Why Maybe Is Better Than Null

Post by dllthomas » Sat, Apr 20, 2013, 3:42 PM UTC

gizmo686 wrote: post #65

nilkn wrote: post #12

In comparison to Haskell, null in Java is similar to adding an implicit Maybe a instance for every type a. In doing so, Java makes it just that much easier to create bottom values when they are not desired (e.g., dereferencing a null pointer).

I disagree. If null was like Maybe, than you should be able to do: E foo; ... foo=foo.bar().bat() without having to do a null check after each function. I think that Java's approach has the worst of both worlds, because there is no way to make foo.bar().bat() safe when a function could return null. In C, for example, calling a method on a null object does not cause an error. Rather it passes in null as the 'this' val…

Post by chousuke » Sun, Apr 21, 2013, 7:38 AM UTC

stickfigure wrote: post #124

I can't believe there is no mention of Ceylon here. Ceylon has an elegant approach to this using union types. Typesafe null and flow-dependent typing There's no NullPointerException in Ceylon, nor anything similar. Ceylon requires us to be explicit when we declare a value that might be null, or a function that might return null. For example, if name might be null, we must declare it like this: String? name = ... Whic…