## CGAL::Convex_hull_constructive_traits_2<R>

### Definition

The class Convex_hull_constructive_traits_2<R> serves as a traits class for all the two-dimensional convex hull and extreme point calculation function. Unlike the class CGAL::Convex_hull_traits_2<R>, this class makes use of previously computed results to avoid redundancy. For example, in the sidedness tests, lines (of type R::Line_2) are constructed, which is equivalent to the precomputation of subdeterminants of the orientation-determinant for three points.

#include <CGAL/convex_hull_constructive_traits_2.h>

### Is Model for the Concept

ConvexHullTraits_2

### Types

typedef R::Point_2 | Point_2;
typedef R::Less_xy_2
| Less_xy_2;
typedef R::Less_yx_2
| Less_yx_2;
typedef CGAL::r_Less_dist_to_line<R>
| Less_signed_distance_to_line_2;
typedef R::Less_rotate_ccw
| Less_rotate_ccw_2;
typedef R::Left_turn_2
| Left_turn_2;
typedef R::Equal_2 | Equal_2;

### Creation

Convex_hull_constructive_traits_2<R> traits;
| default constructor.

### Operations

Less_xy_2 | traits.less_xy_2_object ()
Less_yx_2 | traits.less_yx_2_object ()
Less_signed_distance_to_line_2
| traits.less_signed_distance_to_line_2_object ()
Less_rotate_ccw_2 | traits.less_rotate_ccw_2_object ()
Left_turn_2 | traits.left_turn_2_object ()
Equal_2 | traits.equal_2_object ()

### See Also

CGAL::Convex_hull_projective_xy_traits_2<Point_3>
CGAL::Convex_hull_projective_xz_traits_2<Point_3>
CGAL::Convex_hull_projective_yz_traits_2<Point_3>
CGAL::Convex_hull_traits_2<R>