Iterate through array to make calculations using function pointers

funcptr.c

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

#define N_ELEMENTS(array) (sizeof(array)/sizeof(*array))
#define APPLY_FORMULA(result, array, func)\
   if (N_ELEMENTS(array)) {\
      result = array[0];\
      for (int8_t i = 1; i < N_ELEMENTS(array); i++)\
         result = func(result, array[i]);\
   } else\
      result = 0;

typedef uint16_t (*Formula_type)(uint16_t last, uint8_t nextItem);

static uint16_t add(uint16_t last, uint8_t nextItem)
{
   return last + nextItem;
}

static uint16_t mul(uint16_t last, uint8_t nextItem)
{
   return last * nextItem;
}

int main(void)
{
   uint8_t items[] =   { 1, 2, 3, 4 };
   uint16_t total_add;
   uint16_t total_mul;

   APPLY_FORMULA(total_add, items, add);
   APPLY_FORMULA(total_mul, items, mul);

   printf("Total from adding      = %d\n"
          "Total from multiplying = %d\n", total_add, total_mul);

   return EXIT_SUCCESS;
}