average.c

#include <stdio.h>
#include <stdlib.h>

#include "array.h"

#define INT_TO_PTR(x) ((void *) (size_t) (x))
#define PTR_TO_INT(x) ((int) (size_t) (x))

static double
total_val (const Array *array,
           ValueFunc    func)
{
    double total = 0;
    size_t length = array_get_length (array);

    for (size_t i = 0; i < length; i++)
        total += func (array_get (array, i));

    return total;
}

static double
average_val (const Array *array,
             ValueFunc    func)
{
    return total_val (array, func) / array_get_length (array);
}

static double
array_to_int (const void *data)
{
    return (double) PTR_TO_INT (data);
}

static void
print_array (Array *array)
{
    size_t length = array_get_length (array);
    printf ("Array at %p is of length %zu\n", array, length);
    printf ("Array has capacity %zu\n", array_get_capacity (array));

    double total = total_val (array, array_to_int);
    double average = average_val (array, array_to_int);
    
    printf ("Array total is %lf\n", total);
    printf ("Array average is %lf\n", average);
}

static Array *
create_test_array (size_t start,
                   size_t end)
{
    Array *array = array_new (NULL);

    for (size_t i = start; i < end; i++)
        array_add (array, INT_TO_PTR (i));

    return array;
}

int
main (void)
{
    Array *array = create_test_array (0, 100);
    print_array (array);

    return EXIT_SUCCESS;
}