bool empty() const for ranges

[Salih Dincer via Digitalmars-d-learn]

Hi All;

I have two questions that make each other redundant. Please 
answer one of them. I'm implementing ```bool empty() const``` for 
ranges as below:

```d
  bool empty() // const
  {
    bool result;

    if(!head)
    {
      result = true;
      fastRewind();
    }
    return result; // head ? false : true;
  }
```
* Is the const essential for ranges?
* Is it possible to rewind the pointer (```Node * head;```) when 
my head is empty by the const?

Thanks...