anchor.diff:      case Dm:asserta_clause(Dr0, Functor, Head, Body) of
   	{ok,Dr1} -> Db#db{ref=Dr1};
   	error ->
  -	    permission_error(modify, static_procedure, pred_ind(Functor), Db)
  +	    permission_error(modify, static_procedure, pred_ind(Functor))
       end.
   
   assertz_clause({':-',H,B}, Db) -> assertz_clause(H, B, Db);
  
positive.code: 
  %% Error types.
  -export([erlog_error/1,erlog_error/2,type_error/2,type_error/3,
  	 instantiation_error/0,instantiation_error/1,permission_error/4]).
  
  %%-compile(export_all).
  
  
negative.code:     prove_current_predicate(Pi, Next, St);
  prove_goal({predicate_property,H0,P}, Next, #est{bs=Bs,db=Db}=St) ->
      H = dderef(H0, Bs),
      try get_procedure_type(functor(H), Db) of
  	built_in -> unify_prove_body(P, built_in, Next, St);
  	compiled -> unify_prove_body(P, compiled, Next, St);
  	interpreted -> unify_prove_body(P, interpreted, Next, St);
  	undefined -> ?FAIL(St)
      catch
  	throw:{erlog_error,E} ->
  	    erlog_error(E, St)	                %Add state to error
      end;
  %% All solutions.
  prove_goal({findall,T,G,L}, Next, St) ->
  