anchor.diff:       ,{"a:b when element(1,'$_')=/=c",
          {{a,b,'_'},
           [{'_',[{'=/=',{element,1,'$_'},c}],[]}],[local]}}
  -     ,{"a",
  -       {{a,'_','_'},[{'_',[],[]}],[local]}}
        ,{"a",
          {{a,'_','_'},[{'_',[],[]}],[local]}}
        ,{"a->stack",
  
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: 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %%% 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)].
  