Function check

Geometry/Geometry 2D.cpp:1068–1070

    }
};
int check(HP a, HP b, HP c) {
    return cross(a.b - a.a, b.intersection(c) - a.a) > -eps; //-eps to include polygons of zero area (straight lines, points)
}
// consider half-plane of counter-clockwise side of each line
// if lines are not bounded add infinity rectangle
// returns a convex polygon, a point can occur multiple times though