The function grelgroup is used as a procedure and an unevaluated procedure call. As a procedure, grelgroup checks its arguments and then either exits with an error or returns the unevaluated grelgroup call.

The first argument is a set of Maple names which stand for the generators of the group. The second argument is a set of ``words'' in the generators. A ``word'' is a list of generators and/or inverses of generators representing a product.  The inverse of a generator  is represented by . An empty list represents the identity element.  The words w1, w2, ..., wn in rels are such that the relations  define the group.

Error, (in grelgroup) relator [a, 1/c, a] contains something (1/c) not a generator or its inverse