Pointer Arithmetic

pointer_arithmetic.c

int main() 
{

/* ====================================================================== */
    /* Pointer Arithmetic */
    /* ====================================================================== */
    /*
        int urn[3];
        int *ptr1, *ptr2

        Valid:
        - ptr1++;
        - ptr2 = ptr1 + 2;
        - ptr2 = urn + 1;

        Invalid:
        - urn++;
        - ptr2 = ptr2 + ptr1;
        - ptr2 = urn * ptr1;
    */
    int arraySum(int arrat[], const int sizeOfArray);
    int arraySumTwo(int arrat[], const int sizeOfArray);

    char charArr[4] = {'a', 'b', 'c'};
    char *charPtr = charArr;

    printf("charPtr #0 = %c\n", *charPtr); // a
    printf("charPtr #1 = %c\n", *(charPtr + 1)); // b
    printf("charPtr #2 = %c\n\n", *(charPtr + 2)); // c

    // set values
    *charPtr = 'd';
    *(charPtr + 1) = 'e';
    *(charPtr + 2) = 'f';
    printf(
           "charPtr #0 = %c\n"
           "charPtr #1 = %c\n"
           "charPtr #2 = %c\n",
           *charPtr, *(charPtr + 1), *(charPtr + 2) // d, e, f
           );



    int values[10] = {3, 7, -9, 3, 6, -1, 7, 9, 1, -5};

    int result = arraySumTwo(values, 10);

    printf("The sum is %i\n", result);


    return 0;
}

/** Adds all items of array together*/
int arraySum(int array[], const int sizeOfArray)
{
    int sum = 0, *ptr;
    // Cannot change what arrayEnd points to - const is more efficient for the compiler
    int *const arrayEnd = array + sizeOfArray; // &arr + 10 = address of end of array
    // ptr is a hexadecimal address
    for (ptr = array; ptr < arrayEnd; ++ptr)
        sum += *ptr; // dereference ptr's each item in the array value

    return sum;
}

/**
 * Adds all items of array together
 * Cut down version, using a pointer to array syntax
 */
int arraySumTwo(int *array, const int sizeOfArray)
{
    int sum = 0;
    // Cannot change what arrayEnd points to - const is more efficient for the compiler
    int *const arrayEnd = array + sizeOfArray; // &arr + 10 = address of end of array
    // ptr is a hexadecimal address
    for (; array < arrayEnd; ++array)
        sum += *array; // dereference ptr's each item in the array value

    return sum;
}