Implementing a function into into my program?

8100 Power · #1 11-Oct-2008, 00:47

Hi, I've wrote my grade averaging program. But, my teacher is asking us to use functions and have the function return the average instead of the cout. This is what I have so far:

CPP / C++ / C Code:

#include <iostream>
using namespace std;


int main(){
    
    int total=0;
    int gradeCounter=1;
    int grade, maxgrades;
    int average;


    cout << "How many Grades do you want to enter?" << endl;
    cin >> maxgrades;

    cout << "Enter " << maxgrades << " grades" << endl;

    while (gradeCounter <= maxgrades){
          cout << "Enter Grade: ";
          cin >> grade;
          total = total + grade;
          gradeCounter = gradeCounter + 1;
          average = total / maxgrades;
    }
    
    
    cout << "Average Grades: " << average << endl;
    
    
    system("PAUSE");
    return 0;
    
}

Functions is new to me, as well as C++.

ocicat · #2 11-Oct-2008, 01:19

Quote:

Originally Posted by 8100 Power

Hi, I've wrote my grade averaging program. But, my teacher is asking us to use functions and have the function return the average instead of the cout.

You haven't asked a question, but I assume that you are wanting assistance in creating a function. If this is correct, study the following example:

CPP / C++ / C Code:

#include <iostream>

using namespace std;

int f(int);

int main() {
    int i = 0, j = 1;

    cout << "i (main()) =  " << i << endl;
    cout << "j (main()) =  " << j << endl;

    i = f(j);

    cout << "i (main()) =  " << i << endl;
    cout << "j (main()) =  " << j << endl;

    return 0;
}

int f(int k) {
    int v = 0;

    cout << "\tk (f()) =  " << k << endl;
    cout << "\tv (f()) =  " << v << endl;

    v = ++k;

    cout << "\tk (f()) =  " << k << endl;
    cout << "\tv (f()) =  " << v << endl;

    return v;
}

Various comments:

Compile & execute this example. Study the output of execution & compare it to the source code to understand then intended behaviour.
Study the syntax. A function prototype is provided as well.
Recognize that main() is a function as well.

If you still have questions, ask specifically about what is still unclear.

8100 Power · #3 11-Oct-2008, 11:53

I guess what i'm saying is. I'm trying to implement all of my "math" into the function, and then call it in my main function. I've correctly called functions, but, I don't understand this one. I don't know what to call since I'm averaging all the grades and outputting the average.

8100 Power · #4 11-Oct-2008, 13:27

This is what I have. But, I have a continuous loop, it isn't stopping..

CPP / C++ / C Code:

#include <iostream>
using namespace std;

double gradeAvg(double);

int main(){
    
    int total=0;
    int gradeCounter=1;
    double grade; 
    int maxgrades;
    int average;


    cout << "How many Grades do you want to enter?" << endl;
    cin >> maxgrades;

    cout << "Enter " << maxgrades << " grades" << endl;

    while (gradeCounter <= maxgrades){
          cout << "Enter Grade: ";
          cin >> grade;
          double gradeAvg( average);
    }
    
    
    cout << "Average Grades: " << average << endl;
    
    
    system("PAUSE");
    return 0;
    
}

double gradeAvg ( double average){
  int total, gradeCounter, maxgrades;
  double grade;


    total = total + grade;
    gradeCounter = gradeCounter + 1;
    average = total / maxgrades;

    cout << "Average Grades: " << average << endl;

return average;
}

Howard_L · #5 11-Oct-2008, 17:03

CPP / C++ / C Code:

while (gradeCounter <= maxgrades)
  {
    /* Put a printf() and a getchar() inside of this loop to print the values 
     of all variables concerned.  Maybe a if(gradeCounter  > 50) break; too */
  }

dlp · #6 11-Oct-2008, 17:24

1. Why should gradeCounter ever become more than maxgrades? You never change the value.

2. I don't think your instructor is being clear about your requirements for the function. If you never call cout/cin in the function gradeAvg, you will only average one value unless you:
a) do fun math by making an average, then undoing the average and recalculating with another value.
b) Pass a bunch of numbers into gradeAvg function, which means you have to know how to use std::list or std::vector, which seems a bit above the scope of this program.

Either we or you need more details about your assignment to help you out.

8100 Power · #7 11-Oct-2008, 18:49

Quote:

Originally Posted by dlp

1. Why should gradeCounter ever become more than maxgrades? You never change the value.

2. I don't think your instructor is being clear about your requirements for the function. If you never call cout/cin in the function gradeAvg, you will only average one value unless you:
a) do fun math by making an average, then undoing the average and recalculating with another value.
b) Pass a bunch of numbers into gradeAvg function, which means you have to know how to use std::list or std::vector, which seems a bit above the scope of this program.

Either we or you need more details about your assignment to help you out.

1. That's my loop control variable.

2. I totally agree on the instructors assignment. She hasn't be clear since day one!

a) ?? Don't really understand.
b) We haven't learned that yet..

Instructions as I see it:
" Modify your get average program so that it returns the function rather than cout."

Howard_L · #8 11-Oct-2008, 19:48

Did you fix the loop yet? You need to have that working correctly first.

CPP / C++ / C Code:

    while (gradeCounter++ < maxgrades)
    {
        cout <<"gradeCounter= "<< gradeCounter <<"  maxgrades= "<< maxgrades << endl;

You may want to consider the versatility of a 'for' loop there.

Quote:

Modify your get average program so that it returns the function rather than cout.

You mean 'returns the average rather than printing it from the function' don't you?
Do you need to store the grades which the users inputs?
If so you'll need to assign them to an array or something as they are entered within the loop.

Regardless, you wouldn't call the average() function until you have:
- the total of all the values
- total number of input values
So take the function call out of the loop, and instead add up the values as they are input within the loop ,
and then call a slightly different function than you presently have (which is close)

CPP / C++ / C Code:

double average(double total, int num)

Don't forget you will need to catch that returned value in main() in order to print it from there...

ocicat · #9 11-Oct-2008, 22:39

Quote:

Originally Posted by 8100 Power

CPP / C++ / C Code:

double gradeAvg( average);

You are calling the function, but you are not retaining what its return value. Do so through something similar to the following:

CPP / C++ / C Code:

double value = grade(average);

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