ToCanonicalSetPartition[sp, set] reorders sp into a canonical order with respect to set.
ToCanonicalSetPartition[sp] reorders sp into canonical order, assuming that Mathematica knows the underlying order on the set for which sp is a set partition.
To use ToCanonicalSetPartition, you first need to load the Combinatorica Package using Needs["Combinatorica`"].
In the canonical order, the elements of each subset of the set partition are ordered as they appear in set, and the subsets themselves are ordered by their first elements.
