anchor.diff:  %% returns {{Module,Function,Arity},[{Head,Cond,Body}],[Flag]}
   compile({M,F,'_',[],Actions}) ->
     {{M,F,'_'},[{'_',[],compile_acts(Actions)}],flags()};
  +compile({_,_,'_',Gs,_}) ->
  +  exit({guards_without_args,Gs});
   compile({M,F,Ari,[],Actions}) when is_integer(Ari) ->
     compile({M,F,lists:duplicate(Ari,{var,'_'}),[],Actions});
   compile({M,F,As,Gs,Actions}) when is_list(As) ->
  
positive.code:       {{a,b,2},[{['$1','$2'],[{'==','$1',1},{'=/=','$2',a}],[]}],[local]}}
       ,{"a:b(X,y)when not is_atom(X) -> return",
         {{a,b,2},
          [{['$1',y],[{'not',{is_atom,'$1'}}],[{return_trace}]}],
          [local]}}
       ,{"a:b(X,y)when element(1,X)==foo, (X==z)",
         {{a,b,2},
  
negative.code:     fun(Str,O)->[unit(fun transform/1,Str)|O]end,[],
      [{"a",
        {{a,'_','_'},[{'_',[],[]}],[local]}}
       ,{"a",
         {{a,'_','_'},[{'_',[],[]}],[local]}}
       ,{"a->stack",
         {{a,'_','_'},[{'_',[],[{message,{process_dump}}]}],[local]}}
       ,{"a:b",
         {{a,b,'_'},[{'_',[],[]}],[local]}}
       ,{"a:b->return ",
         {{a,b,'_'},[{'_',[],[{exception_trace}]}],[local]}}
       ,{"a:b/2",
         {{a,b,2},[{['_','_'],[],[]}],[local]}}
       ,{"a:b/2->return",
         {{a,b,2},[{['_','_'],[],[{exception_trace}]}],[local]}}
       ,{"a:b(X,Y)",
         {{a,b,2},[{['$1','$2'],[],[]}],[local]}}
       ,{"a:b(_,_)",
  