Decorates an existing lattice to filter the values before merging them. Warning: Decoration breaks when the decorated lattice has overridden methods except merge and decompose, or uses merge from within merge/decompose.
By assumption: associative, commutative, idempotent.
By assumption: associative, commutative, idempotent.
Implementation note: If it matters, assume that left is the current state and right is an added delta. All code should assume that left is the larger state (and optimize for this). If left == right, prefer to return left.