anchor.diff:  
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   %%% ad-hoc unit testing
  +
  +unit_loud() ->
  +  lists:foreach(fun(R)->io:fwrite("~p~n",[R])end,unit()).
   
   unit_quiet() ->
     [R||R<-unit(),is_tuple(R)].
  
positive.code:       end
    end.
  
  disjunct_guard(Toks) ->  %% replace ';' with 'orelse'
    [case T of {';',1} -> {'orelse',1}; _ -> T end||T<-Toks].
  
  guard({call,1,{atom,1,G},Args}) -> {G,[arg(A) || A<-Args]};   % function
  
negative.code:      ,{"a:b when element(1,'$_')=/=c",
         {{a,b,'_'},
          [{'_',[{'=/=',{element,1,'$_'},c}],[]}],[local]}}
       ,{"a",
         {{a,'_','_'},[{'_',[],[]}],[local]}}
       ,{"a->stack",
  