All those statements are correct. The people downvoting you know that too. I don't think anyone has figured out what point you're trying to make, though. Could you spell it out in more detail?
Consider addition. The compiler does type checking, and the JVM actually adds the numbers. Nonetheless, the addition is type checked, and does not represent a weakness of static type checking. How is dynamic dispatch different than this?
You can’t have both static type safety AND dynamic dispatch at the same time and in the same context about the same data.
Choose one. Give up the other. Make a conscious trade off.
The language that you are using is making such trade offs for you - they are implicit in the language design. Best you know what they are because they are meaningful in principle and in practice.
It's pretty clear at this point you don't understand what dynamic dispatch means.
I don't think it's worthwhile for anyone else to argue with you further. C++ and Java both support dynamic dispatch although you deny it.
You've taken up almost a full page of HN arguing with everyone trying to explain it to you. People have pointed you to wikipedia showing you that you're wrong. [1]
ISOCPP of which Bjarne is a director [2] says that C++ supports dynamic dispatch. [3]
And you continue to attempt to argue that everyone on HN, Wikipedia and the creator of the C++ language are all wrong and don't know what dynamic dispatch is.
Your continued insistence is both wrong and a negative impact at this point on hn. Please stop arguing something that numerous people have taken lots of patience and charity in trying every way possible to explain to you and what is clearly factually wrong.
If you're going to reply, please explain why an organization that Bjarne Stroustrup is a director of believes that C++ supports dynamic dispatch.
> It's pretty clear at this point you don't understand what dynamic dispatch means.
Terms in computing are so overloaded that these days I try[0] and never correct anyone on how they use a term. Instead I ask them to define it, and debate off of that definition.
So instead of downvoting this guy for using different terminology - we can ask him what he means and just have a discussion.
[0] alright I don't always succeed but it's an ideal to strive for
"Virtual method tables also only work if dispatching is constrained to a known set of methods, so they can be placed in a simple array built at compile time."
If the vtable is generated at compile and is constrained to a known set of methods then that array is immutable! Calling that "dynamic" is an obvious misnomer!
You are neither charitable nor patient. You are committing the bandwagon fallacy as we speak. You and the other 120 (and counting) angry downvoters ;)
I am using the word "dynamic" to actually mean dynamic!
I am not going to define it. Use your judgment. Dynamic is NOT static.
I am not asking you to "educate me", or to tell me I am right; or wrong.
I am asking you to understand the sort of programming language design I have in mind!
for all expressions e:
if e type checks with type t, then one of the following holds:
- e evaluates to a value v of type t; or
- e does not halt; or
- e hits an "unavoidable error"
like division by 0 or null deref
(what counts as "unavoidable" varies from lang to lang)
Notice anything interesting about this definition? It uses the word "evaluate"! Type soundness is not just a statement about the type checker. It relates type checking to run time (and thus to compilation too). That is, if you muck with Java's runtime or compiler, you can break type soundness, even if you don't change its type system in the slightest.
Consider addition. The compiler does type checking, and the JVM actually adds the numbers. Nonetheless, the addition is type checked, and does not represent a weakness of static type checking. How is dynamic dispatch different than this?