add method to access the sum of weights

Generator/include/CGAL/internal/Generic_random_point_generator.h

@@ -84,6 +84,12 @@ public:
     ++(*this);
     return tmp;
   }
+  double sum_of_weights() const
+  {
+    if (weights.empty())
+      return 0;
+    return weights.back();
+  }
 };
 
 template < typename Id, class ObjectFromIdMap, class GeneratorOnObject, class P >

Generator/include/CGAL/point_generators_3.h

@@ -347,6 +347,10 @@ public:
   ++(*this);
   return tmp;
  }
+  double mesh_area() const
+  {
+    this->sum_of_weights();
+  }
 };
 
 namespace internal