songsenand
/
cgal
mirror of https://github.com/CGAL/cgal
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Made the polyline traits a practical model of the ArrangementLandmarkTraits concept only if the segment traits is a model of this concept

This commit is contained in:
Efi Fogel 2013-07-22 14:58:11 +03:00
parent 7dd3f395e2
commit d6a7413cdb
1 changed files with 63 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h
View File

@ -1732,14 +1732,73 @@ namespace CGAL {
/// \name Functor definitions for the landmarks point-location strategy.
//@{
typedef typename Segment_traits_2::Approximate_number_type
Approximate_number_type;
typedef typename Segment_traits_2::Approximate_2 Approximate_2;
#if 0
// The following block assumes that the segment traits template parameter
// is a model of the ArrangementLandmarkTraits concept; in other words, it
// defines the nested types Approximate_number_type and Approximate_2 and
// the member function approximate_2_object(). It cannot be used as is if
// the segment traits does not model the ArrangementLandmarkTraits concept.
// The functor Construct_x_monotone_curve_2 is provided regardless of the
// segment traits.
typedef typename Segment_traits_2::Approximate_number_type
Approximate_number_type;
typedef typename Segment_traits_2::Approximate_2 Approximate_2;
/*! Get an Approximate_2 functor object. */
Approximate_2 approximate_2_object() const
{ return segment_traits_2()->approximate_2_object(); }
#else
// The following block defines the nested types Approximate_number_type and
// Approximate_2 and the member function approximate_2_object() based on the
// corresponding types and function definitions of the segment traits. If
// the segment traits does not provide these definitions, they are defined
// as dummies. Essentially, the polyline traits becomes a practical model of
// the ArrangementLandmarkTraits concept only if the segment traits is a
// model of this concept.
//
// The following implementation is inspired by
// http://stackoverflow.com/a/11816999/1915421
template <typename T>
struct Void {
typedef void type;
};
template <typename T, typename _ = void>
struct has_approximate_2 {
// Generic implementation
typedef void Approximate_number_type;
typedef void Approximate_2;
};
template <typename T>
struct has_approximate_2<T, typename Void<typename T::Approximate_2>::type>
{
// Specialization for types holding a nested type T::Approximate_2
typedef typename T::Approximate_number_type
Approximate_number_type;
typedef typename T::Approximate_2 Approximate_2;
};
typedef typename has_approximate_2<Segment_traits_2>::Approximate_number_type
Approximate_number_type;
typedef typename has_approximate_2<Segment_traits_2>::Approximate_2
Approximate_2;
/*! Get an Approximate_2 functor object. */
Approximate_2 approximate_2_object_impl(boost::false_type) const
{ return segment_traits_2()->approximate_2_object(); }
Approximate_2 approximate_2_object_impl(boost::true_type) const { }
Approximate_2 approximate_2_object() const
{
typedef typename boost::is_same<void, Approximate_2>::type Is_void;
return approximate_2_object_impl(Is_void());
}
#endif
class Construct_curve_2 {
protected:
@ -1773,7 +1832,7 @@ namespace CGAL {
Curve_2 operator()(ForwardIterator begin, ForwardIterator end) const
{
typedef typename std::iterator_traits<ForwardIterator>::value_type VT;
typedef typename boost::is_same<VT,Point_2>::type Is_point;
typedef typename boost::is_same<VT, Point_2>::type Is_point;
// Dispatch the range to the appropriate implementation.
return constructor_impl(begin, end, Is_point());
}