i1 : P = poset {{1,4},{2,4},{3,4}};
i2 : adjoinMin(P, 0) o2 = Relation Matrix: | 1 1 0 0 0 | | 0 1 0 0 0 | | 0 1 1 0 0 | | 0 1 0 1 0 | | 1 1 1 1 1 | o2 : Poset