i1 : P = poset ({a,b,c}, {(a,b), (a,c)});
i2 : compare (P,a,c) o2 = true
i3 : compare (P,c,a) o3 = false
i4 : compare (P,b,c) o4 = false
Note that if two elements are not comparable, compare still returns a value of false.