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D.13.1.12 findOrientedBoundary

Procedure from library polymake.lib (see polymake_lib).

Usage:
findOrientedBoundary(polygon); polygon list

Assume:
polygon is a list of integer vectors defining integer lattice points in the plane

Return:
list l with the following interpretation
l[1] = list of integer vectors such that the polygonal path defined by these is the boundary of the convex hull of the lattice points in polygon
l[2] = list, the redundant points in l[1] have been removed

Example:
 
LIB "polymake.lib";
// the following lattice points in the plane define a polygon
list polygon=intvec(0,0),intvec(3,1),intvec(1,0),intvec(2,0),
intvec(1,1),intvec(3,2),intvec(1,2),intvec(2,3),
intvec(2,4);
// we compute its boundary
list boundarypolygon=findOrientedBoundary(polygon);
// the points on the boundary ordered clockwise are boundarypolygon[1]
boundarypolygon[1];
// the vertices of the boundary are boundarypolygon[2]
boundarypolygon[2];