// ------------------------------------------------------------------------
// Ordered base class -- An abstract class
// A. Fischer  June 8, 1998                               file: ordered.hpp
//
#pragma once

#include <limits.h>
#include <iostream>
using namespace std;

// How should an ordered abstract class be defined?
//
// The primary interface defines an ordering relation between
// an element and a KeyType.
//
// The alternative interface defines an abstract ordering relation
// on elements of type "Ordered".  This appears to be more general,
// but it requires some means of obtaining the data to be used
// in defining the comparison operators; hence the key() function.
//
// To allow both interfaces to be explored, the symbol below
// selects which interface is to be used.
#define PRIMARY_INTERFACE

// ------------------------------------------------------------------------
template <class KeyType>
class Ordered {
  public:
    virtual ~Ordered(){}

    // Promises
#ifdef PRIMARY_INTERFACE
    virtual bool    operator <  (const KeyType&) const  =0;
    virtual bool    operator == (const KeyType&) const  =0;

#else
    // Alternative interface
    virtual KeyType key() const                         =0;
    virtual bool    operator <  (const Ordered&) const  =0;
    virtual bool    operator == (const Ordered&) const  =0;
#endif

};