void in Java and Void in Haskell are quite different. As the post explains, in Haskell it’s a type with no possible values. In Java, the equivalent would be a class without a constructor (not sure if that’s even possible). It defines a type, but you cannot construct a value or object with that type. The equivalent of Java‘s void in Haskell is the unit type () which has exactly one possible value, also called (). It can be returned by a function, but it does not give you any information, just like void. By the way, Rust also uses the unit type instead of void.

I’ve first read this post back in 2019 when it was released and I have to say that it really has left quite an impact on the way I write programs these days. The „make illegal states unrepresentable“ and „push proofs up“ guidelines are so simple yet so effective. Sure, there is some initial cost to create new datatypes, but it really pays off in the long run. Not having to worry about null or wrongly shaped data structures down the line is really nice, especially if you’re working on older code or develop in a team. Even though the post uses Haskell to explain the concepts, I found it to also work well in other languages, even Java or Python.

In Firefox, you can also override right-click capture by holding shift while right-clicking.