Practice examples: arrays and pointers

Show the output from the following programs: 

  1. #include <iostream>
using namespace std;

// arr is a constant array - contents cannot be changed by f0
void f0(const int arr[])
{
   printf("f0\n");
   int a = 9;
   printf("Param addr:  %p Value: %d\n", arr, arr[0]);
   // arr[0]++;  // not allowed to change contents of a const array
   arr = &a;
   printf("After reset: %p Value: %d\n\n", arr, arr[0]);
}

// arr is a constant ptr - contents cannot be changed by f1
void f1(const int* arr)
{
   printf("f0\n");
   int a = 9;
   printf("Param addr:  %p Value: %d\n", arr, arr[0]);
   // arr[0]++;  // not allowed to change contents of a const array
   arr = &a;
   printf("After reset: %p Value: %d\n\n", arr, arr[0]);
}

// arr is a regular ptr - contents can be changed
void f2(int *arr)
{
   printf("f0\n");
   int a = 9;
   printf("Param addr:  %p Value: %d\n", arr, arr[0]);
   arr[0]++;
   arr = &a;
   printf("After reset: %p Value: %d\n\n", arr, arr[0]);
}

// arr is a regular array - contents can be changed
void f3(int arr[])
{
   printf("f0\n");
   int a = 9;
   printf("Param addr:  %p Value: %d\n", arr, arr[0]);
   arr[0]++;
   arr = &a;
   printf("After reset: %p Value: %d\n\n", arr, arr[0]);
}

// arr is a pointer passed by reference,
//     both the array contents AND the pointer itself
//     can be changed by the function
void f4(int* &arr)
{
   printf("f0\n");
   int a = 9;
   printf("Param addr:  %p Value: %d\n", arr, arr[0]);
   arr[0]++;
   arr = &a;
   printf("After reset: %p Value: %d\n\n", arr, arr[0]);
}

int main()
{
   int array[3] = { 0, 3, 6 };

   f0(array);
   f1(array);
   f2(array);
   f3(array);
   // f4(array);  // not allowed, can't pass an array by reference

   int *dynamicArray = new int[3];
   if (dynamicArray != NULL) {
      dynamicArray[0] = 0;
      f4(dynamicArray);
      printf("After f4:    %p\n", (dynamicArray));
   }
}