Why can we use function pointers both as (*func_ptr)() and func_ptr() to invoke a function,but not so for array pointers?

Question

Suppose we have a function pointer func_ptr of type void (*func_ptr)().Then we know that using this we can invoke the function using this pointer both as :

    (*func_ptr)();
    func_ptr();

But again, suppose we have a pointer to an integer array int (*arr_ptr)[5], then why can't we refer to the array as arr_ptr[], and consequently its elements as arr_ptr[0],arr_ptr[1] etc? Why can we only use (*arr_ptr)[0] and (*arr_ptr)[1]?

Answer 1

The type of arr_ptr[0] is int [5]; the type of (*arr_ptr)[0] is int. If you wanted to, you could use arr_ptr[0][0].

#include <stdio.h>

int main(void) {
  int (*arr_ptr)[5];
  int a[2][5] = {{1, 2, 3, 4, 5}, {11, 12, 13, 14, 15}};
  arr_ptr = a;
  printf("%d %d\n", (*arr_ptr)[2], arr_ptr[1][2]);
  return 0;
}

You can see the code "running" at ideone.

That a function pointer can be used either way is just (nice) sintactic sugar.