NUMs > MAX_VARS, so you may
have to rename variables of the result before calling a unification
routine on the result.
<P>
Unification and matching can be used incrementally.  For example,
you can all unify() with a context which has entries from a
previous call to unify().  Hyperresolution can be implemented by
backtracking through the negative literals of a nucleus
and the satellites that unify with a given literal of the nucleus,
constructing and undoing partial substitutions along the way.
Another examp