outputting values from class

[dubley]

Hello, in this program, when I output total_val I get 0, when it should be 500 and 21. I can get the program to work if I write an external function but not when I put the function definition within the class.

This is the output:
Stock holdings:
Company: Apple
Numshares: 10
Price: 50
Total price: 0
Company: Micro
Numshares: 7
Price: 3
Total price: 0

  #include <iostream>		
#include <string>		
using namespace std;
class Stock
{
private:
	string company;
	int numshares;
	double price;
public:
	Stock(const string & co, long n = 0, double p = 0.0);
	void show();
	double total_val;
	void set_tot() { total_val = numshares * price; }
};
const int numarr = 2;
int main()
{
	Stock stocks[numarr] = { Stock("Apple", 10, 50.00),
		Stock("Micro", 7, 3.00) };
	cout << "Stock holdings:\n";
	stocks[0].show();
	stocks[1].show();
	return 0;
}
Stock::Stock(const string & co, long n, double p)
{
	company = co;
	numshares = n;
	price = p;
	total_val = 0.0;
}
void Stock::show()
{
	cout << "Company: " << company << endl;
	cout << "Numshares: " << numshares << endl;
	cout << "Price: " << price << endl;
	cout << "Total price: " << total_val << endl;
}

[kbw]

You assigned it zero. Perhaps you should assign it the value of p* n.

[Repeater]

total_val = 0.0;

This is the code that sets total_val.

You never change total_val.

Did you mean to call the function set_tot? You never call it.

[dubley]

Hi, thanks very much for the replies. If I don't set total_val, I get this output:
Stock holdings:
Company: Apple
Numshares: 10
Price: 50
Total price: -9.25596e+61
Company: Micro
Numshares: 7
Price: 3
Total price: -9.25596e+61

If I assign the value to p* n it works but I am trying to keep the calculation definition within the class because I am trying to break down another program to understand how it works, which is also the reason for the uncalled set_tot. This is the original program.

#ifndef STOCK20_H_	
#define STOCK20_H_	
#include <string>	
class Stock	
{	
private:	
	std::string company;
	int shares;
	double share_val;
	double total_val;
	void set_tot() { total_val = shares * share_val; }
public:	
	Stock(); // default constructor
	Stock(const std::string & co, long n = 0, double pr = 0.0);
	~Stock(); // do-nothing destructor
	void buy(long num, double price);
	void sell(long num, double price);
	void update(double price);
	void show()const;
	const Stock & topval(const Stock & s) const;
};	
#endif	

#include <iostream>	
#include "stock20.h"	
// constructors	
Stock::Stock() // default constructor	
{	
	company = "no name";
	shares = 0;
	
	total_val = 0.0;
}	
Stock::Stock(const std::string & co, long n, double pr)	
{	
	company = co;
	if (n < 0)
	{
	}
	else
	share_val = pr;
	set_tot();
}	
// class destructor	
Stock::~Stock() // quiet class destructor	
{	
}	
// other methods	
void Stock::buy(long num, double price)	
{	
	if (num < 0)
	{
	}
	else
	{
	}
}	
void Stock::sell(long num, double price)	
{	
	using std::cout;
	if (num < 0)
	{
	}
	else if (num > shares)
	{
	}
	else
	{
	}
}	
void Stock::update(double price)	
{	
	share_val = price;
	set_tot();
}	
void Stock::show() const	
{	
	using std::cout;
	using std::ios_base;
	// set format to #.###
	ios_base::fmtflags orig =
	std::streamsize prec = cout.precision(3);
	cout << "Company: " << company
	cout << " Share Price: $" << share_val;
	// set format to #.##
	cout.precision(2);
	cout << " Total Worth: $" << total_val << '\n';
	// restore original format
	cout.setf(orig, ios_base::floatfield);
	cout.precision(prec);
}	
const Stock & Stock::topval(const Stock & s) const	
{	
	if (s.total_val > total_val)
	else
}	

#include <iostream>		
#include "stock20.h"		
const int STKS = 4;		
int main()		
{		
	// create an array of initialized objects	
	Stock stocks[STKS] = {	
		Stock("NanoSmart", 12, 20.0),
		Stock("Boffo Objects", 200, 2.0),
		Stock("Monolithic Obelisks", 130, 3.25),
		Stock("Fleep Enterprises", 60, 6.5)
	};	
	std::cout << "Stock holdings:\n";	
	int st;	
	for (st = 0; st < STKS; st++)	
		stocks[st].show();
	// set pointer to first element	
	const Stock * top = &stocks[0];	
	for (st = 1; st < STKS; st++)	
		top = &top->topval(stocks[st]);
		// now top points to the most valuable holding
		std::cout << "\nMost valuable holding:\n";
	top->show();	
	return 0;	
}		

[Repeater]

So what's the actual question, then?

You say that you're choosing to set total_val to zero, and you're choosing not to change it after that? So you're choosing for it to be zero, and it is zero? So what's the problem?

[dubley]

In the original program, line 87:
cout << " Total Worth: $" << total_val << '\n';
outputs the correct values. I set it to zero just as a way to initialise it. I can see that was unneeded. My question is how do I output the correct values, that is 500 and 21, for total price, using a similar style as the original program I am breaking down? That has at line 11:
void set_tot() { total_val = numshares * price; }
in the class and
cout << " Total Worth: $" << total_val << '\n';
in void Stock::show() const

[Repeater]

The obvious way is to do something that sets total_val to the correct value.

The class contains a function you can call that will do that.

stocks[0].set_tot();

[sahil9620]

#include <iostream>
#include <string>
using namespace std;
class Stock
{
private:
string company;
int numshares;
double price;
public:
Stock(const string & co, long n = 0, double p = 0.0);
void show();
double total_val;
void set_tot() { total_val = numshares * price; }
};
const int numarr = 2;
int main()
{
Stock stocks[numarr] = { Stock("Apple", 10, 50.00),
Stock("Micro", 7, 3.00) };
cout << "Stock holdings:\n";
stocks[0].show();
stocks[1].show();
return 0;
}
Stock::Stock(const string & co, long n, double p)
{
company = co;
numshares = n;
price = p;
total_val = n*p;
}
void Stock::show()
{
cout << "Company: " << company << endl;
cout << "Numshares: " << numshares << endl;
cout << "Price: " << price << endl;
cout << "Total price: " << total_val << endl;
}


try this

This is the output:
Stock holdings:
Company: Apple
Numshares: 10
Price: 50
Total price: 500
Company: Micro
Numshares: 7
Price: 3
Total price: 21

[dubley]

Hi, I got it working in the style of the original program. Thank you very much for your help.

Stock::Stock(const string & co, long n, double p)
{
	company = co;
	numshares = n;
	price = p;
	set_tot();
}
void Stock::show()
{
	cout << "Company: " << company << endl;
	cout << "Numshares: " << numshares << endl;
	cout << "Price: " << price << endl;
	cout << "Total price: " << total_val << endl;
}