Thread: Help finding average?

Ok, I realize I just asked for help, but I am so confused right now. I have been working for the past hour on another problem (which is just an add on to the last one I posted about), and I know I am SOMEWHERE on the right track, but I just need a tad bit of guidance? My professor didn't give me much to go off of to find the average using arrays/loops, except the following model function:

Code:

double find_average(int * array, int size)
{
   int sum = 0;
   int i;
   for(i = 0; i < size; i++) 
  { sum += array[i]; } /* running total */
  return sum/ sizeof(array)/sizeof(*array);
}

I need to find the average of all of the scores. This is what I have, and after is the errors I am getting.

Code:

# include <stdio.h>

/*prototypes*/
double find_average(double *score[], int size);

int main()
{
        double score[5];
        int i;
        double average;
        int size;

        size=5;
        score[0]= 81.4;
        score[1]= 75.3;
        score[2]= 90.0;
        score[3]= 96.9;
        score[4]= 85.6;

        printf( "The grades are:" );

        for (i=0; i < sizeof(score)/sizeof(*score); i++)
        {
                printf(" %.1lf", score[i]);
        }
        printf("\n");

        printf("The average is: ");
        average = find_average(*score, size);
        printf("/n");

        return 0;
}


/*methods*/
double find_average(double *score[], int size)
{
   int sum = 0;
 int i;
   for(i = 0; i < size; i++)
  { sum += score[i]; }
  return sum / (sizeof(score)/sizeof(*score));
}

Errors:
hw10test2.c: In function âmainâ:
hw10test2.c:29: error: incompatible type for argument 1 of âfind_averageâ
hw10test2.c:4: note: expected âdouble **â but argument is of type âdoubleâ
hw10test2.c: In function âfind_averageâ:
hw10test2.c:42: warning: assignment makes integer from pointer without a cast

Once again, any help would be greatly appreciated! I hate asking for help, but I just can't figure this out for some reason. I have almost nothing to go off of (no instruction related to this specifically, just some vague instructions on passing techniques).

Thank you!

Code:

double find_average(int * array, int size)
{
   int sum = 0;
   int i;
   for(i = 0; i < size; i++) 
  { sum += array[i]; } /* running total */
  return sum/ sizeof(array)/sizeof(*array);
}

You are passing in the size, what is up with this?

Code:

return sum/ sizeof(array)/sizeof(*array);

To pass a pointer to a type you use the address-of operator, &, not the dereference operator, *.

I am honestly not sure. I have only that model to go off of. In class, he said, "Oh, and here are a few models you can refer to later", and that was it. And, according to what was given, I thought that was what I was supposed to do? Is there any resource that could explain this a little more clearly? I honestly don't know what I am doing. The code you quoted is the model I was given. That is his work (the model), not mine. In my code, I was just trying to work with what I was given.

FYI: The reason you pass the size to the function is that sizeof() will NOT give you the correct size of the array.

Array names decay into pointers when passed to functions; pointers have a constant size not based on the number of items in the array.

Tim S.

Referring to your first code sample in message 1...

Line 7 should be...

Code:

return sum / size;

Thank you guys!!! You put me on the right track. I got it!

Code:

 
# include <stdio.h>

/*prototypes*/
double find_average(double *array, double size);

int main()
{
        double score[5];
        int i;
        double size;
        double average;

        size=5;
        score[0]= 81.4;
        score[1]= 75.3;
        score[2]= 90.0;
        score[3]= 96.9;
        score[4]= 85.6;

        printf( "The grades are:" );

        for (i=0; i < sizeof(score)/sizeof(*score); i++)
        {
                printf(" %.1lf", score[i]);
        }
        printf("\n");

        printf("The average is: ");
        average = find_average(score, size);
        printf("%.2lf", average);
        printf("\n");

        return 0;
}


/*methods*/
double find_average(double *array, double size)
{
   double sum = 0;
   int i;
   for(i = 0; i < size; i++)
  { sum += array[i]; }
  return sum / size;
}