Add a convenience function for the idiom "if(obj.is<Point>())"...

STL_Extension/doc_tex/STL_Extension_ref/Object.tex

@@ -40,6 +40,9 @@ Objects of type \ccRefName\ are normally created using the global function
 \ccMethod{bool empty();}{returns true, if \ccVar\ does not 
         contain an object.}
 
+\ccMethod{template<class T> bool is();}
+{returns true, iff \ccVar\ contains an object of type \ccc{T}.}
+
 \ccMethod{const std::type_info & type() const;}
          {returns the type information of the contained type,
           or \ccc{typeid(void)} if empty.}

STL_Extension/include/CGAL/Object.h

@@ -131,6 +131,12 @@ class Object
 	return empty();
     }
 
+    template <class T>
+    bool is() const
+    {
+        return NULL != dynamic_cast<const Wrapper<T> *>(Ptr());
+    }
+
     const std::type_info & type() const
     {
         return empty() ? typeid(void) : Ptr()->type();