Opened 6 years ago

#12929 new Bugs

linestring with zero points or a single point is not equal to itself

Reported by: Michael Maier <m-maier@…> Owned by: Barend Gehrels
Milestone: To Be Determined Component: geometry
Version: Boost 1.60.0 Severity: Problem
Keywords: Cc:

Description

I expect a linestring with zero points or a single point is equal to itself. However, this is not the case for boost::geometry::equals even though the documentation says

Checks if a geometry are spatially equal.

Spatially equal means that the same point set is included.

I expect a linestring with zero points to be equal to all empty point sets. I expect a linestring with a single point to be equal to all single point sets where the single points are equal.

Example: 

#include <iostream>

#include <boost/geometry.hpp>

namespace bg = boost::geometry;

using point = bg::model::point<double, 2, bg::cs::cartesian>;
using linestring = bg::model::linestring<point>;

int main() {
    linestring empty;
    linestring single_point_linestring {{0.0, 0.0}};
    linestring single_point_linestring_2 {{0.0, 0.0}};

    std::cout << "empty == empty := " << bg::equals(empty, empty) << '\n';
    std::cout << "single_point_linestring == single_point_linestring := "
              << bg::equals(single_point_linestring, single_point_linestring) << '\n';
    std::cout << "single_point_linestring == single_point_linestring_2 := "
              << bg::equals(single_point_linestring, single_point_linestring_2) << '\n';
}

Output: 

empty == empty := 0
single_point_linestring == single_point_linestring := 0
single_point_linestring == single_point_linestring_2 := 0

Expected: 

empty == empty := 1
single_point_linestring == single_point_linestring := 1
single_point_linestring == single_point_linestring_2 := 1

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