6 ms·

> Rust isn't really all that hard. You don't find it hard. Many do.

kibwen 4y ago
Yes, Rust is quite different from typical languages thanks to ownership and borrowing. It often takes people several attempts to learn it before their perspective shifts and it finally clicks for them. But this perception of Rust has less to do with Rust being "hard" than it has to do with Rust being "different". To be sure, Rust has hard parts even after you've internalized the differences, but IMO by that point it's not substantially different from mastering the hard parts of other languages (especially other systems languages, none of whom can get away with entirely sweeping the details of the machine under the rug).
nu11ptr 4y ago
I can see how it could be hard for someone used to high level languages and who doesn't care about how memory actually works "under the hood". The secret to learning Rust is really the same as C/C++: you have to learn to think of memory in a low level way -and- learn Rust's safety rules for dealing with that. I think it does take someone very dedicated to the task, more so than is required to learn say Python, for example. However, I find it much more rewarding.
- aussiesnack 4y ago
  I don't think the ownership model, borrowing, references etc are actually particularly difficult. They're well explained in "The Book", even better so in Jim Blandy's "Programming Rust", and at least in principle can be got over in an afternoon. Admittedly it can all knotty with a lot of closures and async etc, but it's certainly not the source of the difficulties for me.
bsder 4y ago
> You don't find it hard. Many do. The question at the end of the day is whether that "hardness" is required or accidental. My gut feel is that Rust does have some accidental complexity--poor support for static/globals, poor support for placement new and alternate allocators, inability to transmute equivalent types well, etc. However, my gut feel is also that a lot of Rust's "difficulty" is the fact that people really don't know how to program C/C++ even remotely correctly, and Rust is simply slapping them in the face with that fact.
- kibwen 4y ago
  *> poor support for static/globals I'll agree with your other things, but discouraging global state is an aspect that reduces ultimate complexity, rather than increasing it. :P
  - sam0x17 4y ago
    global state is often necessary. Abusing it is always possible, but every startup-sized application footprint I've ever been in we eventually have to add an exception to the no-globals linting rule for some very legitimate reason in some specific place. The crate ecosystem (oncecell, lazystatic) lets you completely sidestep this limitation for now anyway before better const behavior eventually gets added to stable
  - jandrewrogers 4y ago
    It increases complexity if the state is intrinsically global. Hardware resources, for example, which are commonly directly managed in systems code, are intrinsically global state. You can't allocate another hard drive or physical network interface. I've seen impressively convoluted code that existed solely to pretend that global state isn't actually global state, because that was seen as bad, even though it behaved exactly like global state.
    - tialaramex 4y ago
      Rust is comfortable with immutable statics. The existence of a global readable Doodad is no problem. For mutable access static Doodad Rust requires unsafe, because you will probably shoot yourself in the foot. Imagine there's a static NetworkIF nic which is immutable. Maybe we can call predicates like nic.up() to find out if this interface is up, or nic.packet_counts() to get some statistics about packets. But it's immutable, so we can't call nic.change_addr() or nic.disable_packet_filters() as those require mutation. If it was mutable we'd need unsafe Rust to try to call those, because doing so means being very careful about who does what and when they do it or we'll get in a mess. Because of "interior mutability" we can have a Rust static which is immutable from a Rust point of view, and thus safe, but where we can get at mutable internals. For example static Mutex<NetworkIF> nic. Now it's protected by a mutex. We can lock the mutex, and thus get mutable access to the NetworkIF, until we release that lock. If somebody else has the lock then we'd block waiting for them to release it. With just mutable globals everywhere and a larger team it's easy to end up with clashes where two subsystems both think they "own" a shared mutable object and treat it accordingly then are surprised that this doesn't consistently do what they expected.
qalmakka 4y ago
The point is, Rust is vastly easier than C++ when you start factoring in the complexity of debugging nasty design choices that comes to bite you in the back and you can't really fix without tearing the whole application apart. Yesterday I was fighting the borrow checker because it wasn't allowing me to pass a reference in an async function. After a while it dawned me that if that thing I was attempting to write would have been accepted, it would have caused a crash in some rare, but not impossible, circumstances. It saved me potentially countless hours of debugging and wrapping my head around the fact that my smart abstraction crashed every once in a while, something that happens to me everyday with C++. Rust is hard, but it's less hard than it's alternatives.
- pjmlp 4y ago
  Dunno, maybe it is Stockholm syndrom from using C++ since 1993, but I definitly find easier to understand template metaprogramming than the upcoming GAT, or the whole Pin and PhatomData stuff.
  - Ygg2 4y ago
    Sure, but you are comparing meta programming facility to a type/lifetime feature that serves as Higher Kinded Type replacement. In Rust same thing holds, macros are easier than GAT I don't get why PhantomData or Pin are that hard to grasp? PhantomData is just a type marker that has no purpose other than help compiler. See https://doc.rust-lang.org/nomicon/phantom-data.html https://doc.rust-lang.org/nomicon/phantom-data.html Pin is a way to create self referential structs, by pinning memory and preventing moves. PhantomPinned is a marker type to ensure your type is not Unpin (it is by default). Unpin it thing that shouldn't be pinned, like bool, i32, etc.
    - qalmakka 4y ago
      > Pin is a way to create self referential structs, by pinning memory and preventing moves. This, exactly. Pin works more or less like a C++ class with a deleted move constructor. Copies may be allowed if clone/copy (aka, the implicit/explicit copy constructor) are defined, but move and RVO are not. Lots of Rust's concepts can often be described in terms of C++'s techniques, but more often than not in C++ it tends to be a hack, while Rust has a formalism for that, like Pin for instance. In C++ you can have moveable self-referencing structs because you can update the self references in the move constructor, but moves in Rust are always memcpy - which is saner IMHO than the whole move constractor and rvalue shenanigans.

Yes, Rust is quite different from typical languages thanks to ownership and borrowing. It often takes people several attempts to learn it before their perspective shifts and it finally clicks for them. But this perception of Rust has less to do with Rust being "hard" than it has to do with Rust being "different". To be sure, Rust has hard parts even after you've internalized the differences, but IMO by that point it's not substantially different from mastering the hard parts of other languages (especially other systems languages, none of whom can get away with entirely sweeping the details of the machine under the rug).

nu11ptr 4y ago

I can see how it could be hard for someone used to high level languages and who doesn't care about how memory actually works "under the hood". The secret to learning Rust is really the same as C/C++: you have to learn to think of memory in a low level way -and- learn Rust's safety rules for dealing with that. I think it does take someone very dedicated to the task, more so than is required to learn say Python, for example. However, I find it much more rewarding.

aussiesnack 4y ago
I don't think the ownership model, borrowing, references etc are actually particularly difficult. They're well explained in "The Book", even better so in Jim Blandy's "Programming Rust", and at least in principle can be got over in an afternoon. Admittedly it can all knotty with a lot of closures and async etc, but it's certainly not the source of the difficulties for me.

bsder 4y ago

> You don't find it hard. Many do. The question at the end of the day is whether that "hardness" is required or accidental. My gut feel is that Rust does have some accidental complexity--poor support for static/globals, poor support for placement new and alternate allocators, inability to transmute equivalent types well, etc. However, my gut feel is also that a lot of Rust's "difficulty" is the fact that people really don't know how to program C/C++ even remotely correctly, and Rust is simply slapping them in the face with that fact.

kibwen 4y ago
*> poor support for static/globals I'll agree with your other things, but discouraging global state is an aspect that reduces ultimate complexity, rather than increasing it. :P
- sam0x17 4y ago
  global state is often necessary. Abusing it is always possible, but every startup-sized application footprint I've ever been in we eventually have to add an exception to the no-globals linting rule for some very legitimate reason in some specific place. The crate ecosystem (oncecell, lazystatic) lets you completely sidestep this limitation for now anyway before better const behavior eventually gets added to stable
- jandrewrogers 4y ago
  It increases complexity if the state is intrinsically global. Hardware resources, for example, which are commonly directly managed in systems code, are intrinsically global state. You can't allocate another hard drive or physical network interface. I've seen impressively convoluted code that existed solely to pretend that global state isn't actually global state, because that was seen as bad, even though it behaved exactly like global state.
  - tialaramex 4y ago
    Rust is comfortable with immutable statics. The existence of a global readable Doodad is no problem. For mutable access static Doodad Rust requires unsafe, because you will probably shoot yourself in the foot. Imagine there's a static NetworkIF nic which is immutable. Maybe we can call predicates like nic.up() to find out if this interface is up, or nic.packet_counts() to get some statistics about packets. But it's immutable, so we can't call nic.change_addr() or nic.disable_packet_filters() as those require mutation. If it was mutable we'd need unsafe Rust to try to call those, because doing so means being very careful about who does what and when they do it or we'll get in a mess. Because of "interior mutability" we can have a Rust static which is immutable from a Rust point of view, and thus safe, but where we can get at mutable internals. For example static Mutex<NetworkIF> nic. Now it's protected by a mutex. We can lock the mutex, and thus get mutable access to the NetworkIF, until we release that lock. If somebody else has the lock then we'd block waiting for them to release it. With just mutable globals everywhere and a larger team it's easy to end up with clashes where two subsystems both think they "own" a shared mutable object and treat it accordingly then are surprised that this doesn't consistently do what they expected.

qalmakka 4y ago

The point is, Rust is vastly easier than C++ when you start factoring in the complexity of debugging nasty design choices that comes to bite you in the back and you can't really fix without tearing the whole application apart. Yesterday I was fighting the borrow checker because it wasn't allowing me to pass a reference in an async function. After a while it dawned me that if that thing I was attempting to write would have been accepted, it would have caused a crash in some rare, but not impossible, circumstances. It saved me potentially countless hours of debugging and wrapping my head around the fact that my smart abstraction crashed every once in a while, something that happens to me everyday with C++. Rust is hard, but it's less hard than it's alternatives.

pjmlp 4y ago
Dunno, maybe it is Stockholm syndrom from using C++ since 1993, but I definitly find easier to understand template metaprogramming than the upcoming GAT, or the whole Pin and PhatomData stuff.
- Ygg2 4y ago
  Sure, but you are comparing meta programming facility to a type/lifetime feature that serves as Higher Kinded Type replacement. In Rust same thing holds, macros are easier than GAT I don't get why PhantomData or Pin are that hard to grasp? PhantomData is just a type marker that has no purpose other than help compiler. See https://doc.rust-lang.org/nomicon/phantom-data.html https://doc.rust-lang.org/nomicon/phantom-data.html Pin is a way to create self referential structs, by pinning memory and preventing moves. PhantomPinned is a marker type to ensure your type is not Unpin (it is by default). Unpin it thing that shouldn't be pinned, like bool, i32, etc.
  - qalmakka 4y ago
    > Pin is a way to create self referential structs, by pinning memory and preventing moves. This, exactly. Pin works more or less like a C++ class with a deleted move constructor. Copies may be allowed if clone/copy (aka, the implicit/explicit copy constructor) are defined, but move and RVO are not. Lots of Rust's concepts can often be described in terms of C++'s techniques, but more often than not in C++ it tends to be a hack, while Rust has a formalism for that, like Pin for instance. In C++ you can have moveable self-referencing structs because you can update the self references in the move constructor, but moves in Rust are always memcpy - which is saner IMHO than the whole move constractor and rvalue shenanigans.