. Everything in the program works, except the overloaded functions (which were provided as part of the program).

The idea is to take two old ENglish sterling amounts, convert it a double, add the doubles and return the new Sterling object.

However, when I run the overloaded functions, the program returns a bunch of gibberish numbers.

I would like get some advice, before I move to the next step, that is define the overloaded functions more explicitly, ie. not using the doubles.

Any help would be greatly appriciated.

Thanks

class Sterling
{
public:
	Sterling(){}
	Sterling(double p, int s, int pe):pounds(p),shilling(s),pence(pe){}
	friend istream& operator>>(istream& in, Sterling& s);
	friend ostream& operator<<(ostream& out, Sterling& s);
	operator double();
	Sterling (double decpound);
	Sterling operator+(Sterling& s){
		return Sterling(double(Sterling(pounds,shilling,pence))+double(s));//problem here
	}
	Sterling operator-(Sterling& s){
		return Sterling(double(Sterling(pounds,shilling,pence))-double(s));
	}
	Sterling operator*(Sterling& s){
		return Sterling(double(Sterling(pounds,shilling,pence))*double(s));
	}
	Sterling operator/(Sterling& s){
		return Sterling(double(Sterling(pounds,shilling,pence))/double(s));
	}
private:
	int shilling, pence;
	double pounds;
};  

int main()
{
	char choice;
	Sterling one(4,10,12), two(12,4,8);

	cout.setf(ios::fixed);
	cout.setf(ios::showpoint);
	cout.precision(2);
	do
	{
		
		cout<<"First sterling value: "<<one<<endl<<endl;
		cout<<"Second sterling value: "<<two<<endl;
		Sterling add=one+two;//problem here
		cout<<add<<endl;
		
		cout<<"\n\nAgain (y/n): ";
		cin>>choice;
	}while(choice=='y');


	_getch();
	return 0;
}
Sterling::Sterling (double decpound)
{
	double decfrac, decshill,decpence;
	Sterling temp;

	temp.pounds=static_cast<double>(decpound);
	decfrac=decpound-temp.pounds;
	decshill=20*decfrac;

	temp.shilling=static_cast<double>(decshill);
	decfrac=decshill-temp.shilling;
	decpence=12*decfrac;

	temp.pence=static_cast<double>(decpence);

	decshill=static_cast<double>(decshill);
	

}
Sterling::operator double()
{
	return(static_cast<double>(pounds)+((static_cast<double>(shilling)/20)+(static_cast<double>(pence)/240)));
}
ostream& operator<<(ostream& out, Sterling& s)
{
	out<<"\x9c "<<s.pounds<<"."<<s.shilling<<"."<<s.pence;
	return out;
}

istream&  operator>>(istream& in, Sterling& s)
{
	cout<<"Enter the pounds: ";in>>s.pounds;
	while(s.pounds<0){
		cout<<"Pounds can't be less than zero, try again: ";
		in>>s.pounds;
	}
	cout<<"Enter the shillings: ";in>>s.shilling;
	while(s.shilling<0){
		cout<<"Shillings can't be less than zero, enter again: ";
		in>>s.shilling;
	}
	cout<<"Enter the pence: ";in>>s.pence;
	while(s.pence<0){
		cout<<"Pence can't be less than zero, enter again: ";
		in>>s.pence;
	}
	return in;
}

[ne555]

Sterling::Sterling (double decpound)
{
	double decfrac, decshill,decpence;
	Sterling temp;

	temp.pounds=static_cast<double>(decpound);
	decfrac=decpound-temp.pounds;
	decshill=20*decfrac;

	temp.shilling=static_cast<double>(decshill);
	decfrac=decshill-temp.shilling;
	decpence=12*decfrac;

	temp.pence=static_cast<double>(decpence);

	decshill=static_cast<double>(decshill);
}

¿when do you assign anything to the object being constructed?

¿Why so many casts?

[toomanystars]

I may have overdone the casts, now that you mention it.

But the Sterling::Sterling (double decpound) is working well, it does what it's supposed to. I don't think any assignment is needed, the constructor is simply used for conversion.

[ne555]

it does what it's supposed to

Nope, it does nothing.
That's why you are seeing garbage.

You never set to anything this->pounds

[toomanystars]

In the book I am reading that constructor is supposed to convert from double to class object, and it does that admirably. Can you tell me then what needs to be done. I have not covered "this->" although I think it has something to do with pointers.

Thanks

[naraku9333]

Your constructor Sterling(double) should be setting the classes private variables

	int shilling, pence;
	double pounds;

but it doesn't.

[toomanystars]

Thanks a lot naraku! You rock, damn program was a thorn in my side for the past day and a half. So inside a constructor, you can't (or should not) create a separate object ? You should only deal with private variables?

Thanks,

Mike

[naraku9333]

You can create as many temporaries as you want, it just doesn't make much sense. Also, the casts make no sense either, you are literally casting a double to a double.