This routine returns the interval between the elements a and b in P, including a and b, and an error message if the two elements are not comparable in P.
i1 : P = poset({a,b,c,d},{(a,b),(b,c),(b,d)}); |
i2 : closedInterval(P,a,d) o2 = Poset{cache => CacheTable{} } GroundSet => {a, b, d} RelationMatrix => | 1 1 1 | | 0 1 1 | | 0 0 1 | Relations => {(a, a), (a, b), (a, d), (b, b), (b, d), (d, d)} o2 : Poset |