Singular Manual: findOrientedBoundary

| #### D.13.4.9 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";
    ==> Welcome to polymake version
    ==> Copyright (c) 1997-2015
    ==> Ewgenij Gawrilow, Michael Joswig (TU Darmstadt)
    ==> http://www.polymake.org
    // 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];
    ==> [1]:
    ==>    0,0
    ==> [2]:
    ==>    1,2
    ==> [3]:
    ==>    2,4
    ==> [4]:
    ==>    3,2
    ==> [5]:
    ==>    3,1
    ==> [6]:
    ==>    2,0
    ==> [7]:
    ==>    1,0
    // the vertices of the boundary are boundarypolygon[2]
    boundarypolygon[2];
    ==> [1]:
    ==>    0,0
    ==> [2]:
    ==>    2,4
    ==> [3]:
    ==>    3,2
    ==> [4]:
    ==>    3,1
    ==> [5]:
    ==>    2,0

User manual for Singular version 4-2-0p1, 2020, generated by texi2html.