Homework problem...structures or arrays?

Hi. I'm new here. Im a senior in high school, and I skipped Computer Programming I, and went straight to Programming II. The problem is, I had never programmed in my life until yesterday - So I'm still getting the hang of things. I've got a problem for homework, but I dont know how I'd go about doing it. Suggestions and Ideas - please.

8. Three employees in a company are up for a special pay increase. You are given a file, Ch3_Ex8Data.txt, with the following data

Miller Andrew 65789.87 5
Green Sheila 75892.56 6
Sethi Amit 74900.50 6.1

Each input line consists of the employee's last name, first name, current salary, and precent pay increase. Write a program that reads data from the specified file and stores the output in the file Ch3_Ex8Output.dat. For each employee the days must be output in the following form: firstName, lastName, updatedSalary. Format the ouput of the decimal numbers to two decimal places.


I know how to input the file, and all the main basics of C++, but I dont understand how I can the program to like....loop for each person in the file? Maybe I'm not supposed to do that?


Any advice/help is appreciated.

Did they teach structures and arrays before loops?

I don't know how much you expect us to tell you when we know it's a homework problem, but I will tell you that, yes, you're supposed to loop for each entry and yes, you're supposed to store it in one of the two programming terms in your thread title.

I wouldn't store it in either... it's just a read, calculate, write program... nothing really fancy needed IMO

unless of course the assignment calls for it... but I didn't see that...

I've really got no idea what everyone else in my class has been taught. My teacher said this should be an easy program to refresh everyones memory about reading and writing from an external file. I've been looking stuff up for over 2 hours trying to find out how to do it. I just need some guidance on what to do/use.

The tutorials or FAQs or a C++ book might help.

just use a loop and file I/O... if you can't do the refresher work, how'd you get into a class that far above your level?

File I/O and loops tutorials. They might be hard to read if you've never done any programming before, though.

Quote:

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Originally Posted by major_small

just use a loop and file I/O...

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...and if you don't understand what this means, I'd say your best bet is to visit your guidance counselor tomorrow with a change course form, and get yourself into Programming I which you shouldn't have bypassed in the first place.

I'd suggest either dropping the class and starting with programming 1, or talk to the teacher and get a week or so extension and get a few books ("Teach Yourself C++ in 21 Days" is excellent to learn quickly) to get a grasp on things.

For recommended books, see the C++ Book Recommendations sticky: http://cboard.cprogramming.com/showthread.php?t=74078

Ah, I've got it figured out now. Problem is I was sitting here without a book. The teacher is cool, and she'll let me catch up, so it wont be a problem. The reason I didnt take Comp Programming 1 is because its mainly VB - they only touch only c++ basics at the end - and I have no interest in learning VB.

Books are essential. In fact, if you started a poll in General Discussions on how many books everyone owns, I'm sure the average would be over half a dozen.

Ideas why this doesnt work?

Code:

---

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

bool getEmp(ifstream& empFile, string& lastName, string& firstName,
            double& salary, double& raise);
           
void writeEmp(ofstream& newFile, string& firstName, string&lastName,
              double& updatedSalary);

void calcSalary(double salary, double raise, double updatedSalary);

using namespace std;

int main()
 { 
    cout << "Beginning employee salary updation.\n";           
    ifstream empFile ("Ch3_Ex8Data.txt");
    if (!empFile) {
    cerr << "The system was unable to open the file."; //error if file is in use.
    exit(100);  //if it is, terminate.
    }
    ofstream newFile ("Ch3_Ex8Output.dat")
    if (!newFile) {
    cerr << "They system was unable to open the file.";
    exit (102);
    }
   
 string firstName, lastName;
 double salary, raise, updatedSalary;
 
 while (getEmp  (empFile, lastName, firstName, salary, raise))
 {
      calcSalary (salary, raise, updatedSalary);
      writeEmp (newFile,  firstName, lastName, updatedSalary);
      } //end of while
     
 empfile.close();
 newfile.close();
 cout << "End of salary updation.\n";
return 0;

} //end of main


bool getEmp(ifstream&  empFile, string& lastName, string& firstName,
            double& salary, double& raise)
{         
            empFile >> lastName >> firstName >> salary >> raise;
            if (!empFile)
              return false;
            return true;
} //end getEmp

void calcSalary(double salary, double raise, double updatedSalary)
{
    updatedSalary = (((raise*.01)+1)*salary)
   
    return;
} //end calcSalary

void writeEmp(ofstream& newFile, string& firstName, string&lastName,
              double& updatedSalary)
{
              newfile << firstName;
              newfile.fill << (' ');
              newfile << lastName;
              newfile.fill (' ');
              newfile << updatedSalary;
              return;
} //end writeEmp

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Could you give a little more detail than "doesn't work"?

I'm getting errors such as

'ifstream' was not declared in this scope.


that along with all the rest of my variables and ofstream.



I pretty much suck at programming I guess.

Code:

---

bool getEmp(ifstream& empFile, string& lastName, string& firstName,
            double& salary, double& raise);
           
void writeEmp(ofstream& newFile, string& firstName, string&lastName,
              double& updatedSalary);

void calcSalary(double salary, double raise, double updatedSalary);

using namespace std;

---

ifstream, ofstream, and string are all part of the std namespace, so the compiler doesn't see them until after your using declaration. the simple fix is to put 'using namespace std' immediately after your includes.

>I pretty much suck at programming I guess.

Maybe, but I doubt you've been at it long enough to know that ;)

Quote:

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Originally Posted by tortan

I pretty much suck at programming I guess.

---

No need to get discouraged over a simple problem. Just keep reading, trying things, debugging, reading some more, and if you still can't get it, come back here and ask questions. What about asking your teacher and/or classmates for help?

Offtopic: Why does it seem like all the other highschools in the world offer programming courses, and not mine? :(

I looked at your code more closely (that is, I actually put it in my compiler) and it looks like you've got a ton a little syntax errors. For example, you're missing a couple semicolons, and you type the wrong variable name ("newfile" is different than "newFile"). I'd say you need to write smaller portions of code between compiles.

Quote:

---

Originally Posted by JaWiB

Code:

---

bool getEmp(ifstream& empFile, string& lastName, string& firstName,
            double& salary, double& raise);
           
void writeEmp(ofstream& newFile, string& firstName, string&lastName,
              double& updatedSalary);

void calcSalary(double salary, double raise, double updatedSalary);

using namespace std;

---

ifstream, ofstream, and string are all part of the std namespace, so the compiler doesn't see them until after your using declaration. the simple fix is to put 'using namespace std' immediately after your includes.

>I pretty much suck at programming I guess.

Maybe, but I doubt you've been at it long enough to know that ;)

---

Thanks so much! You gave me the insight I needed to get this working.

Hmm, one more thing if anyone can figure this out. (I've been trying the past 30 minutes.) When my data is outputted, the updated salary is wrong. The output text file shows as:

Andrew Miller 1.8e-043
Sheila Green 1.8e-043
Amit Sethi 1.8e-043


Obviously, these salaries are wrong. Right now I'm just looking over my math and whatnot to see if I can figure this out, but if you have ideas let me know. Updated coded is below.

Code:

---

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

using namespace std;

bool getEmp (ifstream& empFile, string& lastName, string& firstName,
            float& salary, float& raise);
           
void writeEmp (ofstream& newFile, string& firstName, string&lastName,
              float& updatedSalary);

void calcSalary (float salary, float raise, float updatedSalary);



int main()
 { 
    cout << "Beginning employee salary updation.\n";           
    ifstream empFile ("Ch3_Ex8Data.txt");
    if (!empFile) {
    cerr << "The system was unable to open the file."; //error if file is in use.
    exit(100);  //if it is, terminate.
    }
    ofstream newFile ("Ch3_Ex8Output.dat");
    if (!newFile) {
    cerr << "They system was unable to open the file.";
    exit (102);
    }
   
 string firstName, lastName;
 float salary, raise, updatedSalary;
 
 while (getEmp  (empFile, lastName, firstName, salary, raise))
 {
      calcSalary (salary, raise, updatedSalary);
      writeEmp (newFile,  firstName, lastName, updatedSalary);
      } //end of while
     
 empFile.close();
 newFile.close();
 cout << "End of salary updation.\n";
 
 cout << salary;
return 0;

} //end of main


bool getEmp(ifstream& empFile, string& lastName, string& firstName,
            float& salary, float& raise)
{         
            empFile >> lastName >> firstName >> salary >> raise;
            if (!empFile)
              return false;
            return true;
} //end getEmp

void calcSalary(float salary, float raise, float updatedSalary)
{
      updatedSalary = (salary * (1+ (raise/100)));
   
    return;
} //end calcSalary

void writeEmp(ofstream& newFile, string& firstName, string& lastName,
              float& updatedSalary)
{
              newFile << setprecision(2) << firstName << "\t";
              newFile << lastName << "\t";
              newFile << updatedSalary << "\n";
              return;
} //end writeEmp

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edit i changed the setprecision line to this

Code:

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newFile << fixed << setprecision(2) << firstName << "\t";

---

Now sci-notation is gone, but the numbers are still wrong.

Code:

---

void calcSalary(float salary, float raise, float updatedSalary)
{
      updatedSalary = (salary * (1+ (raise/100)));
   
    return;
} //end calcSalary

---

The reason is, updatedSalary is local to this function. You probably forgot to pass it as a reference.
Although it would make more sense if the function took two float arguments and returned the result as float (not void return type).

Quote:

---

Originally Posted by JaWiB

ifstream, ofstream, and string are all part of the std namespace, so the compiler doesn't see them until after your using declaration. the simple fix is to put 'using namespace std' immediately after your includes.

---

The better fix (although not as simple) is to change all the ofstream to std::ofstream, string to std::string, etc.

In the end, "using namespace std;" really is a bad habit to get into. When you work on code seriously, those namespaces become a real benefit. I haven't used the keyword "using" for any reason for the past seven years; it actually makes code far more readable to keep the std:: everywhere (along with boost::, text::, and all the other namespaces I have).

On beginner code, it may make things easier, but it also tends to ingrain a bad habit you'll need to shake eventually.