While there was a strong link between social class and facial symmetry in men, the connection in women was less clear.

The "obvious" ways to define equals when extending an instantiable class that already overrides equals all fail to meet the symmetry or transitivity requirements of the equals method.

The class idempotent function composing systems of orthogonal idempotents is one of the fundamental tools in constructing symmetry functions and it plays an important role in symmetry designs.