A position in a term. Arguments are counted from 0.

A position describes a path in the tree representation of a term. The empty position [] denotes the root of the term. A position [0,1] denotes the 2nd child of the 1st child of the root (counting children from left to right).

p `above` q checks whether p is above q (in the tree representation of a term). A position p is above a position q, whenever p is a prefix of q.

p `below` q checks whether p is below q, that is to say that q is above p.

p `parallelTo` q checks whether p is parallel to q, that is to say that p and q do not lie on the same path.

p `leftOf` q checks whether p is left of q. This is only possible if p and q do not lie on the same path (i.e., are parallel to each other).

p `rightOf` q checks whether p is right of q.