posetJoin -- determines the join for two elements of a poset

• Usage:

  j = posetJoin(P, a, b)

• Inputs:
  • P, an instance of the type Poset,
  • a, a thing, an element of the poset
  • b, a thing, an element of the poset
• Outputs:
  • j, a thing, the least element greater than both $a$ and $b$, if it exists

i1 : B = booleanLattice 3;

i2 : posetJoin(B, "001", "100")

o2 = {101}

o2 : List