Why don't we have two nulls?

Question

I\'ve often wondered why languages with a null representing \"no value\" don\'t differentiate between the passive \"I don\'t know what the value is\"

Answer 1

For me null represents lack of value, and I try to use it only to represent that. Of course you can give null as many meanings as you like, just like you can use 0 or -1 to represent errors instead of their numerical values. Giving various meanings to one representation could be ambiguous though, so I wouldn't recommend it.

Your examples can be coded like apple.isRefused() or !apple.isValid() with little work; you should define beforehand what is an invalid apple anyway, so I don't see the gain of having more keywords.