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That's because the code triggering compilation error is using reference. If you use Rc or Arc (which pays runtime cost) there should be no lifetime at all. Alb

by namjh 2y ago

That's because the code triggering compilation error is using reference. If you use Rc or Arc (which pays runtime cost) there should be no lifetime at all. Albeit I admit there somewhat exists a community sentiment like "if you use Rust, you should maximize its zero cost abstraction feature so lifetime is good and generics good", and my (minor) opinion is that, it's not always true to all users of Rust. And the clumsy Arc<Mutex<Something<TheOtherThing>>> makes users feel bad about using runtime cost paid types. Maybe we should introduce easy Rust dialect which transpiles into Rc/Clone everywhere but I doubt it's trivial to transpile.

dmurray 2y ago
> And the clumsy Arc<Mutex<Something<TheOtherThing>>> makes users feel bad about using runtime cost paid types Yeah, this would look worse than any of the "complicated syntax" examples in the blog post. A language should be designed so that the typical case is the easiest to read and write. Syntax for the most common abstractions. Rust forces you to be explicit if you want to do an Arc<Mutex<Box>>>, but lets you inherit lifetimes almost seamlessly. That means it's not idiomatic to do the first, and it is to do the second. Languages with a lot of historical baggage don't follow this pattern: if you want to write idiomatic modern C++ it's going to be uglier and more verbose than you see in K&R. But in Rust's case it's clear what the designers encourage you to do.
- _answ 2y ago
  Simple != idiomatic. It's perfectly idiomatic to `Arc<Mutex<Box>>` in Rust, and it is more complex because it deals with more concerns than a simple reference, namely being thread-safe. Sometimes you need that, sometimes not, but you have to be explicit about it.
  - steveklabnik 2y ago
    There’s no reason to have a Box<T> there, because Arc already boxes.
- cozzyd 2y ago
  Not sure why you'd compare modern C++ to K&R which is a C book. Modern C is in fact less ugly than ancient C due to sugar like compound literals.
  - deleted 2y ago
    [deleted]

by namjh 2y ago

dmurray 2y ago

> And the clumsy Arc<Mutex<Something<TheOtherThing>>> makes users feel bad about using runtime cost paid types Yeah, this would look worse than any of the "complicated syntax" examples in the blog post. A language should be designed so that the typical case is the easiest to read and write. Syntax for the most common abstractions. Rust forces you to be explicit if you want to do an Arc<Mutex<Box>>>, but lets you inherit lifetimes almost seamlessly. That means it's not idiomatic to do the first, and it is to do the second. Languages with a lot of historical baggage don't follow this pattern: if you want to write idiomatic modern C++ it's going to be uglier and more verbose than you see in K&R. But in Rust's case it's clear what the designers encourage you to do.

_answ 2y ago
Simple != idiomatic. It's perfectly idiomatic to `Arc<Mutex<Box>>` in Rust, and it is more complex because it deals with more concerns than a simple reference, namely being thread-safe. Sometimes you need that, sometimes not, but you have to be explicit about it.
- steveklabnik 2y ago
  There’s no reason to have a Box<T> there, because Arc already boxes.
cozzyd 2y ago
Not sure why you'd compare modern C++ to K&R which is a C book. Modern C is in fact less ugly than ancient C due to sugar like compound literals.
- deleted 2y ago
  [deleted]