/*
 * Copyright (C) 1998, 2000-2007, 2010, 2011, 2012, 2013 SINTEF ICT,
 * Applied Mathematics, Norway.
 *
 * Contact information: E-mail: tor.dokken@sintef.no                      
 * SINTEF ICT, Department of Applied Mathematics,                         
 * P.O. Box 124 Blindern,                                                 
 * 0314 Oslo, Norway.                                                     
 *
 * This file is part of TTL.
 *
 * TTL is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version. 
 *
 * TTL is distributed in the hope that it will be useful,        
 * but WITHOUT ANY WARRANTY; without even the implied warranty of         
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the          
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with TTL. If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public
 * License, a covered work must retain the producer line in every data
 * file that is created or manipulated using TTL.
 *
 * Other Usage
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the TTL library without
 * disclosing the source code of your own applications.
 *
 * This file may be used in accordance with the terms contained in a
 * written agreement between you and SINTEF ICT. 
 */

#ifndef _TTL_UTIL_H_
#define _TTL_UTIL_H_


#include <vector>
#include <algorithm>


#ifdef _MSC_VER
#  if _MSC_VER < 1300
#    include <minmax.h>
#  endif
#endif


//using namespace std;


/** \brief Utilities
*
*   This name space contains utility functions for TTL.\n
*
*   Point and vector algebra such as scalar product and cross product
*   between vectors are implemented here.
*   These functions are required by functions in the \ref ttl namespace,
*   where they are assumed to be present in the \ref hed::TTLtraits "TTLtraits" class.
*   Thus, the user can call these functions from the traits class.
*   For efficiency reasons, the user may consider implementing these
*   functions in the the API directly on the actual data structure;
*   see \ref api.
*
*   \note
*   - Cross product between vectors in the xy-plane delivers a scalar,
*     which is the z-component of the actual cross product
*     (the x and y components are both zero).
*
*   \see
*   ttl and \ref api
*
*   \author
*   Øyvind Hjelle, oyvindhj@ifi.uio.no
*/


namespace ttl_util {


  //------------------------------------------------------------------------------------------------
  // ------------------------------ Computational Geometry Group ----------------------------------
  //------------------------------------------------------------------------------------------------

  /** @name Computational geometry */
  //@{

  //------------------------------------------------------------------------------------------------
  /** Scalar product between two 2D vectors.
  *
  *   \par Returns:
  *   \code 
  *   dx1*dx2 + dy1*dy2
  *   \endcode
  */
  template <class real_type>
    real_type scalarProduct2d(real_type dx1, real_type dy1, real_type dx2, real_type dy2) {
    return dx1*dx2 + dy1*dy2;
  }


  //------------------------------------------------------------------------------------------------
  /** Cross product between two 2D vectors. (The z-component of the actual cross product.)
  *
  *   \par Returns:
  *   \code 
  *   dx1*dy2 - dy1*dx2
  *   \endcode
  */
  template <class real_type>
    real_type crossProduct2d(real_type dx1, real_type dy1, real_type dx2, real_type dy2) {
    return dx1*dy2 - dy1*dx2;
  }


  //------------------------------------------------------------------------------------------------
  /** Returns a positive value if the 2D nodes/points \e pa, \e pb, and
  *   \e pc occur in counterclockwise order; a negative value if they occur
  *   in clockwise order; and zero if they are collinear.
  *
  *   \note
  *   - This is a finite arithmetic fast version. It can be made more robust using
  *     exact arithmetic schemes by Jonathan Richard Shewchuk. See
  *     http://www-2.cs.cmu.edu/~quake/robust.html
  */
  template <class real_type>
    real_type orient2dfast(real_type pa[2], real_type pb[2], real_type pc[2]) {
    real_type acx = pa[0] - pc[0];
    real_type bcx = pb[0] - pc[0];
    real_type acy = pa[1] - pc[1];
    real_type bcy = pb[1] - pc[1];
    return acx * bcy - acy * bcx;
  }

}; // End of ttl_util namespace scope

#endif // _TTL_UTIL_H_
