code: function(or, and) {
  			var aDiff = set.difference(or, and.values[0]);
  			var bDiff = set.difference(or, and.values[1]);
  			return set.union(aDiff, bDiff);
  		}
docs: (a ∪ b) \ (c ∩ d) where Z = (a ∪ b) -> Z \ (c ∩ d) -> (Z \ c) ∪ (Z \ d) -> ((a ∪ b) \ c) ∪ ((a ∪ b) \ d)