Comment by darpa_escapee | Hacker News Reader

Comment by darpa_escapee | Hacker News Reader

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Dart is a nice statically typed and compiled C-style language. If you have experience with another such language, it will feel like you already know Dart. The language compliments Flutter well, and the Flutter SDK makes it simple and easy to rapidly build a functional mobile app.

Lack of certain features, like reflection, in mobile Dart creates a rift in packages you can utilize in a Flutter app. There are a few warts in the type system, mainly around generics, and little things like the lack of union types and type aliasing.

There are also a few outstanding bugs that you might run into, which have had relatively long life since they were identified. The Dart team seems to be reluctant to add new features.

Also, managing state in Flutter is a little unclear: documents and videos from Google recommend four different ways to do so: explicitly calling setState(), Streams with StreamBuilder, scoped_model and the various third-party Dart/Flutter Flux implementations.

It definitely beats native development.

Language with "dynamic" type can't be called "statically typed".

Is C# statically typed?

I don't know.

Really happy to see this absolutely honest and neutral answer downvoted. It says a lot about the level of my opponents.

It says a lot that you consider folks you're having a conversation with "opponents".

Anybody who is arguing with you is your opponent. It's not so dramatic word :)

Yes, it is.

Most languages I can think of have this type, from void* to dyn to bounding by the root of the type hierarchy. Not all languages. However, what is c, c++, java, rust, go, if not statically typed? Ambiguously typed? Seems like not a useful distinction to make.

I argue static typing is the ability to static type up to 100% of a program, not the exclusion of a dynamic type.

Rust doesn't have such type. And type annotations in Dart are optional - when programmers are not obliged to use them, guess what will happen? They do NOT use them. People are lazy.

Dart's types exist only on compilation step. You can try to use "strong mode" in theory, in practice you will never compile it with third-party libraries.

Rust has both raw void* pointers (within unsafe code) and the safe std::any::Any trait: https://doc.rust-lang.org/std/any/trait.Any.html

Trait is not a type, Any is just a custom trait. Types: https://doc.rust-lang.org/book/second-edition/ch03-02-data-t... You can create trait with name "Magic" or "Fuck" and it will not mean anything. Pointers is not a type also.

Pointers are certainly types in Rust, and although it's of course true that the Any trait is not itself a type, a reference to an Any trait (which is what you'd actually pass around) is a type.

Well, you can repeat it many times but it will not become true. I gave you link to the list of Rust types. Pointers are pointers, not types. Traits can have any name, their names mean nothing.

https://doc.rust-lang.org/book/first-edition/raw-pointers.ht...

    *const u32

(for example) is a clearly a Rust type -- a const pointer to an unsigned 32-bit integer, analogous to

    const uint32_t *p

in C/C++.

I'm not sure what you mean about trait names. The purpose of the Any trait is to make it possible to pass around values of any type and dynamically downcast them, as the documentation indicates. That is a safe analogue of casting a void pointer to another type.

To be dynamic, "Any" should be able to represent literally ANY type. As you can find, Any is a reflection-wise trait to work with static types. It's not something what you can use when you don't know type and language will dynamically convert it. You can't write

    fn example(foo: Any) -> u32 {
        foo+55
    }

as you CAN do in dynamic languages. Do you understand me now? Or we will keep talking about unsafe extra special types?

Please remember there's a genuine human on the other end, trying to have a respectful conversation with you.

Or there is a person who is trying to prove his offtopic point by some pedantic interruptions, which are far from the main idea of discussion.

You can do that if you change it to &Any and then downcast. See the docs for examples. If the issue is that you have to downcast, then your initial claim that Rust lacks void pointers was irrelevant even if true, since you also have to downcast a void pointer in C before you can perform operations on the type that it's actually pointing to.

> If the issue is that you have to downcast

It's the difference between dynamic language and language with synthetic type for reflections.

You can't downcast it to anything you want, it returns an Option, void pointers in C are not certainly the same, it's unsafe.

I know. That's why I said it's "a safe analogue of casting a void pointer to another type".

Ok, type bound. You can still easily pass around data whose type is not concretely defined at the compilation step. Unless you’re arguing that the dynamic type is actually static, in which case this whole conversation seems semantically pointless.

2 hours ago I answered it already. If you're another person who wants to convince me that Rust has same thing as Dart's "dynamic" type, then please make my code example to compile (without modifications, for literally ANY type, as in Dart) and I will say I was wrong.

Dart type or rust type? They refer to different things, which is the source of the confusion, but they're both strongly typed.

In any case, you're moving the goal post from "concrete type at compile time" to "can represent any type", which is inherently going to be specific to how the language defines types. This is not an especially useful type of dynamic representation so I'm not sure why it would be desirable.

There is no confusion. Rust doesn't have dynamic type and Dart does. That's it.

Any talks about special traits in Rust are offtopic, while code I wrote as example can't be compiled in Rust and can perfectly work in Dart.

I wasn't trying to argue about words or terms, I was trying to say the gist: Dart has dynamic type, so you can send to your function any type and this function will just use it, without any downcasting - language will take care about it; and Rust doesn't have such type: you can't even compile code which is trying to work with variables like you can do in dynamic languages.

But then all of that useless arguing... It's really funny when I see how people are trying to prove that Rust has same dynamic type as Dart. The very nature of these languages is different.

A pointer is absolutely a type in rust.

let i: u32 = 1;

let p_imm: const u32 = &i;

Look at the const u32 in the type position.

The rust book even refers to const and mut pointers as types.

const and mut are not types, it's modifiers of mutability. On both lines type is u32z

The asterisks in leshow's comment are being lost in the formatting, since HN uses them for italicization. So the last line, for example, is:

    The rust book even refers to *const and *mut pointers as types.

I really can't believe how stupid people can be to say "const" is a type. Even if Klabnik will say it into my face it will not be true, I don't care about the book he wrote.

leshow said that

    *const u32

is a type, not that 'const' is a type. HN's formatting removed the asterisk, as it uses asterkisks for italicization.

The asterisk was formatted out. Read the book, they are types.

So you can write "let x:const = 5"? if "const" is a type.

You were just told the formatting removed the asterisk. const isn't a type, but a const pointer is, so is a mut pointer. It says so in the book AND it's in the position of a type in the code. What other information do you need to convince you that you're wrong?

> And type annotations in Dart are optional - when programmers are not obliged to use them, guess what will happen?

The type system will infer a static type based on the type of the initializer.

In some cases, inference may fail to infer a type. Right now, that can silently give you dynamic, but there's a flag to make that an error. I expect before too long that will be the default behavior.

Dart isn’t statically typed, at least not in the times i’ve used it; it’s gradually typed.

It was optionally typed. Dart 2 is statically typed.

If you have a well-thought out argument, and not a quippy one-liner, I'd earnestly like to hear it.

Dart's developers think otherwise[1]:

> Q. Is Dart a statically typed language?

> Yes, Dart 2 is statically typed. For more information, see Dart’s Type System.

> With its combination of static and runtime checks, Dart has a sound type system, which guarantees that an expression of one type cannot produce a value of another type. No surprises!

> Even with type-safe Dart, you can annotate any variable with dynamic if you need the flexibility of a dynamic language. The dynamic type itself is static, but can contain any type at runtime. Of course, that removes many of the benefits of a type-safe language for that variable.

[1] https://www.dartlang.org/faq#q-is-dart-a-statically-typed-la...

> With its combination of static and runtime checks

Do you personally use it? That "strong mode" is a theory-only thing, it doesn't work with any real code, only with code you wrote without real third-party libraries.

You are, at best, confusing Dart 2 with Dart 1; strong mode was one of several Dart 1 modes, but, yes, it's possible to run into problems because dependencies weren't designed for it.

There is no option in Dart 2; everything is the equivalent of strong mode, which eliminates ecosystem problems.

I mentioned I've only tried Dart 1.x. Glad to hear it's changed in Dart 2.

> only with code you wrote without real third-party libraries.

Your claim was true several years ago, but since then the entire ecosystem has migrated onto the new strict type system. It was a monumental amount of work, but, thanks to lots of effort from our users, we're there.

Aside from a small number of more-or-less dead packages, you should be able to use any third-party Dart packages you want while still using the new type system.

C#, Scala, Kotlin, TypeScript, et. al have a dynamic type. As long as every type isn't dynamic, I think it's reasonable to claim you have static types.

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