anchor.diff:  
      ok.
   
  +-define(GUARD(E), if E -> true;
  +		     true -> false
  +		  end).
  +
   t_andalso(Config) when is_list(Config) ->
       Bs = [true,false],
       Ps = [{X,Y} || X <- Bs, Y <- Bs],
  
positive.code:     ?line false = true andalso false,
      ?line false = false andalso true,
      ?line false = false andalso false,
  
      ?line false = false andalso glurf,
      ?line false = false andalso exit(exit_now),
  
negative.code:     ?line true = true orelse false,
      ?line true = false orelse true,
      ?line false = false orelse false,
  
      ?line true = ?GUARD(true orelse true),
      ?line true = ?GUARD(true orelse false),
      ?line true = ?GUARD(false orelse true),
      ?line false = ?GUARD(false orelse false),
  
      ?line true = true orelse glurf,
      ?line true = true orelse exit(exit_now),
  