anchor.diff:      vars_of(Xs, vars_of(X, Vs));
   vars_of([], Vs) ->
       Vs;
  -vars_of(X, Vs) ->
  +vars_of(_X, Vs) ->
       %% cannot be a variable or contain a variable
       Vs.
   
  
positive.code:       end,
        Form
       );
  resolve_form(Form, FuncDefs) ->
      Form.
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
negative.code: 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  clauses_arity([{clause, _, H, _G, _B}|_]) ->
      length(H).
  
  %%
  