奇怪的是，使用boost :: geometry :: within（）来表示多边形和环形

Question

我在 Debian 9 上开发了一个应用程序，其中{strong> boost-1.62.0 安装在{{1>命令。我发现在调用sudo apt-get install时有一种奇怪的行为。多边形与环相交，但不与in相交。以下是代码：

boost::geometry::with_in(polygon, ring)

构建并运行：

#include <iostream>
#include <boost/geometry/algorithms/intersection.hpp>
#include <boost/version.hpp>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/ring.hpp>
#include <boost/geometry/geometries/polygon.hpp>

using namespace std;
using namespace boost;
using namespace boost::geometry;

int main()
{
    using Point = boost::geometry::model::d2::point_xy<double>;
    using Polygon = boost::geometry::model::polygon<Point>;
    using Ring = boost::geometry::model::ring<Point>;

    Ring outer;
    append(outer, Point(-6.46720129179205, 15.61591992211971));
    append(outer, Point(-3.617204647384145, 15.61591992211971));
    append(outer, Point(-3.617204647384145, 7.615919922119708));
    append(outer, Point(-6.46720129179205, 7.615919922119708));
    append(outer, Point(-6.46720129179205, 15.61591992211971));

    Polygon polygon;
    polygon.outer() = outer;
    correct(polygon);

    Ring ring;
    append(ring, Point(-3.542202969588097, 7.615919922119709));
    append(ring, Point(-3.542202969588097, 6.81591992211971));
    append(ring, Point(-3.542202969588097, 6.015919922119708));
    append(ring, Point(-3.542202969588097, 5.215919922119708));
    append(ring, Point(-3.542202969588097, 4.415919922119708));
    append(ring, Point(-3.542202969588097, 3.615919922119708));
    append(ring, Point(-3.542202969588097, 2.815919922119709));
    append(ring, Point(-3.542202969588097, 2.015919922119709));
    append(ring, Point(-3.542202969588097, 1.215919922119709));
    append(ring, Point(-3.542202969588097, 0.4159199221197081));
    append(ring, Point(-3.542202969588097, -0.3840800778802915));
    append(ring, Point(-6.542202969588097, -0.3840800778802916));
    append(ring, Point(-6.542202969588097, 0.415919922119708));
    append(ring, Point(-6.542202969588097, 1.215919922119709));
    append(ring, Point(-6.542202969588097, 2.015919922119709));
    append(ring, Point(-6.542202969588097, 2.815919922119709));
    append(ring, Point(-6.542202969588097, 3.615919922119708));
    append(ring, Point(-6.542202969588096, 4.41591992211971));
    append(ring, Point(-6.542202969588097, 5.215919922119709));
    append(ring, Point(-6.542202969588097, 6.015919922119709));
    append(ring, Point(-6.542202969588097, 6.815919922119708));
    append(ring, Point(-6.542202969588097, 7.615919922119708));
    append(ring, Point(-3.542202969588097, 7.615919922119709));
    correct(ring);

    cout << boolalpha
         << within(polygon, ring) << endl /* should return false */
         << covered_by(polygon, ring) << endl; /* should retrurn false */

    return 0;
}

获得结果：

 g++ -g -o wi wi.cpp
 ./wi

内部多边形 不是 ，但 true true 返回boost::geometry::within(polygon, ring)。

那么boost-1.62错误呢？以及如何解决它。

Answer 1

差价7.615919922119709 - 7.615919922119708是1×10 ^ -15。

这意味着几何图形垂直重叠。根据标准的简单特征规范，这意味着它们满足within：

Create solid polygon in boost geometry