1 files changed, 78 insertions, 0 deletions
diff --git a/src/Cech_complex/include/gudhi/Sphere_circumradius.h b/src/Cech_complex/include/gudhi/Sphere_circumradius.h
new file mode 100644
index 00000000..2f916c0a
--- /dev/null
+++ b/src/Cech_complex/include/gudhi/Sphere_circumradius.h
@@ -0,0 +1,78 @@
+/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
+ *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
+ *    Author(s):       Hind Montassif
+ *
+ *    Copyright (C) 2021 Inria
+ *
+ *    Modification(s):
+ *      - YYYY/MM Author: Description of the modification
+ */
+
+#ifndef SPHERE_CIRCUMRADIUS_H_
+#define SPHERE_CIRCUMRADIUS_H_
+
+#include <CGAL/Epick_d.h> // for #include <CGAL/NT_converter.h> which is not working/compiling alone
+#include <CGAL/Lazy_exact_nt.h> // for CGAL::exact
+
+#include <cmath>  // for std::sqrt
+#include <vector>
+
+namespace Gudhi {
+
+namespace cech_complex {
+
+/** \private @brief Compute the circumradius of the sphere passing through points given by a range of coordinates.
+ * The points are assumed to have the same dimension. */
+template<typename Kernel, typename Filtration_value>
+class Sphere_circumradius {
+ private:
+    Kernel kernel_;
+    const bool exact_;
+ public:
+    using FT = typename Kernel::FT;
+    using Point = typename Kernel::Point_d;
+    using Point_cloud = typename std::vector<Point>;
+
+    CGAL::NT_converter<FT, Filtration_value> cast_to_fv;
+
+   /** \brief Circumradius of sphere passing through two points using CGAL.
+   *
+   * @param[in] point_1
+   * @param[in] point_2
+   * @return Sphere circumradius passing through two points.
+   * \tparam Point must be a Kernel::Point_d from CGAL.
+   *
+   */
+  Filtration_value operator()(const Point& point_1, const Point& point_2) const {
+    auto squared_dist_obj = kernel_.squared_distance_d_object()(point_1, point_2);
+    if(exact_) CGAL::exact(squared_dist_obj);
+    return std::sqrt(cast_to_fv(squared_dist_obj)) / 2.;
+  }
+
+  /** \brief Circumradius of sphere passing through point cloud using CGAL.
+   *
+   * @param[in] point_cloud The points.
+   * @return Sphere circumradius passing through the points.
+   * \tparam Point_cloud must be a range of Kernel::Point_d points from CGAL.
+   *
+   */
+  Filtration_value operator()(const Point_cloud& point_cloud) const {
+    auto squared_radius_obj = kernel_.compute_squared_radius_d_object()(point_cloud.begin(), point_cloud.end());
+    if(exact_) CGAL::exact(squared_radius_obj);
+    return std::sqrt(cast_to_fv(squared_radius_obj));
+  }
+
+  /** \brief Constructor
+   * @param[in] exact Option for exact filtration values computation. Not exact if `Kernel` is not <a target="_blank"
+   * href="https://doc.cgal.org/latest/Kernel_d/structCGAL_1_1Epeck__d.html">CGAL::Epeck_d</a>.
+   * Default is false.
+   */
+  Sphere_circumradius(const bool exact = false) : exact_(exact) {}
+
+};
+
+}  // namespace cech_complex
+
+}  // namespace Gudhi
+
+#endif  // SPHERE_CIRCUMRADIUS_H_