de.rwth.domains
Interface PreUpperSemiLattice

All Superinterfaces:

POSet, Set

All Known Subinterfaces:

CompleteLattice, Lattice, PreLattice, UpperSemiLattice

public interface PreUpperSemiLattice

extends POSet

Interface for pre upper semi lattices. Pre upper semi lattices are partially ordered sets, where the least upper bound might not exist for two elements.

Version:

$Id: PreUpperSemiLattice.java,v 1.2 2002/09/17 06:53:53 mohnen Exp $

Author:

Markus Mohnen

Inner classes inherited from class de.rwth.domains.Set

Set.Default

Method Summary

java.lang.Object

join(java.lang.Object e1, java.lang.Object e2) Computes the least upper bound of two elements if it exists.

Methods inherited from interface de.rwth.domains.POSet

le, lt

Methods inherited from interface de.rwth.domains.Set

equals, isElement, iterator, iteratorSkel, size, sizeSkel

Method Detail

join

public java.lang.Object join(java.lang.Object e1,
                             java.lang.Object e2)

Computes the least upper bound of two elements if it exists.
Implementations should guarantee that join is commutative and associative. Furthermore, join(e1,e2)=e2 iff le(e1,e2). If one of the arguments is null, the result must be null as well.

Parameters:

e1 - a value of type Object

e2 - a value of type Object

Returns:

the least upper bound of e1 and e2 or null if this does not exists

See Also:

Domain.checkProperties(PreUpperSemiLattice pusl)