Thread: Help with classes and addition!

Hi,

I am currently trying to do an assignment where I read in from a file, three variables from each line, add them together and then at the end basically add each column up.
We have to use classes.

Reading works, adding each line works, and writing all that to a file works.

However, adding each individual column gets me some really crazy and crappy stuff.

I have tried doing it with temp variables in my class, temp variables in my loop and out of my loop.
I either get odd results like “-9.25596e+061” or, results that appear to have worked correct but completely bad math.


Right now my code might look a little messy, because well I have tried 15 different things, and having to change stuff so much I did not want to waste the time of typing lots of nice comments and descriptive variable names. And right now my output it kinda messy, but it is pointless cleaning that up unless I can get it to add correct!

Here is my code:

Code:

#include <iostream>
#include <fstream>
#include <cmath>
#include <cstdlib>
using namespace std;


class SalesFigures
{

public:
	SalesFigures(double jan, double feb, double march_);
	SalesFigures();

	void write_out();
	void write_out_total();
	void math(double in, double in2, double in3);



private:
	double january;
	double febuary;
	double march;
	double jan_total;
	double feb_total;
	double march_total;
};



int main()
{


	double in_1,in_2,in_3;
	SalesFigures one;

//	double temp1, temp2, temp3;

	ifstream in_stream;
	in_stream.open("source.txt");
	
	


	while (! in_stream.eof())
	{

	
	in_stream >> in_1 >> in_2 >> in_3;


	one =SalesFigures(in_1,in_2,in_3) ;

	one.write_out();
	
	one.math(in_1,in_2,in_3);


	

	

//	temp1 = in_1 + temp1; 
//	temp2 = in_2 + temp2;
//	temp3 = in_3 + temp3;


		
	
	}



	one.write_out_total();

//	ofstream out_f;
//	out_f.open("output.txt",ios::app);

//	out_f << temp1 << " " << temp2 << " " << temp3;

	in_stream.close();

	system("pause");

	


	return 0;
}







SalesFigures::SalesFigures(double jan, double feb, double march_)
{

	january = jan;
	febuary = feb;
	march = march_;

}



SalesFigures::SalesFigures()
{
	january = 0;
	febuary = 0;
	march = 0;
	jan_total = 0;
	feb_total = 0;
	march_total = 0;



}


void SalesFigures::write_out()
{

	ofstream out_f;
	out_f.open("output.txt",ios::app);

	out_f << january << " " << febuary  << " " << march << " " << january + febuary + march << endl ;

	out_f.close();


}

void SalesFigures::math(double in, double in2, double in3)
{

	jan_total = (in + january);
	feb_total = (in2 + febuary);
	march_total = (in3 + march);

}



void SalesFigures::write_out_total()
{

	ofstream out_f;
	out_f.open("output.txt",ios::app);

	out_f << jan_total << " " << feb_total  << " " << march_total << " " << jan_total + feb_total + march_total << endl ;

	out_f.close();
}

As you will see some things commeted out that I tried.

The source file is currently hardcoded to source.txt, here is an example of it:

Code:

105.1 298.3 37998.4
644.9 5654.8 6654.2
65457.1 86465.1 96454.1

Any help would be much appericated!

Your problem is that you're not initialising some of the members of your class. Make sure that the thre argument constructor initialises the _total members.

Similarly, in your main() functio, when you uncomment the temp variables, make sure you initialise those.

Essentially, if you forget to initialise a variable, the value it gets can be junk. And when you add something to a junk value, you get another junk value.....

Grumpy:

Thank you for your input. Initializing the temp variables to zero makes it work properly with that method.

That is not the method of the assignment though, I am to use constructors (as you see I tried); I was just trying that because I could not get it to work the other way.

However, I still can not get the constructor method to work.

Before the while loop, I declare the class type SalesFigures of ‘one’. Should it not call the default constructor then? The default constrictor sets everything to zero including my _totals.

Then in the loop I call the constructor with three types of double, so it should only modify the three non _total variables.

But for some reason, when I then and go output the _total variables, the values are not correct. As in the addition is wrong?


hk_mp5kpdw:

Pretty much everything you said we just covered today in class. However, the assignment was assigned Tuesday, and people today asked if we could use this for the assignment and she said no, only what you had learned up until the assignment was made. She said she has a very specific reason and we will use the “better” method in the next project once we cover friend functions a little more.

How I am doing it is not all we learned, and I will not have every function open and close the files, but I tried breaking everything down because I can not get my addition to work properly!

But thanks for the input!

Originally Posted by Enahs

Thank you for your input. Initializing the temp variables to zero makes it work properly with that method.

That is not the method of the assignment though, I am to use constructors (as you see I tried); I was just trying that because I could not get it to work the other way.

However, I still can not get the constructor method to work.

Before the while loop, I declare the class type SalesFigures of ‘one’. Should it not call the default constructor then? The default constrictor sets everything to zero including my _totals.

The problem actually occurs because of the line;

Code:

one =SalesFigures(in_1,in_2,in_3) ;

which creates a temporary SalesFigures object using the three argument constructor (which will have three uninitialised members) and then assigns "one" so it is equivalent to that object. Hence "one" winds up with three members that contain junk.

Which is why I say you need to initialise all of the members in the three argument constructor, as well as in the default constructor.

Originally Posted by Enahs

Then in the loop I call the constructor with three types of double, so it should only modify the three non _total variables.

But for some reason, when I then and go output the _total variables, the values are not correct. As in the addition is wrong?

The offending line I described above is in the loop: you are reassigning the object.

The addition works find. When you add junk to anything you get junk.

The addition works find. When you add junk to anything you get junk.

I started over from scratch, with what you all said in mind.

It is very neat, and damn nice code now I might say. It is odd, but I now have a huge feeling of overwhelming satisfaction.

Thanks again man!