anchor.diff:  	     X orelse Y -> true;
   	     true -> false
   	 end,
  -    check(V1, X or Y).
  +    V1 = id(X or Y).
   
   inside(Config) when is_list(Config) ->
       ?line true = inside(-8, 1),
  
positive.code: 
  %% Utilities.
  
  check(V1, V0) ->
      if V1 /= V0 ->
  	    io:fwrite("error: ~w.\n", [V1]),
  	    ?t:fail();
         true ->
  	    io:fwrite("ok: ~w.\n", [V1])
      end.
  
  echo(X) ->	    
      io:fwrite("eval(~w); ",[X]),
      X.
  
negative.code: 	     X andalso Y -> true;
  	     true -> false
  	 end,
      V1 = id(X and Y).
  
  t_orelse_1({X,Y}) ->
      io:fwrite("~w orelse ~w: ",[X,Y]),
  