/* $Id$
 *
 * Name:    exprBound.hpp
 * Author:  Pietro Belotti
 * Purpose: definition of the class for variable bounds 
 *
 * (C) Carnegie-Mellon University, 2006. 
 * This file is licensed under the Eclipse Public License (EPL)
 */

#ifndef COUENNE_EXPRBOUND_HPP
#define COUENNE_EXPRBOUND_HPP

#include <iostream>
#include <assert.h>

#include "CouenneTypes.hpp"
#include "CouenneExprVar.hpp"

namespace Couenne {

/// These are bound expression classes. They are used in the parametric
/// convexification part to obtain lower/upper bounds of an expression
/// as a function of the expression itself.
///
/// For example, the lower and upper bounds to expression (x1 - exp
/// (x2)) are (l1 - exp (u2)) and (u1 - exp (l2)), respectively, where
/// l1 (l2) is the lower bound of x1 (x2) and u1 (u2) is the upper
/// bound of x1 (x2).
///
/// A lower/upper bound of an expression is a function of all bounds in
/// the expression and is known only when all variables bounds are
/// known.


/// lower bound 

class COUENNELIB_EXPORT exprLowerBound: public exprVar {

 public:

  /// Node type
  inline enum nodeType Type () const
  {return CONST;}

  /// Constructor
  exprLowerBound (int varIndex, Domain *d = NULL):
    exprVar (varIndex, d) {}

  /// Copy constructor
  exprLowerBound (const exprLowerBound &src, Domain *d = NULL): 
    exprVar (src, d) {}

  /// cloning method
  inline exprLowerBound *clone (Domain *d = NULL) const
  {return new exprLowerBound (*this, d);}

  /// Print to iostream
  void print (std::ostream &out = std::cout, 
	      bool = false) const
  {out << "l_" << varIndex_;}

  /// return the value of the variable
  inline CouNumber operator () () 
  {assert (domain_); return domain_ -> lb (varIndex_);}

  /// differentiation
  inline expression *differentiate (int) 
  {return new exprConst (0.);}

  /// dependence on variable set
  inline int dependsOn (int *, int, enum dig_type type = STOP_AT_AUX) 
  {return 0;}

  /// get a measure of "how linear" the expression is:
  virtual inline int Linearity () 
  {return CONST;}

  /// code for comparisons
  virtual inline enum expr_type code ()
  {return COU_EXPRLBOUND;}
};


/// upper bound 

class COUENNELIB_EXPORT exprUpperBound: public exprVar {

 public:

  /// Node type
  inline enum nodeType Type () const
  {return CONST;}

  /// Constructor
  exprUpperBound (int varIndex, Domain *d = NULL):
    exprVar (varIndex, d) {}

  /// Copy constructor
  exprUpperBound (const exprUpperBound &src, Domain *d = NULL): 
    exprVar (src, d) {}

  /// cloning method
  inline exprUpperBound *clone (Domain *d = NULL) const
  {return new exprUpperBound (*this, d);}

  /// Print to iostream
  void print (std::ostream &out = std::cout, 
	      bool = false) const
  {out << "u_" << varIndex_;}

  /// return the value of the variable
  inline CouNumber operator () () 
  {assert (domain_); return domain_ -> ub (varIndex_);}

  /// differentiation
  inline expression *differentiate (int) 
  {return new exprConst (0.);}

  /// dependence on variable set
  inline int dependsOn (int *, int, enum dig_type type = STOP_AT_AUX) 
  {return 0;}

  /// get a measure of "how linear" the expression is:
  virtual inline int Linearity () 
  {return CONST;}

  /// code for comparisons
  virtual inline enum expr_type code ()
  {return COU_EXPRUBOUND;}
};

}

#endif