\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - 2D Arrangements

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Arrangement_on_surface_2/edge_manipulation_curve_history.cpp
// Removing curves and manipulating edges in an arrangement with history.
#include <CGAL/Cartesian.h>
#include <CGAL/Exact_rational.h>
#include <CGAL/Arr_circle_segment_traits_2.h>
#include <CGAL/Arrangement_with_history_2.h>
typedef CGAL::Cartesian<CGAL::Exact_rational> Kernel;
typedef Kernel::Point_2 Rat_point_2;
typedef Kernel::Circle_2 Circle_2;
typedef CGAL::Arr_circle_segment_traits_2<Kernel> Traits_2;
typedef Traits_2::Point_2 Point_2;
typedef Traits_2::Curve_2 Curve_2;
typedef CGAL::Arrangement_with_history_2<Traits_2> Arr_with_hist_2;
typedef Arr_with_hist_2::Curve_handle Curve_handle;
typedef CGAL::Arr_walk_along_line_point_location<Arr_with_hist_2>
Point_location;
int main()
{
// Construct an arrangement containing nine circles: C[0] of radius 2 and
// C[1], ..., C[8] of radius 1.
const CGAL::Exact_rational _7_halves = CGAL::Exact_rational(7, 2);
Arr_with_hist_2 arr;
Curve_2 C[9];
Curve_handle handles[9];
C[0] = Circle_2(Rat_point_2(_7_halves, _7_halves), 4, CGAL::CLOCKWISE);
C[1] = Circle_2(Rat_point_2(_7_halves, 6), 1, CGAL::CLOCKWISE);
C[2] = Circle_2(Rat_point_2(5, 6), 1, CGAL::CLOCKWISE);
C[3] = Circle_2(Rat_point_2(6, _7_halves), 1, CGAL::CLOCKWISE);
C[4] = Circle_2(Rat_point_2(5, 2), 1, CGAL::CLOCKWISE);
C[5] = Circle_2(Rat_point_2(_7_halves, 1), 1, CGAL::CLOCKWISE);
C[6] = Circle_2(Rat_point_2(2, 2), 1, CGAL::CLOCKWISE);
C[7] = Circle_2(Rat_point_2(1, _7_halves), 1, CGAL::CLOCKWISE);
C[8] = Circle_2(Rat_point_2(2, 5), 1, CGAL::CLOCKWISE);
size_t k;
for (k = 0; k < 9; k++)
handles[k] = insert(arr, C[k]);
std::cout << "The initial arrangement size:" << std::endl
<< " V = " << arr.number_of_vertices()
<< ", E = " << arr.number_of_edges()
<< ", F = " << arr.number_of_faces() << std::endl;
// Remove the large circle C[0].
std::cout << "Removing C[0] : ";
std::cout << remove_curve(arr, handles[0])
<< " edges have been removed." << std::endl;
std::cout << "The arrangement size:" << std::endl
<< " V = " << arr.number_of_vertices()
<< ", E = " << arr.number_of_edges()
<< ", F = " << arr.number_of_faces() << std::endl;
// Locate the point q, which should be on an edge e.
Point_location pl(arr);
const Point_2 q = Point_2(_7_halves, 7);
Point_location::result_type obj = pl.locate(q);
Arr_with_hist_2::Halfedge_const_handle e;
CGAL_assertion_code(bool success = ) CGAL::assign(e, obj);
CGAL_assertion(success);
// Split the edge e to two edges e1 and e2;
Arr_with_hist_2::Halfedge_handle e1, e2;
e1 = arr.split_edge(arr.non_const_handle(e), q);
e2 = e1->next();
std::cout << "After edge split: "
<< "V = " << arr.number_of_vertices()
<< ", E = " << arr.number_of_edges()
<< ", F = " << arr.number_of_faces() << std::endl;
// Merge back the two split edges.
arr.merge_edge(e1, e2);
std::cout << "After edge merge: "
<< "V = " << arr.number_of_vertices()
<< ", E = " << arr.number_of_edges()
<< ", F = " << arr.number_of_faces() << std::endl;
return 0;
}