The join of $a$ and $b$ in $P$, if it exists, is the unique least element greater than both $a$ and $b$.
i1 : P = poset {{a,b}, {a,c}, {a,d}, {c,e}, {d,e}}; |
i2 : joinExists(P, b, c) o2 = false |
i3 : joinExists(P, c, d) o3 = true |
i4 : Q = poset {{a,b}, {a,c}, {b,d}, {c,d}, {b,e}, {c,e}}; |
i5 : joinExists(P, b, c) o5 = false |
The object joinExists is a method function.