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)});
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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
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