observer.h  From Astrachan, p. 326
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#ifndef _OBSERVER_H
#define _OBSERVER_H

// a class for observing a one-dimensional random walk
// this version records the events of the walk in
// a text file whose name is specified in a parameter to
// the constructor
//
// WalkObserver(const string & filename)-- observer records output
//                                         in the text file "filename"
//
// void Update(int step, int position) --  called by a walking object
//                                         to observe (record) the walk

class WalkObserver
{
  public:
    
    WalkObserver(const string & filename);  // specify filename
    void Update(int step, int position);    // update information from walker
    
  private:
    
    ofstream myOutputStream;                // output stream for data
};

#endif