/*
** $Id: counter,v 1.1 2003/01/21 05:59:00 phf Exp $
**
** Copyright (c) 2003 by Peter H. Froehlich <phf@acm.org>.
** Freely distributable for educational purposes.
*/

#ifndef _CS14_COUNTER
#define _CS14_COUNTER

#include <stdexcept>

namespace cs14 {

/*
** Interface class for ADT Counter.
**
** Counters have an integer value and can be restricted to a
** certain range.
*/

class Counter {
public:
  /*
  ** Constructor.
  **
  ** Create new counters according to the ADT specification.
  **
  ** new: Integer x Integer -/-> Counter
  **   lower and upper as given, lower <= upper must hold,
  **   new counter starts at 0 (i.e. get( new() ) == 0).
  ** 
  ** We cannot declare the constructor here, it must be added
  ** in each implementation class.
  */

  /*
  ** Observers.
  **
  ** lower: Counter ---> Integer
  **   lower bound
  ** upper: Counter ---> Integer
  **   upper bound
  ** get: Counter ---> Integer
  **   current value
  */
  virtual int lower() const =0;
  virtual int upper() const =0;
  virtual int get() const =0;

  /*
  ** Modifiers.
  **
  ** set: Counter x Integer -/-> Counter
  **   set current value, must be in range
  ** inc: Counter -/-> Counter
  **   increase current value, result must be in range,
  **   increase by 1 (i.e. get( inc( c ) ) == get(c)+1).
  ** dec: Counter -/-> Counter
  **   decrease current value, result must be in range,
  **   decrease by 1 (i.e. get( dec( c ) ) == get(c)-1).
  */
  virtual void set( int i ) throw (std::domain_error) =0;
  virtual void inc() throw (std::domain_error) =0;
  virtual void dec() throw (std::domain_error) =0;

  /*
  ** More idiomatic ways to express inc and dec. They can
  ** be implemented here since they just use the above.
  */
  virtual Counter& operator++() throw (std::domain_error) {
    inc(); return *this;
  }
  virtual Counter& operator--() throw (std::domain_error) {
    dec(); return *this;
  }

}; // Counter

} // namespace cs14

#endif /* _CS14_COUNTER */