List Iterator Public Interface

bool      operator == (const iterator& I2) const;
bool      operator != (const iterator& I2) const;
iterator& operator =  (const iterator& I);
T&        operator *  ();         // Return reference to current Tval
const T&  operator *  () const;   // const version
iterator& operator ++ ();         // prefix
iterator  operator ++ (int);      // postfix
iterator& operator -- ();         // prefix
iterator  operator -- (int);      // postfix
bool      Valid       () const;   // Iterator is (pointing to) a valid element

• All iterator operations are required to run in time O(1) and space O(1).