Learn Rust with entirely too many linked lists (2019) • Hacker News Board

Re: Learn Rust with entirely too many linked lists (2019)

#11

Post by ajross » Sat, Feb 22, 2020, 3:42 PM UTC

roblabla wrote: post #9

ajross wrote: post #2

> Mumble mumble kernel embedded something something intrusive. And this is why kernel/embedded/something/something developers don't take Rust as seriously as you want them to. You can't simultaneously declare your language the best choice for system software development and treat the long-evolved patterns of those paradigms as a joke. There are very good reasons for intrusive data structures, not least of which being…

The actual context of your quote: > Just so we're totally 100% clear: I hate linked lists. With a passion. Linked lists are terrible data structures. Now of course there's several great use cases for a linked list: > > - You're writing a kernel/embedded thing and want to use an intrusive list. So I’ve got no clue what you’re railing about. The project specifically acknowledges that there is a need in kerneldev for th…

(Had to edit in a quote to what I was replying to because you fixed the original):

> The actual context of your fake quote:

Good grief, that was a verbatim quote! Here's a link to the exact text I quoted:

https://rust-unofficial.github.io/too-many-lists/#mumble-mum...

Re: Learn Rust with entirely too many linked lists (2019)

#12

Post by jasondclinton » Sat, Feb 22, 2020, 3:43 PM UTC

I went through this a few years ago for fun. It's a great guided tour of the compiler errors when working with complex memory safety needs. The most important thing to know about these is that you would almost certainly never do these in a real project: lists are in `std` but even then the vast majority of cases should use `Vec`.

Re: Learn Rust with entirely too many linked lists (2019)

#13

Post by jasondclinton » Sat, Feb 22, 2020, 3:48 PM UTC

ajross wrote: post #2

> Mumble mumble kernel embedded something something intrusive. And this is why kernel/embedded/something/something developers don't take Rust as seriously as you want them to. You can't simultaneously declare your language the best choice for system software development and treat the long-evolved patterns of those paradigms as a joke. There are very good reasons for intrusive data structures, not least of which being…

https://github.com/Amanieu/intrusive-rs implements what you're looking for with no heap. There's no need to flame or misrepresent what the book says (no one said embedded was a joke). The Rust embedded community is strong.

Re: Learn Rust with entirely too many linked lists (2019)

#14

Post by jasondclinton » Sat, Feb 22, 2020, 3:49 PM UTC

redrobein wrote: post #8

robbyt wrote: post #5

Earlier quoted context omitted.

To explain what I think this comment means. When working on embedded systems, you can interact with hardware devices by writing directly to specially mapped memory areas. E.g., if you want to write text to a small screen, the kernel driver gives you a memory region that you write bytes to, and they're shown on the screen immediately, without requiring the CPU.

> To explain what I think this comment means. When working on embedded systems, you can interact with hardware devices by writing directly to specially mapped memory areas. And why can't you do this in rust?

You can. Rust allows full memory addressing.

Re: Learn Rust with entirely too many linked lists (2019)

#15

Post by ajross » Sat, Feb 22, 2020, 3:54 PM UTC

jasondclinton wrote: post #13

ajross wrote: post #2

> Mumble mumble kernel embedded something something intrusive. And this is why kernel/embedded/something/something developers don't take Rust as seriously as you want them to. You can't simultaneously declare your language the best choice for system software development and treat the long-evolved patterns of those paradigms as a joke. There are very good reasons for intrusive data structures, not least of which being…

https://github.com/Amanieu/intrusive-rs implements what you're looking for with no heap. There's no need to flame or misrepresent what the book says (no one said embedded was a joke). The Rust embedded community is strong.

You're like the sixth person to argue I'm somehow "misrepresenting" what is being said in this book? I'm quoting it directly. The "flame" is in the original, and I'm responding to it.

Take it out. It's bad.

Re: Learn Rust with entirely too many linked lists (2019)

#16

Post by _bxg1 » Sat, Feb 22, 2020, 3:56 PM UTC

When I was first getting started with Rust this tutorial was eye-opening. It gave me a clear view into the somewhat impenetrable world of working with Boxes (pointers to the heap) directly, in the context of the borrow-checker.

It also convinced me that you usually just want to use the standard library data structures if you can :P

Re: Learn Rust with entirely too many linked lists (2019)

#17

Post by lawn » Sat, Feb 22, 2020, 3:56 PM UTC

redrobein wrote: post #8

robbyt wrote: post #5

Earlier quoted context omitted.

To explain what I think this comment means. When working on embedded systems, you can interact with hardware devices by writing directly to specially mapped memory areas. E.g., if you want to write text to a small screen, the kernel driver gives you a memory region that you write bytes to, and they're shown on the screen immediately, without requiring the CPU.

> To explain what I think this comment means. When working on embedded systems, you can interact with hardware devices by writing directly to specially mapped memory areas. And why can't you do this in rust?

There's nothing to prevent you from doing this, although you may have to wrap it in an unsafe block.

Re: Learn Rust with entirely too many linked lists (2019)

#18

Post by steveklabnik » Sat, Feb 22, 2020, 3:56 PM UTC

ajross wrote: post #10

steveklabnik wrote: post #7

Earlier quoted context omitted.

It explicitly says that there are good use cases, just that they’re very rare.

It does not. Maybe somewhere else it does. That section, verbatim, says: It's niche. You're talking about a situation where you're not even using your language's runtime. Is that not a red flag that you're doing something strange? It's also wildly unsafe. But sure. Build your awesome zero-allocation lists on the stack. And this is (1) wildly mistating the requirements and (2) deeply offensive to those of us who work…

> It's a fine data structure with several great use cases, but those use cases are exceptional, not common.

Re: Learn Rust with entirely too many linked lists (2019)

#19

Post by throwaway17_17 » Sat, Feb 22, 2020, 3:59 PM UTC

roblabla wrote: post #9

ajross wrote: post #2

> Mumble mumble kernel embedded something something intrusive. And this is why kernel/embedded/something/something developers don't take Rust as seriously as you want them to. You can't simultaneously declare your language the best choice for system software development and treat the long-evolved patterns of those paradigms as a joke. There are very good reasons for intrusive data structures, not least of which being…

The actual context of your quote: > Just so we're totally 100% clear: I hate linked lists. With a passion. Linked lists are terrible data structures. Now of course there's several great use cases for a linked list: > > - You're writing a kernel/embedded thing and want to use an intrusive list. So I’ve got no clue what you’re railing about. The project specifically acknowledges that there is a need in kerneldev for th…

The quote that the GP is talking about is included below, which copy/pasted from the project page, and the Mumble mumble line is the heading for a paragraph:

‘’’Mumble mumble kernel embedded something something intrusive.

It's niche. You're talking about a situation where you're not even using your language's runtime. Is that not a red flag that you're doing something strange?

It's also wildly unsafe.’’’

Also, prior to this author claims the following, where the first line also a section heading:

‘’’ I can't afford amortization

You've already entered a pretty niche space’’’

These fiat rulings based on one an authors generalization of what is ‘niche’ are what I assume GP was commenting on. These are the kinds of dismissals that some developers take issue with, as GP states.

Re: Learn Rust with entirely too many linked lists (2019)

#20

Post by saagarjha » Sat, Feb 22, 2020, 4:07 PM UTC

fortran77 wrote: post #6

ajross wrote: post #2

> Mumble mumble kernel embedded something something intrusive. And this is why kernel/embedded/something/something developers don't take Rust as seriously as you want them to. You can't simultaneously declare your language the best choice for system software development and treat the long-evolved patterns of those paradigms as a joke. There are very good reasons for intrusive data structures, not least of which being…

My feelings, too. I do both embedded programming (in C/C++ and CUDA) and Erlang programming for a living. Erlang, too, doesn't let you (easily) write your own linked list structures, etc. But for embedded programming with tight memory or performance constraints these data structures are essential so we use C++ or even C. They're well understood and the implementations have simple, elegant solutions. For "safety" when…

Rust gives you just as much control as C when you need it.