/*
 *  call-seq:
 *     term_enum.next -> term_string
 *
 *  Returns the next term in the enumeration or nil otherwise.
 */
static VALUE
frt_te_next(VALUE self)
{
    TermEnum *te = (TermEnum *)DATA_PTR(self);
    return frt_te_get_set_term(self, te->next(te));
}