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/* This file is part of the Gudhi Library. The Gudhi library
* (Geometric Understanding in Higher Dimensions) is a generic C++
* library for computational topology.
*
* Author(s): Clément Maria
*
* Copyright (C) 2014 Inria
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef DISTANCE_FUNCTIONS_H_
#define DISTANCE_FUNCTIONS_H_
#include <gudhi/Debug_utils.h>
#include <gudhi/Miniball.hpp>
#include <boost/range/metafunctions.hpp>
#include <boost/range/size.hpp>
#include <cmath> // for std::sqrt
#include <type_traits> // for std::decay
#include <iterator> // for std::begin, std::end
#include <utility>
namespace Gudhi {
/** @file
* @brief Global distance functions
*/
/** @brief Compute the Euclidean distance between two Points given by a range of coordinates. The points are assumed to
* have the same dimension. */
class Euclidean_distance {
public:
// boost::range_value is not SFINAE-friendly so we cannot use it in the return type
template< typename Point >
typename std::iterator_traits<typename boost::range_iterator<Point>::type>::value_type
operator()(const Point& p1, const Point& p2) const {
auto it1 = std::begin(p1);
auto it2 = std::begin(p2);
typedef typename boost::range_value<Point>::type NT;
NT dist = 0;
for (; it1 != std::end(p1); ++it1, ++it2) {
GUDHI_CHECK(it2 != std::end(p2), "inconsistent point dimensions");
NT tmp = *it1 - *it2;
dist += tmp*tmp;
}
GUDHI_CHECK(it2 == std::end(p2), "inconsistent point dimensions");
using std::sqrt;
return sqrt(dist);
}
template< typename T >
T operator() (const std::pair< T, T >& f, const std::pair< T, T >& s) const {
T dx = f.first - s.first;
T dy = f.second - s.second;
using std::sqrt;
return sqrt(dx*dx + dy*dy);
}
};
/** @brief Compute the radius of the minimal enclosing ball between Points given by a range of coordinates.
* The points are assumed to have the same dimension. */
class Minimal_enclosing_ball_radius {
public:
/** \brief Minimal_enclosing_ball_radius from two points.
*
* @param[in] point_1 First point.
* @param[in] point_2 second point.
* @return The minimal enclosing ball radius for the two points (aka. Euclidean distance / 2.).
*
* \tparam Point must be a range of Cartesian coordinates.
*
*/
template< typename Point >
typename std::iterator_traits<typename boost::range_iterator<Point>::type>::value_type
operator()(const Point& point_1, const Point& point_2) const {
return Euclidean_distance()(point_1, point_2) / 2.;
}
/** \brief Minimal_enclosing_ball_radius from a point cloud.
*
* @param[in] point_cloud The points.
* @return The minimal enclosing ball radius for the points.
*
* \tparam Point_cloud must be a range of points with Cartesian coordinates.
* Point_cloud is a range over a range of Coordinate.
*
*/
template< typename Point_cloud,
typename Point_iterator = typename boost::range_const_iterator<Point_cloud>::type,
typename Point = typename std::iterator_traits<Point_iterator>::value_type,
typename Coordinate_iterator = typename boost::range_const_iterator<Point>::type,
typename Coordinate = typename std::iterator_traits<Coordinate_iterator>::value_type>
Coordinate
operator()(const Point_cloud& point_cloud) const {
using Min_sphere = Miniball::Miniball<Miniball::CoordAccessor<Point_iterator, Coordinate_iterator>>;
Min_sphere ms(boost::size(*point_cloud.begin()), point_cloud.begin(), point_cloud.end());
#ifdef DEBUG_TRACES
std::cout << "Minimal_enclosing_ball_radius = " << std::sqrt(ms.squared_radius()) << " | nb points = "
<< boost::size(point_cloud) << " | dimension = "
<< boost::size(*point_cloud.begin()) << std::endl;
#endif // DEBUG_TRACES
return std::sqrt(ms.squared_radius());
}
};
} // namespace Gudhi
#endif // DISTANCE_FUNCTIONS_H_
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