CGAL users discussion list

[Marc Glisse <>]

On Thu, 12 May 2011, Marc Glisse wrote:

> Indeed, I can't see anything in Lazy.h to interpret the 
> std::vector<Approximate_kernel::Point_3> returned by the approximate kernel 
> to output a std::vector<Lazy_kernel::Point_3> (both wrapped in an Object). 
> And we had better hope that the order of the points in the vector will be the 
> same with the exact kernel (but then I guess the same applies to segments and 
> triangles and is safe enough as long as they use the same deterministic 
> code).

Compiling with -DCGAL_DONT_USE_LAZY_KERNEL would work around this, at the 
price of a slowdown.

The attached patch partially fixes things when the intersection type is 
vector<Point_2> (replace Point_2 by Point_3 in the patch for your case) 
but it forces an exact evaluation in this case because I was too lazy to 
finish it properly.

--
Marc Glisse--- /usr/include/CGAL/Lazy.h    2010-12-15 21:00:40.000000000 +0100
+++ include/CGAL/Lazy.h 2011-05-13 09:23:02.578623203 +0200
@@ -1311,6 +1311,7 @@
   typedef typename LK::Approximate_kernel AK;
   typedef typename LK::Exact_kernel EK;
   typedef typename LK::E2A E2A;
+  typedef Object result_type;
 
   if (eto.is_empty())
     return Object();
@@ -1321,6 +1322,13 @@
 
 #include <CGAL/Kernel/interface_macros.h>
 
+      if(const std::vector<typename 
EK::Point_2>*ptr=object_cast<std::vector<typename EK::Point_2> >(&eto)){
+             std::vector<typename LK::Point_2> ret; ret.reserve(ptr->size());
+             for(typename std::vector<typename EK::Point_2>::const_iterator 
i=ptr->begin();i!=ptr->end();++i)
+                     ret.push_back(typename LK::Point_2(new 
Lazy_rep_0<typename AK::Point_2, typename EK::Point_2, E2A>(*i)));
+             return make_object(ret);
+      }
+
   std::cerr << "object_cast inside Lazy_construction_rep::operator() failed. 
It needs more else if's (#2)" << std::endl;
   std::cerr << "dynamic type of the Object : " << eto.type().name() << 
std::endl;
 
@@ -1657,6 +1665,10 @@
 
 #include <CGAL/Kernel/interface_macros.h>
 
+      if(const std::vector<typename 
AK::Point_2>*ptr=object_cast<std::vector<typename AK::Point_2> 
>(&(lo.approx()))){
+             throw Uncertain_conversion_exception("Quick workaround for 
now");
+      }
+
       std::cerr << "object_cast inside Lazy_construction_rep::operator() 
failed. It needs more else if's (#1)" << std::endl;
       std::cerr << "dynamic type of the Object : " << 
lo.approx().type().name() << std::endl;
 
@@ -1690,6 +1702,11 @@
 
 #include <CGAL/Kernel/interface_macros.h>
 
+      if(const std::vector<typename 
AK::Point_2>*ptr=object_cast<std::vector<typename AK::Point_2> 
>(&(lo.approx()))){
+             throw Uncertain_conversion_exception("Quick workaround for 
now");
+      }
+
+
       std::cerr << "object_cast inside Lazy_construction_rep::operator() 
failed. It needs more else if's (#1)" << std::endl;
       std::cerr << "dynamic type of the Object : " << 
lo.approx().type().name() << std::endl;