CGAL 5.1.3  Triangulated Surface Mesh Simplification

#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Constrained_placement.h>
Get_placement_.
The class Constrained_placement
is a model for the concept GetPlacement
.
The placement of the vertex resulting from a contraction of an edge adjacent to a constrained edge is the point of the common vertex. Otherwise the placement is the one computed by Get_placement_
.
Get_placement_  must be a model of GetPlacement . 
Edge_is_constrained_map_  must be a model of ReadablePropertyMap with Edge_profile::edge_descriptor as key type and bool as value type indicating if an edge is constrained. 
Creation  
Constrained_placement (Edge_is_constrained_map_ map=Edge_is_constrained_map_(), const Get_placement_ &get_placement=Get_placement_())  
Constructor.  