fix shortest_non_loop_edge

Triangulation_on_hyperbolic_surface_2/doc/Triangulation_on_hyperbolic_surface_2/CGAL/Delaunay_triangulation_on_hyperbolic_surface_2.h

@@ -202,7 +202,7 @@ public:
   */
   double shortest_loop() const;
   /*!
-    \return a `double` approximation of the length of the shortest non-loop edge in the Delaunay triangulation.
+    \return a `double` approximation of the length of the shortest non-loop edge in the Delaunay triangulation. Returns 0 (NULL) if all edges are loops.
   */
   double shortest_non_loop_edge() const;
   /// @}

Triangulation_on_hyperbolic_surface_2/include/CGAL/Delaunay_triangulation_on_hyperbolic_surface_2.h

@@ -1094,6 +1094,7 @@ Delaunay_triangulation_on_hyperbolic_surface_2<Traits>::
 shortest_non_loop_edge() const
 {
     Number min_delta_length = 999;
+    double res = NULL;
     for (typename Edge_const_range::const_iterator it = this->combinatorial_map_.template one_dart_per_cell<1>().begin();
                                        it != this->combinatorial_map_.template one_dart_per_cell<1>().end(); ++it) {
         Anchor const & current_anchor = anchor(it);
@@ -1112,10 +1113,11 @@ shortest_non_loop_edge() const
         }
         if(!is_loop) {
             Number delta_length = delta(a, b);
-            min_delta_length = min(min_delta_length,delta_length);
+            min_delta_length = min(min_delta_length, delta_length);
+            res = std::acosh(1 + to_double(min_delta_length));
         }
     }
-    return std::acosh(1 + to_double(min_delta_length));
+    return res;
 }
 
 }  // namespace CGAL

Triangulation_on_hyperbolic_surface_2/test/Triangulation_on_hyperbolic_surface_2/hs_test_Delaunay_triangulation.cpp

@@ -80,7 +80,7 @@ int main()
     assert(same_vertices);
 
     assert(dt.shortest_loop() != 0);
-    assert(dt.shortest_non_loop_edge() != 0);
+    assert(dt.shortest_non_loop_edge() == 0);
 
     return 0;
 }

Triangulation_on_hyperbolic_surface_2/test/Triangulation_on_hyperbolic_surface_2/hs_test_espilon_net.cpp

@@ -60,6 +60,7 @@ int main(int argc, char *argv[])
 
     assert(is_eps_net);
     assert(dt.is_valid());
+    assert(dt.shortest_non_loop_edge() != 0);
 
     return 0;
 }