Rust uses a reference-counting collector for allocations that go beyond what the borrow-checker can handle. You have to explicitly use the RC allocation. Reference counting, as you may know is a more predictable memory allocation technique and works well for many data structures, such as trees (binary or otherwise). It however has problems with cyclic data structures (doubly-linked lists, general graphs, etc.). Since the reference-counted allocations are explicit, it is usually not onerous for the programmer to handle the de-allocation of these data structures. Having a built-in RC collector is a big win over C/C++ - your effective alternatives.

If you aren’t willing to deal with the reference counter, your closest choices to Rust are D, Nim, or (less close) Go. But if you look at the benchmark game site, you’ll see that garbage-collected languages are often a factor of 3 slower than Rust/C/C++. If that degree of performance matters to you, I think you should use Rust rather than C or C++. If it doesn’t, you have a plethora of choices, including Go, Java, C#, Haskell, Python, Lisp, or (my favoured) Smalltalk.

../Dave

On Jan 1, 2020, 6:09 PM -0500, Nicholas Krause <xerofoify@gmail.com>, wrote:

On 1/1/20 11:44 AM, David Mason wrote:

Borrowing is entirely a compile-time analysis. There is no runtime impact (other than the fact that you can get away without a garbage collector - in a safe way).

The Learn Rust the Dangerous way article is very good, by the way! I heartily endorse it for the C-philes among GTALUG. If you haven’t read it, one of the things that might convince you is that the leaderboard for this highly-optimized n-body simulation has Rust in the first-place https://benchmarksgame-team.pages.debian.net/benchmarksgame/performance/nbody.html - faster than C, C++, Fortran or Ada. I’ve added it to my list of resources for Rust: https://cps506.scs.ryerson.ca/Resources/rust.html

Ownership makes sense its a compiler version of smart pointers. My concerns are still:
 What about circular references in which the owner depends on data from the child
but cannot free it due to the knowledge also depending on the parent. Binary trees
are a problem here. Or you must assume like garbage collectors this  never occurs
and this is one way to get memory leaks in a lot of garbage collectors fast.

Rust seems fine for a lot of things but this one case does not seem solved at least
in my knowledge or is  assumed to not be a big issue and I could be wrong but
from my limited research it appears not,
Nick

../Dave

On Dec 31, 2019, 4:22 PM -0500, Nicholas Krause via talk <talk@gtalug.org>, wrote:

On 12/31/19 11:57 AM, D. Hugh Redelmeier via talk wrote:

| From: Tom Low-Shang via talk <talk@gtalug.org>

| I'm interested in your thoughts on Rust if you attended the talk.

The talk was mostly a guided creation of a program. So I don't think
that it answered any of your questions.

| I'm currently learning Rust the old fashioned hacker way (from books and
| other people's code :)). My biggest mistake was trying to use Rust with
| SDL2 to display some graphics. My head still hurts from banging it into
| a wall called 'lifetimes'. :)

The whole idea of borrowing etc. is fundamental to Rust and how it
ensures safety. Without garbage collection. If you don't like or
understand this approach, Rust isn't useful.

Hugh,
I've a question about how borrowing is implemented internally as it can lead
to a problem, if I allow lots of memory can my program stall because of this
at the end of a block. In addition due to this does borrow checking
limit or
not implement something like freelists or caching to get better usage of the
CPU cache as that's also a concern.

Thanks,
Nick

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