47
Java 21 makes me actually like Java again
(wscp.dev)
I'm not sure I agree that Void is a bottom type. If so, void-functions would never be able to return/terminate. Java's void is probably more of a unit type.
They allude to this later, acknowledging that it's sort of a cross between unit and bottom.
No it's not, it is 100% a unit type (except it's not really a type, since you can only use it as return type and nowhere else)
It's not possible to instantiate or assign, which is more like a never type than a unit; and it is not possible to define new types with the same properties, which is also more like bottom than unit. But you're right that it's not actually a true never type since it can't represent function divergence.
I think the truth is just that Java's type system isn't very mathematically disciplined.
It's not possible to instantiate or assign, which is more like a never type than a unit
Actually, this is because void is not a type, it is just a keyword, a placeholder used instead of the return type when a function doesn't return anything.
If it were a bottom type, that would mean that a method returning void must diverge, which is simply not true.
Also, if it were a bottom type, it would be possible to write an "unreachable" method
void unreachable(void bottom) {
return bottom;
}
Even though it couldn't be called, it should be possible to define it, if void was a bottom type. But it is not, because void isn't a bottom type, it's no type at all.
The post has been edited; it looks like someone on reddit made essentially the same point. You're right of course that void isn't a true type in Java, but the post now also discusses Void, which I suppose just shows how void infects the type system despite not being a type.
It's nice that Java has gotten those features but the article is pretty confused about type theory.
It'll probably take Valhalla for me, personally.
When did you start liking it?
this post was submitted on 16 Sep 2023
47 points (83.1% liked)
Programming
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