anchor.diff:    case D0 of
       {calc, W} ->
         case lists:keyfind(Xi, 1, E) of
  -	{_, E0} ->
  -	  {D1, T1} = eval(E0, I, E, K, D, W, T0),
  -	  tcache:add(Xi, K, D, W, T1, D1);
  -	false ->
  -	  {error, undefined_id, Xi}
  +	      {_, E0} ->
  +	        {D1, T1} = eval(E0, I, E, K, D, W, T0),
  +	        tcache:add(Xi, K, D, W, T1, D1);
  +	      false ->
  +	        {error, undefined_id, Xi}
         end;
       {calc, _W1} ->
         eval2(Xi, I, E, K, D, W, T0 + 1);
  
positive.code:       {D0, T0};
      false ->
        case D0 of
  	true ->
  	  eval(E1, I, E, K, D, W, T0);
  	false ->
  	  eval(E2, I, E, K, D, W, T0)
        end
    end;
  
  
negative.code:       {D0, T0};
      false ->
        case lists:member(D0, D) of
  	      true ->
  	        {lookup_ordinate(D0, K), T0};
  	      false ->
  	        {[D0], T0}
        end
    end;
  
  