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#ifndef __EST_TDEQUE_H__
#define __EST_TDEQUE_H__

#include "EST_TVector.h"
#include "instantiate/EST_TDequeI.h"

/** Double ended queue.
  * 
  * @author Richard Caley <rjc@cstr.ed.ac.uk>
  * @version $Id: EST_TDeque.h,v 1.2 2001/04/04 13:11:27 awb Exp $
  */

template <class T>
class EST_TDeque {
private:
  EST_TVector<T> p_vector;
  int p_increment;
  int p_back;
  int p_front;

  // Make the structure bigger.
  void expand(void);

public:
  EST_TDeque(unsigned int capacity, unsigned int increment);
  EST_TDeque(unsigned int capacity);
  EST_TDeque(void);

  /// Used to fill empty spaces when possible.
  static const T *Filler;

  /// Empty it out.
  void clear(void);

  /// Is there anything to get?
  bool is_empty(void) const;

  /// print picture of state. Mostly useful for debugging.
  ostream &print(ostream &s) const;

  /**@name stack
    * 
    * An interface looking like a stack.
    */
  //@{
  void push(T &item);
  T &pop(void);
  T &nth(int i);
  //@}

  /**@name inverse stack
    * 
    * The other end as a stack.
    */
  //@{
  void back_push(T& item);
  T &back_pop(void);
  //@}

  /**@name queue
    * 
    * An interface looking like a queue.
    */
  //@{
  void add(T& item) { push(item); }
  T &next() { return back_pop(); }
  T &last() { return pop(); }
  //@}

  /**@name perl
    * 
    * For people who think in perl
    */
  //@{
  void unshift(T& item) { back_push(item); }
  T &shift() { return back_pop(); }
  //@}

  friend ostream& operator << (ostream &st, const EST_TDeque< T > &deq);
};

template<class T> 
extern ostream& operator << (ostream &st, const EST_TDeque< T > &deq);

#endif

