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> But I'm not sure I've heard of anyone running into that limitation in practice. Algorithms processing trees and graphs are everywhere, both in practice and i

> But I'm not sure I've heard of anyone running into that limitation in practice. Algorithms processing trees and graphs are everywhere, both in practice and in CS theory. Both are hard to implement in Rust and/or slow and/or require complex unsafe code. Here’s an example for trees, as you see all 3 approaches are far from ideal: https://github.com/SimonSapin/rust-forest https://github.com/SimonSapin/rust-forest Another thing, because of that ownership thing, in Rust it’s harder to compose data structures. For example, here’s 1300 lines of code implementing hashmap + linked list combination: https://docs.rs/linked-hash-map/0.4.2/src/linked_hash_map/lib.rs.html https://docs.rs/linked-hash-map/0.4.2/src/linked_hash_map/li... Sure, that particular collection is already in Rust’s standard library. However, quite often I need to compose standard library containers my own way. In Rust, that’s either a lot of complex unsafe code like that LinkedHashMap, or performance sacrifice (e.g. switching from pointers to index in a vector, or ref.counting).

oconnor663 9y ago
I'd heard about the graph issue, but I don't know much about it. Is the main takeaway that GC makes managing trees/graphs a lot easier? If we were talking about C++ instead of Rust, what extra options would there be?
- Const-me 9y ago
  > Is the main takeaway that GC makes managing trees/graphs a lot easier? It does indeed. But raw pointers in C or C++ also make it easier than Rust. Sure, it’s very easy to screw things up leaking and/or corrupting memory. But it still quite possible to implement correctly, I did that more than once. Technically, you can usually do the same in Rust with unsafe pointers. Like the developers did to implement that LinkedHashMap for the Rust’s standard library. However, C++ is just better for writing unsafe code like this. After all, it evolved for decades being an unsafe language. Over that time, huge amount of stuff were implemented in the language (STL, esp. the checked version), runtime (debug heap), standalone tools (vtune, valgrind), and even OS (windbg) to help people implement e.g. graphs without leaking memory or exposing dangling pointers.

oconnor663 9y ago

I'd heard about the graph issue, but I don't know much about it. Is the main takeaway that GC makes managing trees/graphs a lot easier? If we were talking about C++ instead of Rust, what extra options would there be?

Const-me 9y ago
> Is the main takeaway that GC makes managing trees/graphs a lot easier? It does indeed. But raw pointers in C or C++ also make it easier than Rust. Sure, it’s very easy to screw things up leaking and/or corrupting memory. But it still quite possible to implement correctly, I did that more than once. Technically, you can usually do the same in Rust with unsafe pointers. Like the developers did to implement that LinkedHashMap for the Rust’s standard library. However, C++ is just better for writing unsafe code like this. After all, it evolved for decades being an unsafe language. Over that time, huge amount of stuff were implemented in the language (STL, esp. the checked version), runtime (debug heap), standalone tools (vtune, valgrind), and even OS (windbg) to help people implement e.g. graphs without leaking memory or exposing dangling pointers.