The open interval between a and b is the subposet of P induced by the elements z such that p < z < q. If a and b are incomparable, then an error is thrown.
i1 : P = booleanLattice 3;
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i2 : openInterval(P, "001", "111")
o2 = Relation Matrix: | 1 0 |
| 0 1 |
o2 : Poset
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