[Omegaclass]

Hi Gentlemen and Ladies,

i am trying to find a way to read a file and perform mathematics on the numbers dose anyone know how i should proceed on this.

#include "stdafx.h"
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

struct car 
{
	
	int car_no;   
	int  milesDr;		
	int  gallons;  
};

int main()
{
	const int reports = 5;
	int temp_mpg = 0;
	int goallonsTotal = 0;
	int miles_total = 0;

	car records[reports] = 
	{
		{25, 1450, 62},
		{36, 3240, 136},
		{44, 1769, 67},
		{52, 2360, 105},
		{68, 2115, 67}
	};


cout << endl;

cout << setiosflags(ios::left);
for (int i = 0; i < reports; i++)
{
	cout << setw(8)<<"Car ID: " << records[i].car_no;
	cout << setw(18)<<"  Miles per gallon: "<< records[i].milesDr/records[i].gallons << endl;
	temp_mpg += records[i].milesDr/records[i].gallons;
}
cout << "Average miles per gallon of fleet is: " << temp_mpg/reports << endl;


system ("pause");

	return 0;
}

the above data in this program will need to be read from a file and do the same thing.

where should i go to find the answers to this solution, i don't think i need any code from anyone but a good resource to educate myself will be of great help and much appreciated.

thanks guys.

This post has been edited by Omegaclass: 13 December 2009 - 08:11 PM

[janotte]

Have a read here for info on File I/O
http://www.cplusplus...tutorial/files/

Feel free to ask any questions you have after reading that.

[Omegaclass]

i don't understand how to convert an element in a file to a int could you give an example code that could help?

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;


string filecars = "cars.dat";
int num;
long offset, last;
ifstream infile(filename.c_str())

infile.seekg(0L, ios::end);
last = infile.tellg();
for (offset = 4L; offset <= last; offset++)
{
infile.seekg(-offset, ios::end);
num = infile.get();
cout << num;
}
infile.close();
return 0;
}

This post has been edited by Omegaclass: 13 December 2009 - 10:59 PM

[Omegaclass]

sorry i mean "int" so i edited the post from char to int

[Ancient Dragon]

You need to post some of the contents of the data file. We can't really help a whole lot if we don't know what the file contains. If the file just contains numbers, then you probably don't have to use seekg() but just use >> to read the numbers, such as

int num;
while( inFile >> num ) // read all the numbers in the file
{
	// do something with the number
}

[Omegaclass]

Create a file containing the following: car numbers, miles driven, and gallons of gas used
in each car (do not include the readings):
Car Number, Miles Driven, Gallons Used
25 1450 62
36 3240 136
44 1769 67
52 2360 105
68 2115 67

reads the data in the file and displays the car number, miles driven,
gallons used and the miles per gallon for each car. The output should also contain the
total miles drive, total gallons used, and average miles per gallon for all the cars. These
totals should be displayed at the end of the output report.

here is the data i need to manipulate thanks for your input on this, i don't plan to sleep till this is done, i knovv you understand i am sure you have been there more then once, lol

[Ancient Dragon]

You need three integers, so just read all three in a loop

int carno, miles, gas;
while( infile >> carno >> miles >> gas)
{

}

This post has been edited by Ancient Dragon: 13 December 2009 - 11:29 PM

[Omegaclass]

Thank you very much, this hint may have saved me, thanks!

[Omegaclass]

sorry i just don't see how to make the while loop work and the program didn't open the file i placed in the folder any suggestion?

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;
int main () 
{

	string carfile = "fleet.txt";
	int nums, mpg, miles, carno, milesd, gas;
	long offset, last;
	ifstream infile (carfile.c_str());
	if (infile.fail())
	{ 
	cout << "error"<<endl;
	exit(1);
	}
	//infile.seekg(0L,ios::end);
	//last = infile.tellg();
		
while( infile >> carno >> miles >> gas)
{
cout << miles/gas;
}


	infile.close();
	system("pause");
	return 0;

}

[janotte]

Omegaclass, on 13 Dec, 2009 - 10:52 PM, said:

any suggestion?

Yes! I suggest you follow the advice given to you by Ancient Dragon here:

Ancient Dragon, on 13 Dec, 2009 - 10:01 PM, said:

You need to post some of the contents of the data file. We can't really help a whole lot if we don't know what the file contains.

Please share the first 5 lines of the text file you are working from.

[Omegaclass]

25 1450 62
36 3240 136
44 1769 67
52 2360 105
68 2115 67


this is the first 5 lines

[janotte]

When I compile your code I get these warnings that you should have a look at:

DIC.cpp: In function ‘int main()’:
DIC.cpp:10: warning: unused variable ‘nums’
DIC.cpp:10: warning: unused variable ‘mpg’
DIC.cpp:10: warning: unused variable ‘milesd’
DIC.cpp:11: warning: unused variable ‘offset’
DIC.cpp:11: warning: unused variable ‘last’

If I run your code (using the data you posted) I get this output:
2323262231

Is that what you expected?

Since I am having no problem opening the data file the first thing I suggest you check exactly where you saved the data file and exactly what name you gave it.

Can I also suggest that using "last" as a variable name is a bad idea.
Choose another name that isn't used by the C++ language for it's own purposes because using reserved words is a silly risk to take.

[Ancient Dragon]

I suspect he needs to add '\n' to separate the output cout << miles/gas << '\n';

[barnwillyb]

Omegaclass, on 13 Dec, 2009 - 10:52 PM, said:

sorry i just don't see how to make the while loop work and the program didn't open the file i placed in the folder any suggestion?

#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
using namespace std;
int main () 
{

	string carfile = "fleet.txt";
	int nums, mpg, miles, carno, milesd, gas;
	long offset, last;
	ifstream infile (carfile.c_str());
	if (infile.fail())
	{ 
	cout << "error"<<endl;
	exit(1);
	}
	//infile.seekg(0L,ios::end);
	//last = infile.tellg();
		
while( infile >> carno >> miles >> gas)
{
cout << miles/gas;
}


	infile.close();
	system("pause");
	return 0;

}

You might have to tell your computer where the file is using the folder name and then a slash line and then the name of the file like below:

//——————————————————————————————————————————————————————————
//						  includes
//——————————————————————————————————————————————————————————

#include <iostream>
#include <fstream>
#include <iomanip>

using namespace std;

/*__________________________________________________________*/
/*																													*/
/*											 main listing												*/
/*__________________________________________________________*/

int main (int argc, char * const argv[]) {
	int carno = 0;
	double mileage = 0.0, miles = 0.0, gas = 0.0;
	ifstream infile;

	// set precision to 2 decimals
	cout << setprecision( 2 ) << setiosflags( ios::fixed | ios::showpoint );

	infile.open("/Developer/Applications/Mac OS X Books/C++ Programming/Read Car Mileage/CarData.txt");

	if (infile.fail()) { 
	cout << "error" << endl;

	exit( 1 );
	}

	cout << endl;
	while (infile >> carno >> miles >> gas) {
		// do mileage calculations
		mileage = miles/gas;
		cout << "\t" << carno << "\t" << miles << "\t" << gas << endl;
		cout << "\tCar #" << carno << " drives " << miles << " miles and uses " << gas << " gallons of gas, " << "which is " << mileage << " miles per gallon." << endl << endl;
	}
	infile.close();
	
	return 0;
}

Hope that helps!

[Omegaclass]

thanks for the explanation this relay helped, but what dose the "\t" mean? and where do i go to find the references to this type of notation for example "%d" i sometimes see this in code and don't know understand it.

thanks guys

This post has been edited by Omegaclass: 18 December 2009 - 06:12 PM