Thread: Having a problem with a struct.

Source

Code:

#include <stdio.h>


int fill_array(void);
int display_array(int count);


typedef struct
{
    char worker_name[20];
    float  hourly_pay;
    int  hours;
}WorkerRecord;


int main()
{
    WorkerRecord info[50];
    int count, k;
    float average_wage;
    
    count = fill_array();
    display_array(count);
    
    for(k = 0, average_wage = 0; k < count; k++)
    {
        average_wage += info[k].hourly_pay;
    }
    
    average_wage /= count;
    
    printf("\nAverage Hourly Wage: $%.2f", average_wage);


    printf("\n\nPress any key to continue...");
    getchar();
    return 0;
}


int fill_array(void)
{
    WorkerRecord info[50];
    int count = 0;
    
    FILE * pointer;
    
    pointer = fopen("workers.txt", "r");
    
    if(pointer == NULL)
    {
        printf("The file can not be found.\n\n\n");
        printf("Press any key to continue...");
        getch();
        return 1;
    }
    
    while(!feof(pointer))
    {
        fscanf(pointer, "%s%d%f", info[count].worker_name, &info[count].hours, &info[count].hourly_pay);
        count++;
    }


    fclose(pointer);
    
    return (count);
}


int display_array(int count)
{
    WorkerRecord info[50];
    int k;
    float gross_pay[50];
    
    
    printf(" Name\t\tHours\t\tHourly Pay\tGross Pay\n");
    printf("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
    
    for(k = 0; k < count; k++)
    {
        gross_pay[k] = (info[k].hourly_pay * info[k].hours);
    }
    
    for(k = 0; k < count; k++)
    {
        printf("%s\t\t%d\t\t$%.2f\t\t$%.2f\n", info[k].worker_name, info[k].hours, info[k].hourly_pay, gross_pay[k]);
    }
    
    return 0;
}

Workers.txt

Code:

Bob    40    10
Sean    35    12
Linda    30    15
Michael    45    9
Kelly    25    11

The area I am having trouble with, is in the main function when I am trying to compute/print the average hourly wage. For some reason, I am not getting the values from the struct correctly, even when i had no problems with my other two functions.

Thanks in advance,
Alan

Originally Posted by CommonTater

You are using average_wage without initializeing it's value.

I noticed, and changed, that in line 25 didn't I? (It might have been after you read it and before you posted this).

Originally Posted by CommonTater

Also for your functions... remove the struct definition and pass in a pointer to the array in main.

I am not sure what you mean here, I still only have limited knowledge on nearly everything more complex than the basics, which was what my class covers.
~~~~~
EDIT: Also, I am having a problem when I transfer my code from Geany to MSVC++.

<http://imgur.com/a/u5kRj>

The one that isn't full of random characters is from Geany.

Originally Posted by CommonTater

Then you need to do some serious reading on functions and pointers... Essentially, what happens inside a function stays inside the function and is destroyed when the function returns...

Ok, well I knew that much then, I just didn't know the technical way of saying it. I guess my problem is not understanding how structs fit into that. Why is it that I can use fill_array to store data in the struct, and display_array to display it, but can't use it in my main function? I did the exact same thing in my main function as I did my display_array function, so they should have the same effect, right?

And what did it print out for you?

You are getting the wrong values because it's working from random junk in the copy of info[50] in main.
C does not initialize arrays to 0... whatever random values are in memory where an array is created will be what you get.

Try it like this...

Code:

#include <stdio.h>


int fill_array(void);
int display_array(int count);


typedef struct
{
    char worker_name[20];
    float  hourly_pay;
    int  hours;
}WorkerRecord;


int main()
{
    WorkerRecord info[50];
    int count, k;
    float average_wage;
    
    count = fill_array(info, 50);
    display_array(info, count);
    
    for(k = 0, average_wage = 0; k < count; k++)
    {
        average_wage += info[k].hourly_pay;
    }
    
    average_wage /= count;
    
    printf("\nAverage Hourly Wage: $%.2f", average_wage);


    printf("\n\nPress any key to continue...");
    getchar();
    return 0;
}


int fill_array(int *arr, int max)
{
    int count = 0;
    
    FILE * pointer;
    
    pointer = fopen("workers.txt", "r");
    
    if(pointer == NULL)
    {
        printf("The file can not be found.\n\n\n");
        printf("Press any key to continue...");
        getch();
        exit(1);
    }
    
    while {fscanf(pointer, "%s%d%f", arr[count]->worker_name, &arr[count]->hours, &arr[count]->hourly_pay) > 2)   
       {
        count++;
        if (count >= max)
          break;
       }
    fclose(pointer);
    
    return (count);
}


int display_array(int *arr, int count)
{
     int k;
     float grosspay[50];    
    
    printf(" Name\t\tHours\t\tHourly Pay\tGross Pay\n");
    printf("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
    
    for(k = 0; k < count; k++)
    {
        gross_pay[k] = (arr[k]->hourly_pay * arr[k]->hours);
    }
    
    for(k = 0; k < count; k++)
    {
        printf("%s\t\t%d\t\t$%.2f\t\t$%.2f\n", arr[k]->worker_name, arr[k]->hours, arr[k]->hourly_pay, gross_pay[k]);
    }
    
    return 0;
}

Originally Posted by CommonTater

And what did it print out for you?

You are getting the wrong values because it's working from random junk in the copy of info[50] in main.
C does not initialize arrays to 0... whatever random values are in memory where an array is created will be what you get.

In display_array, everything got printed correctly (see the first image in this link <Photo Album - Imgur>), which is why I am having trouble understanding what I need to do differently.

EDIT:

Code:

gross_pay[k] = (arr[k]->hourly_pay * arr[k]->hours);

Now I am severely confused. Not only am I not understanding where arr is coming from, but I've never seen "->" used in code as of yet. And furthermore, will that change anything in my main function? The only problem I was having from the getgo was computing the average hourly wage in the main function. But, when you mentioned that I kept making new arrays in each function, I was wondering why my display_array function worked even though my only input was the count.