// --------------------------------------------------------------------------
// Linear Containers
// A. Fischer June 12, 2001                                  file: linear.hpp
// --------------------------------------------------------------------------
#pragma once

#include <iostream>
#include "container.hpp"
#include "cell.hpp"
#include "item.hpp"
using namespace std;

class Linear: public Container {
  protected: // -------------------------------------------------------------
    Cell* head;      // This is a dummy header for the list.

  private:   // -------------------------------------------------------------
    Cell* here;      // Cursor for traversing the container.
    Cell* prior;     // Trailing pointer for traversing the container.

  protected: // -------------------------------------------------------------
            Linear(): head(new Cell), here( NULL ), prior( head ) {}
    virtual ~Linear ();
            void  reset()           { prior = head; here = head->next; }
            bool  end() const       { return here == NULL; }
            void  operator ++();

    virtual void  insert( Cell* cp );
    virtual void  focus() = 0;
            Cell* remove();
            void  setPrior(Cell* cp){ prior = cp; here = prior->next; }
    bool    operator<  ( Cell* cp ) { return (*cp->data < *here->data); }
    bool    operator<  ( KeyType k ){ return *here->data < k; }
    bool    operator== ( KeyType k ){ return *here->data == k; }

  public:   // --------------------------------------------------------------
            void     put(Item * ep) { if (ep) insert( new Cell(ep) ); }
            Item*    pop();
            Item*    peek()         { focus(); return *here; }
    virtual ostream& print( ostream& out );
};
inline ostream& operator<<(ostream& out, Linear& s) {return s.print(out); }