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Right, so you implement them with unsafe. While you can implement doubly linked lists safely with refcounting, you're perfectly free to implement them with unsa

Right, so you implement them with unsafe. While you can implement doubly linked lists safely with refcounting, you're perfectly free to implement them with unsafe code. This is what unsafe code is for, designing low level abstractions with clean API boundaries. (Also I don't see how this is relevant at all)

Animats 10y ago
Right, so you implement them with unsafe. If you need unsafe code for basic operations within the language, something is wrong with the language. This isn't about talking to hardware, or an external library. It's pure Rust code. (Some pointer manipulations can be built from swap as a basic operation. That may work for doubly-linked lists. The other big problem is partially valid arrays, such as vectors with extra space reserved. There's no way to talk about that concept within the language. There could be, but this isn't the place to discuss it.)
- kazagistar 10y ago
  > need unsafe code for basic operations within the language Building custom back-referencing data structures is not a "basic operation" anywhere outside programming classes. Adding significant complexity to rust Rust to make a 2% case marginally safer would be make the language worse. As long as the vast majority of code is not unsafe, then it achieves its goal.
- Manishearth 10y ago
  I have been writing Rust code for almost three years now. I have helped design a low level data structure exactly twice. In both cases, this was a highly custom concurrent data structure, which would have been even harder to get right in C++ or some other language. If you need a regular run-of-the-mill datastructure it will exist in the stdlib or crates ecosystem. This is not a "basic task". Just because schools teach it early does not make it a "basic task". It's a task that needs to be done at some point, but doing it once and making it part of the stdlib or a crate is all that is necessary. It has become a "basic task" in C++ because it's easy enough to do that you don't need to reach for the stdlib, but that doesn't mean that it's necessary to have a bespoke implementation of a DLL that often in C++; usually the stdlib one will do. The same "too many lists" book you linked to explains why DLLs are niche datastructures on the first page (singly linked lists can be implemented safely in Rust, though they can be somewhat niche too).

Animats 10y ago

Right, so you implement them with unsafe. If you need unsafe code for basic operations within the language, something is wrong with the language. This isn't about talking to hardware, or an external library. It's pure Rust code. (Some pointer manipulations can be built from swap as a basic operation. That may work for doubly-linked lists. The other big problem is partially valid arrays, such as vectors with extra space reserved. There's no way to talk about that concept within the language. There could be, but this isn't the place to discuss it.)

kazagistar 10y ago
> need unsafe code for basic operations within the language Building custom back-referencing data structures is not a "basic operation" anywhere outside programming classes. Adding significant complexity to rust Rust to make a 2% case marginally safer would be make the language worse. As long as the vast majority of code is not unsafe, then it achieves its goal.
Manishearth 10y ago
I have been writing Rust code for almost three years now. I have helped design a low level data structure exactly twice. In both cases, this was a highly custom concurrent data structure, which would have been even harder to get right in C++ or some other language. If you need a regular run-of-the-mill datastructure it will exist in the stdlib or crates ecosystem. This is not a "basic task". Just because schools teach it early does not make it a "basic task". It's a task that needs to be done at some point, but doing it once and making it part of the stdlib or a crate is all that is necessary. It has become a "basic task" in C++ because it's easy enough to do that you don't need to reach for the stdlib, but that doesn't mean that it's necessary to have a bespoke implementation of a DLL that often in C++; usually the stdlib one will do. The same "too many lists" book you linked to explains why DLLs are niche datastructures on the first page (singly linked lists can be implemented safely in Rust, though they can be somewhat niche too).