4 ms·

What things are hideous about it and what would you rather it look like?

by dmm 2y ago

andrewmcwatters 2y ago
[flagged]
- kranuckle 2y ago
  [dead]
flohofwoe 2y ago
That video snippet which was posted by that former Rust/Linux maintainer has an excellent example: https://www.youtube.com/watch?t=1529&v=WiPp9YEBV0Q&feature=youtu.be https://www.youtube.com/watch?t=1529&v=WiPp9YEBV0Q&feature=y... The return type of that get_or_create_inode() function is: Result<Either<ARef<INode<T>>, inode::New<T>>> I'd say that's a pretty good example for 'hideous'. It looks like some of the worst C++ code I've seen and then quickly tried to forget. If stuff like this ends up in the Linux kernel I would be pissed too as a Linux kernel greybeard.
- steveklabnik 2y ago
  I agree that it could maybe use some new types, but it also does kinda get to the heart of this: I’ve never used this kernel API before, but I can say “oh, this function may error out, but if it doesn’t, it gives me either a new inode or a reference (I’m assuming that’s what ARef is) to an existing one. That’s a lot of valuable information, at a glance.
  - flohofwoe 2y ago
    > That’s a lot of valuable information, at a glance ...if you know how to decode it. That example looks like one of those C++ SFINAE hacks, e.g. trying to bend the template/generics syntax beyond what it was designed for. If Rust APIs want to go that way (of overly expressive strong typing) then Rust really should offer a better syntax for describing such types. But it's not even clear to me if such strongly typed APIs are even a good idea. From my experience in C++ and (especially) Typescript with similar APIs, it's a PITA to work with in real world projects, and on both sides of the API.
    - steveklabnik 2y ago
      I mean, it’s very straightforward generics. There’s just nesting, each of these types has one or two parameters and that’s it. I’m not sure there’s a simpler way of communicating the same thing. But I also think that I wouldn’t design an API that works like this in Rust natively; this is adapting a signature from C rather than doing the API you’d want if you were creating something from whole cloth. I also believe that static types are very different based on the language; I’d rather write Ruby than Java, but I’d rather write Rust than Ruby. More advanced type systems tend to actually pull their weight, whereas simpler ones don’t give enough juice for the squeeze, IMHO.
      - flohofwoe 2y ago
        IMHO there's a pretty wide range between static weak typing and static strong typing even within a single language. Going too far into either extreme has more downsides than upsides - yes, strongly typed code will be more correct because the types might catch usage 'logic errors' during compilation, but also harder to maintain when requirements change (because strong types tend to creep into every little corner of a code base - and they are extremely rigid by design making the code which uses them also very rigid). My goto example where I burned myself in the past is splitting a vec4 into point and vector types. It totally makes sense from a theoretical design pov (e.g. `point + point` would be illegal, while `point + vector` or `vector + vector` are allowed). But in reality such code is awkward to work with for many little reasons, and the enforced correctness pretty much never catches bugs, it just adds pointless busy work when the code needs to change.
        still_grokking 2y ago
        I agree that something like "over-typing" exists. But where it starts is imho very context dependent. For the lowest level (e.g. an OS) you really want an extremely strict regime. Bugs are "simply not allowed"… For application level code I think it depends. Nobody would finish anything if the requirement would be to formally verify all your code. The other thing is: How far you can get before "over-typing" starts is also dependent on the language and how powerful it's type inference system is. Rust is quite weak in this regard. In a language where the compiler can pass context for you one can have very strong guaranties without making working with the code too awkward. Of course, changing the code will need work. But that's the whole point of type systems: If you change something the compiler will tell you any places where something needs repair. In less strongly typed languages you can just pray that your tests are good enough to cover the changes. In case of changes a good compiler will even rewrite the trivial cases for you if you ask, and just leave what really needs human oversight. But such automatic rewriting (with the guaranty that nothing went wrong!) works only if you had very strong types in the first place.
- kranuckle 2y ago
  [dead]
- commodoreboxer 2y ago
  Maybe it's because I'm working a lot with V8, but that looks quite a lot like most C++ generics I've been looking at lately. Especially when working with concepts, it's easy to end up 5 or more nested angle brackets in.
  - flohofwoe 2y ago
    Yeah, but is that a good thing? Complex template magic is hardly one of the good parts of modern C++.
    - lifthrasiir 2y ago
      Rust generics are much underpowered than C++ templates in order to make them an integral part of type system. Many practical C++ programmers avoid excessive template magics for that reason and also for simplicity, and Rust's restriction is essentially its codification.
    - still_grokking 2y ago
      But it's not template magic. Not even something close. It's just nested generic types. How would you otherwise express all the constrains in a type?
- iknowstuff 2y ago
  enum ReceivedINode<T> { Existing(ARef<INode<T>) New(inode::New<T>) } fn get(..) -> Result<ReceivedINode<T>> Calm down with the bikeshedding. It’s just a complex C API and they wanted to convey the semantics concisely.
- still_grokking 2y ago
  I didn't watch any other talks of this conference, but it looks to me as part of the issue here was that the presenter didn't explain basic (ML) types upfront. Maybe they did in other talks earlier, IDK. If you never seen such types before it may look intimidating. But if you ever seen any ML style language the type of said function looks actually very ordinary. It does not use any really more complex concepts, it's just regular nested generic types. Pretty standard stuff. In Rust you could also have things like: fn foo<'a, T, U, V, W>(a: &'a T, b: U, c: V, d: W) where T: MyTrait<U> + Debug + 'a, U: Debug + Hash, V: SomeOtherTrait<V> + Debug + std::marker::Copy, W: Box<dyn Fn(V) -> U> + Debug, { todo!("Just a demo"); } That's indeed much more involved, even it doesn't use any deeply nested wrapper types. But I think nobody would force such complex signatures on API end-users. (Even there is of course also no magic going on. It's just the quite quite expressive type language in Rust).

What things are hideous about it and what would you rather it look like?

by dmm 2y ago

What things are hideous about it and what would you rather it look like?

andrewmcwatters 2y ago

[flagged]

kranuckle 2y ago
[dead]

flohofwoe 2y ago

That video snippet which was posted by that former Rust/Linux maintainer has an excellent example: https://www.youtube.com/watch?t=1529&v=WiPp9YEBV0Q&feature=youtu.be https://www.youtube.com/watch?t=1529&v=WiPp9YEBV0Q&feature=y... The return type of that get_or_create_inode() function is: Result<Either<ARef<INode<T>>, inode::New<T>>> I'd say that's a pretty good example for 'hideous'. It looks like some of the worst C++ code I've seen and then quickly tried to forget. If stuff like this ends up in the Linux kernel I would be pissed too as a Linux kernel greybeard.

steveklabnik 2y ago
I agree that it could maybe use some new types, but it also does kinda get to the heart of this: I’ve never used this kernel API before, but I can say “oh, this function may error out, but if it doesn’t, it gives me either a new inode or a reference (I’m assuming that’s what ARef is) to an existing one. That’s a lot of valuable information, at a glance.
- flohofwoe 2y ago
  > That’s a lot of valuable information, at a glance ...if you know how to decode it. That example looks like one of those C++ SFINAE hacks, e.g. trying to bend the template/generics syntax beyond what it was designed for. If Rust APIs want to go that way (of overly expressive strong typing) then Rust really should offer a better syntax for describing such types. But it's not even clear to me if such strongly typed APIs are even a good idea. From my experience in C++ and (especially) Typescript with similar APIs, it's a PITA to work with in real world projects, and on both sides of the API.
  - steveklabnik 2y ago
    I mean, it’s very straightforward generics. There’s just nesting, each of these types has one or two parameters and that’s it. I’m not sure there’s a simpler way of communicating the same thing. But I also think that I wouldn’t design an API that works like this in Rust natively; this is adapting a signature from C rather than doing the API you’d want if you were creating something from whole cloth. I also believe that static types are very different based on the language; I’d rather write Ruby than Java, but I’d rather write Rust than Ruby. More advanced type systems tend to actually pull their weight, whereas simpler ones don’t give enough juice for the squeeze, IMHO.
    - flohofwoe 2y ago
      IMHO there's a pretty wide range between static weak typing and static strong typing even within a single language. Going too far into either extreme has more downsides than upsides - yes, strongly typed code will be more correct because the types might catch usage 'logic errors' during compilation, but also harder to maintain when requirements change (because strong types tend to creep into every little corner of a code base - and they are extremely rigid by design making the code which uses them also very rigid). My goto example where I burned myself in the past is splitting a vec4 into point and vector types. It totally makes sense from a theoretical design pov (e.g. `point + point` would be illegal, while `point + vector` or `vector + vector` are allowed). But in reality such code is awkward to work with for many little reasons, and the enforced correctness pretty much never catches bugs, it just adds pointless busy work when the code needs to change.
      - still_grokking 2y ago
        I agree that something like "over-typing" exists. But where it starts is imho very context dependent. For the lowest level (e.g. an OS) you really want an extremely strict regime. Bugs are "simply not allowed"… For application level code I think it depends. Nobody would finish anything if the requirement would be to formally verify all your code. The other thing is: How far you can get before "over-typing" starts is also dependent on the language and how powerful it's type inference system is. Rust is quite weak in this regard. In a language where the compiler can pass context for you one can have very strong guaranties without making working with the code too awkward. Of course, changing the code will need work. But that's the whole point of type systems: If you change something the compiler will tell you any places where something needs repair. In less strongly typed languages you can just pray that your tests are good enough to cover the changes. In case of changes a good compiler will even rewrite the trivial cases for you if you ask, and just leave what really needs human oversight. But such automatic rewriting (with the guaranty that nothing went wrong!) works only if you had very strong types in the first place.
kranuckle 2y ago
[dead]
commodoreboxer 2y ago
Maybe it's because I'm working a lot with V8, but that looks quite a lot like most C++ generics I've been looking at lately. Especially when working with concepts, it's easy to end up 5 or more nested angle brackets in.
- flohofwoe 2y ago
  Yeah, but is that a good thing? Complex template magic is hardly one of the good parts of modern C++.
  - lifthrasiir 2y ago
    Rust generics are much underpowered than C++ templates in order to make them an integral part of type system. Many practical C++ programmers avoid excessive template magics for that reason and also for simplicity, and Rust's restriction is essentially its codification.
  - still_grokking 2y ago
    But it's not template magic. Not even something close. It's just nested generic types. How would you otherwise express all the constrains in a type?
iknowstuff 2y ago
enum ReceivedINode<T> { Existing(ARef<INode<T>) New(inode::New<T>) } fn get(..) -> Result<ReceivedINode<T>> Calm down with the bikeshedding. It’s just a complex C API and they wanted to convey the semantics concisely.
still_grokking 2y ago
I didn't watch any other talks of this conference, but it looks to me as part of the issue here was that the presenter didn't explain basic (ML) types upfront. Maybe they did in other talks earlier, IDK. If you never seen such types before it may look intimidating. But if you ever seen any ML style language the type of said function looks actually very ordinary. It does not use any really more complex concepts, it's just regular nested generic types. Pretty standard stuff. In Rust you could also have things like: fn foo<'a, T, U, V, W>(a: &'a T, b: U, c: V, d: W) where T: MyTrait<U> + Debug + 'a, U: Debug + Hash, V: SomeOtherTrait<V> + Debug + std::marker::Copy, W: Box<dyn Fn(V) -> U> + Debug, { todo!("Just a demo"); } That's indeed much more involved, even it doesn't use any deeply nested wrapper types. But I think nobody would force such complex signatures on API end-users. (Even there is of course also no magic going on. It's just the quite quite expressive type language in Rust).