/* $Id$
 *
 * Name:    exprAbs.hpp
 * Author:  Pietro Belotti
 * Purpose: definition of the absolute value of a function
 *
 * (C) Carnegie-Mellon University, 2006-10.
 * This file is licensed under the Eclipse Public License (EPL)
 */

#ifndef COUENNE_EXPRABS_HPP
#define COUENNE_EXPRABS_HPP

#include <math.h>

#include "CouenneExprUnary.hpp"
#include "CouenneExprConst.hpp"

namespace Couenne {

/// class for \f$ |f(x)| \f$

class COUENNELIB_EXPORT exprAbs: public exprUnary {

 public:

  /// Constructor
  exprAbs  (expression *al): 
    exprUnary (al) {} //< non-leaf expression, with argument list

  /// The operator's function
  inline unary_function F () {return fabs;}

  /// cloning method
  expression *clone (Domain *d = NULL) const
    {return new exprAbs (argument_ -> clone (d));}

  /// output
  std::string printOp () const
    {return "abs";}

  /// return l_2 norm of gradient at given point
  inline CouNumber gradientNorm (const double *x)
  {return ((argument_ -> Index () < 0) ? 0. : 1.);}

  /// differentiation
  expression *differentiate (int index); 

  /// Get lower and upper bound of an expression (if any)
  virtual void getBounds (expression *&, expression *&);

  /// Get value of lower and upper bound of an expression (if any)
  virtual void getBounds (CouNumber &lb, CouNumber &ub);

  /// generate equality between *this and *w
  void generateCuts (expression *w, //const OsiSolverInterface &si, 
		     OsiCuts &cs, const CouenneCutGenerator *cg, 
		     t_chg_bounds * = NULL, int = -1, 
		     CouNumber = -COUENNE_INFINITY, 
		     CouNumber =  COUENNE_INFINITY);

  /// code for comparisons
  enum expr_type code () {return COU_EXPRABS;}

  /// is this expression integer?
  inline bool isInteger ()
  {return argument_ -> isInteger ();}

  /// implied bound processing
  bool impliedBound (int, CouNumber *, CouNumber *, t_chg_bounds *, enum auxSign = expression::AUX_EQ);

  /// set up branching object by evaluating many branching points for
  /// each expression's arguments
  virtual CouNumber selectBranch (const CouenneObject *obj, 
				  const OsiBranchingInformation *info,
				  expression * &var, 
				  double * &brpts, 
 				  double * &brDist, // distance of current LP
					  	    // point to new convexifications
				  int &way);

  /// closest feasible points in function in both directions
  virtual void closestFeasible (expression *varind, expression *vardep,
				CouNumber& left, CouNumber& right) const;

  /// can this expression be further linearized or are we on its
  /// concave ("bad") side
  virtual bool isCuttable (CouenneProblem *problem, int index) const;

  /// either CONVEX, CONCAVE, AFFINE, or NONCONVEX
  //virtual enum convexity convexity () const;
};

}

#endif