code: function(gt, or) {
  
  		var or1 = or.values[0],
  			or2 = or.values[1];
  		var difference1 = set.difference(gt, or1);
  		var difference2 = set.difference(gt, or2);
  		return set.intersection(difference1, difference2);
  	}
docs: v \ (a || b) -> (v \ a) n (v \ b)