That's true, but I just have to ask: so what? I, for one, don't subscribe to the theory that popularity equals quality. Although both C and C++ are immensely popular in terms of code written in them that doesn't mean they're the last word in language design.
> No other languages today can compare to them, and the ones that try still depend very heavily on one or both.
I don't understand what you mean by "compare to them". If you mean in terms of features - sure there are languages more advanced. If you mean in terms of popularity then I can only say I find such comparisons meaningless.
> Now, if we could reliably implement class-based OO systems comparable to,
> or even better than, those found in Java, C#, C++, Python, Ruby, and Smalltalk,
> for example, then maybe we could say prototype-based OO is more expressive.
We can do this (modulo "reliably", which I don't understand what you mean by) and that's the problem. You yourself explain this:
> However, all we end up with are multiple half-assed
That's exactly the case. Java, C++, Python and Ruby are extremely incompatible with each other. No wonder that JS implementations of ideas taken from those languages are still incompatible - although less so than originals between themselves. It's also not that strange that they are incomplete - given that everything you'd like to do in class-based system you can do with prototypes there is simply no need for frameworks being complete.
Can you post a few examples of what is possible in Java and not possible in JavaScript?
Also remember that language designers can alter syntax to better support their systems, so we need to exclude syntax from comparison.
> It's much more effective to implement prototype-based OO systems using class-based OO languages.
I don't know if it's impossible, but your examples are flawed. Of course you can write any language in any language, like JS VMs are. But that's completely different matter, I was talking about using the language itself in a prototype based manner. I suspect that, due to static and low-level nature of classes in C++ it's completely, utterly impossible to replicate JS object system inside C++. That you can write interpreter that implements this system is obvious and not interesting at all.
As a counter example, in Python you could, with careful use of metaclasses and implementation details of classes and objects create objects whose methods lookup order and semantics of would be the same or close to those of prototype based JS - in the language itself.
=======
Your arguments fail to prove that prototype based-ness somehow fails. It does not, in itself, fail in any way. As I wrote above, show what can be done with classes (single inheritance model) that cannot be replicated using JS or better IO prototype semantics - that would be convincing. The fact that JavaScript development is a mess - I won't deny it - proves nothing about prototypes and only a bit about JS.
By the way, have you tried Haskell, OCaml or F# and Erlang?
That's true, but I just have to ask: so what? I, for one, don't subscribe to the theory that popularity equals quality. Although both C and C++ are immensely popular in terms of code written in them that doesn't mean they're the last word in language design.
> No other languages today can compare to them, and the ones that try still depend very heavily on one or both.
I don't understand what you mean by "compare to them". If you mean in terms of features - sure there are languages more advanced. If you mean in terms of popularity then I can only say I find such comparisons meaningless.
> Now, if we could reliably implement class-based OO systems comparable to, > or even better than, those found in Java, C#, C++, Python, Ruby, and Smalltalk, > for example, then maybe we could say prototype-based OO is more expressive.
We can do this (modulo "reliably", which I don't understand what you mean by) and that's the problem. You yourself explain this:
> However, all we end up with are multiple half-assed
That's exactly the case. Java, C++, Python and Ruby are extremely incompatible with each other. No wonder that JS implementations of ideas taken from those languages are still incompatible - although less so than originals between themselves. It's also not that strange that they are incomplete - given that everything you'd like to do in class-based system you can do with prototypes there is simply no need for frameworks being complete.
Can you post a few examples of what is possible in Java and not possible in JavaScript?
Also remember that language designers can alter syntax to better support their systems, so we need to exclude syntax from comparison.
> It's much more effective to implement prototype-based OO systems using class-based OO languages.
I don't know if it's impossible, but your examples are flawed. Of course you can write any language in any language, like JS VMs are. But that's completely different matter, I was talking about using the language itself in a prototype based manner. I suspect that, due to static and low-level nature of classes in C++ it's completely, utterly impossible to replicate JS object system inside C++. That you can write interpreter that implements this system is obvious and not interesting at all.
As a counter example, in Python you could, with careful use of metaclasses and implementation details of classes and objects create objects whose methods lookup order and semantics of would be the same or close to those of prototype based JS - in the language itself.
=======
Your arguments fail to prove that prototype based-ness somehow fails. It does not, in itself, fail in any way. As I wrote above, show what can be done with classes (single inheritance model) that cannot be replicated using JS or better IO prototype semantics - that would be convincing. The fact that JavaScript development is a mess - I won't deny it - proves nothing about prototypes and only a bit about JS.
By the way, have you tried Haskell, OCaml or F# and Erlang?