The semantics of (), a.k.a. unit, are effectively the same to those of null, and it can be useful to think of it that way. Both null and unit stand for lack of

The semantics of (), a.k.a. unit, are effectively the same to those of null, and it can be useful to think of it that way. Both null and unit stand for lack of information and are placeholders. The difference is in the implementation details. http://en.wikipedia.org/wiki/Unit_type http://en.wikipedia.org/wiki/Unit_type