CGAL example cannot read input files? - cgal

Question

this is my first stackoverflow question, so I hope the following text meets the question requirements. If not, please tell me what needs to be changed so I can adapt the question.
I'm new to CGAL and C++ in general. I would like to use CGAL 5.0.2 on a Macbook Pro early 2015 with macOS Catalina Version 10.15.4.
So to begin with, I followed the instruction steps given by the CGAL documentation using the package manager Homebrew. Since CGAL is a header-only library I configured it using CMake, as is recommended by the documentation.
It all worked out fine, so I went on trying the recommended examples given in the file CGAL-5.0.2.tar.xz, which is provided here. I'm particularly interested in the example Voronoi_Diagram_2.
Using the Terminal I executed the command -DCGAL_DIR=$HOME/CGAL-5.0.2 -DCMAKE_BUILD_TYPE=Release . in the example folder called Voronoi_Diagram_2. Then I executed the command make. All went well, no error messages were prompted. But executing the resulting exec file didn't produce any results.
After some research I managed to modify the code in a way that it prints the values of some variables. Problem seems to be that the input file which contains the line segments for which the voronoi diagramm shall be calculated is not correctly read.
The while loop which I highlighted in the code below by inserting //// signs seems not to be entered. That's why I assume that the variable ifs is empty, even though the input file "data1.svd.cin", which can be found in the folder "data" of the example, wasn't.
Does anyone have an idea for the reasons of this behaviour? Any help is appreciated.
This is the vd_2_point_location_sdg_linf.cpp file included in the example, which I modified:
// standard includes
#include <iostream>
#include <fstream>
#include <cassert>
// includes for defining the Voronoi diagram adaptor
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Segment_Delaunay_graph_Linf_filtered_traits_2.h>
#include <CGAL/Segment_Delaunay_graph_Linf_2.h>
#include <CGAL/Voronoi_diagram_2.h>
#include <CGAL/Segment_Delaunay_graph_adaptation_traits_2.h>
#include <CGAL/Segment_Delaunay_graph_adaptation_policies_2.h>
// typedefs for defining the adaptor
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Segment_Delaunay_graph_Linf_filtered_traits_2<K> Gt;
typedef CGAL::Segment_Delaunay_graph_Linf_2<Gt> DT;
typedef CGAL::Segment_Delaunay_graph_adaptation_traits_2<DT> AT;
typedef CGAL::Segment_Delaunay_graph_degeneracy_removal_policy_2<DT> AP;
typedef CGAL::Voronoi_diagram_2<DT,AT,AP> VD;
// typedef for the result type of the point location
typedef AT::Site_2 Site_2;
typedef AT::Point_2 Point_2;
typedef VD::Locate_result Locate_result;
typedef VD::Vertex_handle Vertex_handle;
typedef VD::Face_handle Face_handle;
typedef VD::Halfedge_handle Halfedge_handle;
typedef VD::Ccb_halfedge_circulator Ccb_halfedge_circulator;
void print_endpoint(Halfedge_handle e, bool is_src) {
std::cout << "\t";
if ( is_src ) {
if ( e->has_source() ) std::cout << e->source()->point() << std::endl;
else std::cout << "point at infinity" << std::endl;
} else {
if ( e->has_target() ) std::cout << e->target()->point() << std::endl;
else std::cout << "point at infinity" << std::endl;
}
}
int main()
{
std::ifstream ifs("data/data1.svd.cin");
assert( ifs );
VD vd;
Site_2 t;
// /////////// Inserted Comment ////////////////////////////////
std::cout << "In the following the insertion from ifs should take place" << std::flush;
// ///////////////// while loop which doesn't seem to be active //////////////////
while ( ifs >> t ) {
// Existing Code to insert the points in the voronoi structure
vd.insert(t);
// Inserted Code to check if while loop is entered
std::cout << "Entered while loop" << std::flush;
}
// ///////////////////////////////////////////////////////////////////////////////
ifs.close();
assert( vd.is_valid() );
std::ifstream ifq("data/queries1.svd.cin");
assert( ifq );
Point_2 p;
while ( ifq >> p ) {
std::cout << "Query point (" << p.x() << "," << p.y()
<< ") lies on a Voronoi " << std::flush;
Locate_result lr = vd.locate(p);
if ( Vertex_handle* v = boost::get<Vertex_handle>(&lr) ) {
std::cout << "vertex." << std::endl;
std::cout << "The Voronoi vertex is:" << std::endl;
std::cout << "\t" << (*v)->point() << std::endl;
} else if ( Halfedge_handle* e = boost::get<Halfedge_handle>(&lr) ) {
std::cout << "edge." << std::endl;
std::cout << "The source and target vertices "
<< "of the Voronoi edge are:" << std::endl;
print_endpoint(*e, true);
print_endpoint(*e, false);
} else if ( Face_handle* f = boost::get<Face_handle>(&lr) ) {
std::cout << "face." << std::endl;
std::cout << "The vertices of the Voronoi face are"
<< " (in counterclockwise order):" << std::endl;
Ccb_halfedge_circulator ec_start = (*f)->ccb();
Ccb_halfedge_circulator ec = ec_start;
do {
print_endpoint(ec, false);
} while ( ++ec != ec_start );
}
std::cout << std::endl;
}
ifq.close();
return 0;
}