Rust RAII is better than the Haskell bracket pattern

Re:Rust RAII is better than the Haskell bracket pattern by steveklabnik on Tuesday October 09, 2018 @10:00AM (#18176015)

That doesn't change much; the point is that (in many languages), variables going into or out of scopes don't fiddle with the ref count[1], and so people assume that something will live until they make the count go down explicitly.

It also only refers to ownership, not borrowing, and both are equally important.

Beyond that, what I'm saying is something more meta: It doesn't really matter if this analogy is spot-on or not; it's got enough wiggle room in it that I've seen it trip up beginners. Maybe that's because they misunderstand the analogy, but given that its point is to convey understanding, that means that it isn't a great analogy, in my experience. YMMV.

1: directly, of course; this also depends on the language.

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Re:Rust RAII is better than the Haskell bracket pattern by rbehrends on Tuesday October 09, 2018 @10:12AM (#18176109)

> It also only refers to ownership, not borrowing, and both are equally important.

I addressed borrowing above. Borrowing is proving lifetime subset properties and that you therefore can avoid increasing the virtual reference count.

And this is not about whether this is useful for beginners. It is to illustrate inherent limitations of the approach.

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Re:Rust RAII is better than the Haskell bracket pattern by steveklabnik on Tuesday October 09, 2018 @10:19AM (#18176170)

> I addressed borrowing above. Borrowing is proving lifetime subset properties and that

Right, so what I'm saying is, the description of borrowing doesn't really fit in with the reference counting aspect of the analogy, so it ends up being separate from it.

> And this is not about whether this is useful for beginners.

Right, that was my point. :)

I mean, in the end, do what you'd like. All I'm saying is that I've seen this analogy lead to tons of confusion. YMMV.

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