#ifndef _CREF_H_
#define _CREF_H_

#include <stdlib.h>

class NullPointerException {};

/**
 * Class that wraps a constant reference variable.
 * Useful for return value from a container find method.
 */
template <class Object>
class Cref
{
  public:
    Cref( ) : obj( NULL ) { }
    explicit Cref( const Object & x ) : obj( &x ) { }

    const Object & get( ) const
      { if( isNull( ) ) throw NullPointerException( ); else return *obj; }
    bool isNull( ) const
      { return obj == NULL; }

  private:
    const Object *obj;
};

#endif