[ukj]

So, there is nothing dynamic about that dispatch.

Because the implementation details of Foo are actually know at compile time. Which is why you are able to type-check it.

You have literally declared all allowed (but not all possible) implementations of Foo.

What happens when Foo() is a remote/network call?

[justinpombrio]

That is not what dynamic dispatch means! It is an extremely well established term, with a very clear meaning, and that is not what it means.

I thought you were just mistaken about something, but no, instead you've redefined a well understood term without telling anyone, then aggressively refused to clarify what you meant by it and argued for hours with people, while saying they were all wrong when they used the well established term to mean its well established meaning.

The thing you're talking about is an interesting concept, but it's not called dynamic dispatch, and you will confuse everyone you talk to if you call it that. I don't know if there's a term for it.

[ukj]

“Well established” doesn’t mean anything.

According to who?

Computer scientists talk about “well formed” not “well established”.

Those are categorical definitions.

[justinpombrio]

> According to who?

Wikipedia, every textbook you can find, the top dozen search results for "dynamic dispatch", me who has a PhD in computer science plus all the other CS PhD people I know, everyone in my office who knows the term (who are industry people, not academia people), every blog post I have ever read that uses the term, and all the other HN commenters except you. I'm really not exaggerating; a lot of CS terms have disputed meanings but not this one.

EDIT: Sorry all for engaging the troll. I thought there might have been some legitimate confusion. My bad.

[ukj]

There is a legitimate confusion indeed and it seems to be on your part!

What I am talking about when I say "dynamic dispatch" is the sort of dispatching done by R, LISP and Julia (and not by C++ or Java). Now, we can bicker about labels and you can insist that it's actually called "multiple dispatch" and not "dynamic dispatch", but you can't bicker about the semantic fact that "multiple dispatch" is actually more dynamic than "dynamic dispatch".

And this semantic point would've been trivial to unpack if you weren't try to win an argument.

Indeed, sorry for engaging the trolls. 20; or 30 of you. Lost count.

[ukj]

So which textbook contains the meaning of "meaning"?

Oh, that's recursive! Which is Computer Science's domain of expertise, not the public domain.

We are talking about formal semantics here. What do programs (and computer languages are themselves programs) mean?

Point 0 of Wadler's law.

https://en.wikipedia.org/wiki/Semantics_(computer_science)

If you can type-check it at compile time then it is NOT dynamic dispatch. It's a contextual confusion.

[ukj]

It turns out "dynamic dispatch" is not as well established or as clear as you insist. It means at least one of five things:

0. Dynamic dispatch (as you are using it) 1. Double dispatch 2. Multiple dispatch 3. Predicate dispatch 4. All of the above collectively.

What you thought was a confusing re-definition on my part might have been an ignorance of alternative uses on yours ;)

Java doesn't do 1, 2 or 3.

[detaro]

so you are using a different definition of dynamic dispatch than the rest of the software industry.

[ukj]

I am using a conception (NOT a definition) that is actually dynamic.

If you can type-check your dispatcher at compile time then there is nothing dynamic about it.

Decidable (ahead of time) means your function is fully determined. Something that is fully determined is not dynamic.

It is the conception computer scientists use.