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

int sum( int *nums, int array_len ) {
    int total = 0;
    for (int i = 0; i < array_len; i++) {
        total += nums[i];
    }
    return total;
}

// Demonstrate pointer arithmetic and accessing elements of arrays.
void array_demo1() {
    short i;
	int *x = (int *)malloc(sizeof(int) * 6); // 
	int a[6];
	
	printf( "x is pointing to %p\n", x );
	printf( "x is stored at %p\n", &x );
	printf( "a is stored at %p\n", &a );
    for (i = 0; i < 6; i++) {
        x[i] = i*10;
        a[i] = i*10;
    }

    // pointer arithmetic
    // a + 1 is bytes beyond a because a is a pointer to ints and ints
    // are 4 bytes. This is a little on the complicated side until you
    // look at it like this: a[i] is equivalent to *(a+i), which means
    // go i elements beyond the beginning of the array and dereference
    // it.
    for (i = 0; i < 6; i++) {
        printf( "a[i] is at %p = %p\n", &(a[i]), a+i );
    }
    for (i = 0; i < 6; i++) {
        printf( "x[i] is at %p = %p\n", &(x[i]), x+i );
    }
    
    int t1 = sum( a, 6 );
    int t2 = sum( x, 6 );
    printf( "Sum of a's = %d, sum of x's = %d\n", t1, t2 );

}

int main (int argc, char *argv[]) {
    array_demo1();
}