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by simonask 45 days ago
It bothers me too, maybe for different reasons, as an experienced rustacean. Code like this is a world of pain (in any language, might I add, even though Rust is the only one that shows you why with the syntax).

Internally shared ownership is a huge anti-pattern and rarely achieves what you’re actually trying to do. Graphs like these are much better represented by splitting the topology from the node data, and using indices or keys to form edges instead of (smart) pointers.

You can use pointers, but then the correct choice is actually raw pointers and `unsafe`, with a safe whole-graph-level API for traversal and access. This is what Rust’s own collection types do internally.
1 comments
BiteCode_dev 45 days ago
Do you have a simple example of how this is done correctly?

I always heard that but comming from Python internal references would be the way to go so it's not natural to me.

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simonask 45 days ago
Depending on the shape of the graph (arbitrarily connected, DAG, etc.), it just boils down to whatever convenient way you have of storing lists.

Node data in one list. Indices of node parents in another list of the same length. If you need to find children quickly, you can have another list of lists containing children indices.

The key is to consider the node’s position in the list as its ID, and refer to nodes by that index instead of the pointer.

In most cases, this model is both easier to work with and more performant. For example, you can usually get by with 32-bit indices instead of 64-bit pointers, so things are much more likely to be in cache.

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BiteCode_dev 45 days ago
Thanks. So you basically make pointers manually with your own separated stack. Wouldn't make sense to have the ability to just allocate anew stact you dedicate to a graph and let the ownership system deals with it for you? Seems like a missing abstraction.
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michalsustr 43 days ago
I recently saw a submission here that does that, by essentially implementing GC in Rust. It is not beginner material though. https://kyju.org/blog/tokioconf-2026/

Edit: also the simplest way how to do cyclic structures is to heap-allocate via Box and leak memory. Box::leak This is also mentioned in the linked article.

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andriy_koval 45 days ago
All these Weak, RC are needed for allocation/deallocation of memory. Having data in list with indexes means you don't have this functionality.
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