| max_var_number/3 | True when Max is the max of Start and the highest numbered $VAR(N) term. |
| numbervars/1 | Number variables in Term using $VAR(N). |
| varnumbers/2 | Inverse of numbervars/1. |
| varnumbers/3 | Inverse of numbervars/3. |
| varnumbers_names/3 | If Term is a term with numbered and named variables using the reserved term’$VAR’(X), Copy is a copy of Term where each’$VAR’(X) is consistently replaced by a fresh variable and Bindings is a list‘X = Var`, relating the‘X` terms with the variable it is mapped to. |