3 ms·

I didn't claim (and neither did kibwen, who unlike me is a major Rust contributor) that Rust's approaches around memory management didn't change. But your claim

by samth 11y ago

I didn't claim (and neither did kibwen, who unlike me is a major Rust contributor) that Rust's approaches around memory management didn't change. But your claim that "Lifetimes aren't regions" is false -- lifetimes are squarely in the 30-year research history of region systems.

coolsunglasses 11y ago
A region calculus[1], such as Tofte described, is not what I see in Rust as it exists today. It could've been so with typestate, if I understood the intent behind typestate correctly. If what Rust has is understood to be regions, then I need a couple of words for distinguishing the two. Ordinarily, I refer to what Rust/C++ have as "ownership types" and what exists in research as regions/RBMM/RC. [1]: http://www.researchgate.net/profile/Simon_Helsen/publication/220606930_Bisimilarity_for_the_Region_Calculus/links/00b495204f8809ae0c000000.pdf http://www.researchgate.net/profile/Simon_Helsen/publication... (the defintion provided here is what I understand "regions" to mean, as contrasted with what exists in C++ and Rust)
- comex 11y ago
  As someone not terribly familiar with the literature but familiar with Rust's type system, I just spend a few minutes googling various pages about region based memory management (including Tofte + Talpin) as well as skimming your link (not very hard, I admit), and I don't really understand what it lets you do (that doesn't exist in a roughly analogous form in Rust). Well, there's the fact that most of the papers describe region inference, while Rust is fully explicit, but that doesn't seem critical to the scheme to me. Out of curiosity, I'd be interested to see you elaborate on the difference. Also, I do not know what other 'PLs with similar facilities' exist with anywhere near as much effort put into them (other than Cyclone, which is dead). You mentioned C++, but it doesn't have lifetime checking at all, which is of course a core feature of Rust...
  - coolsunglasses 11y ago
    C++ doesn't cover the full extent of safety Rust offers at all, but there is a fair bit of overlap in how the functionality is packaged up WRT ownership types. I checked the docs and it looks like at least http://doc.rust-lang.org/0.12.0/guide-lifetimes.html#named-lifetimes http://doc.rust-lang.org/0.12.0/guide-lifetimes.html#named-l... is covered which was one of my objections. I still don't like that I can't design my own linearly typed constraints, but it appears that was never a goal to begin with. Not surprising given the lack of emphasis on expressive types. As it stands my only options for linear'ish types are indexed Monads in Haskell or building a model of linear types in a proof assistant or DTPL.
    - Manishearth 11y ago
      I and some others are working on a rough approximation to linear types here: https://github.com/Manishearth/humpty_dumpty https://github.com/Manishearth/humpty_dumpty A perfect implementation can be added to the language, but getting it to work perfectly with backcompat is hard so it might be made in 2.0.

by samth 11y ago

coolsunglasses 11y ago

A region calculus[1], such as Tofte described, is not what I see in Rust as it exists today. It could've been so with typestate, if I understood the intent behind typestate correctly. If what Rust has is understood to be regions, then I need a couple of words for distinguishing the two. Ordinarily, I refer to what Rust/C++ have as "ownership types" and what exists in research as regions/RBMM/RC. [1]: http://www.researchgate.net/profile/Simon_Helsen/publication/220606930_Bisimilarity_for_the_Region_Calculus/links/00b495204f8809ae0c000000.pdf http://www.researchgate.net/profile/Simon_Helsen/publication... (the defintion provided here is what I understand "regions" to mean, as contrasted with what exists in C++ and Rust)

comex 11y ago
As someone not terribly familiar with the literature but familiar with Rust's type system, I just spend a few minutes googling various pages about region based memory management (including Tofte + Talpin) as well as skimming your link (not very hard, I admit), and I don't really understand what it lets you do (that doesn't exist in a roughly analogous form in Rust). Well, there's the fact that most of the papers describe region inference, while Rust is fully explicit, but that doesn't seem critical to the scheme to me. Out of curiosity, I'd be interested to see you elaborate on the difference. Also, I do not know what other 'PLs with similar facilities' exist with anywhere near as much effort put into them (other than Cyclone, which is dead). You mentioned C++, but it doesn't have lifetime checking at all, which is of course a core feature of Rust...
- coolsunglasses 11y ago
  C++ doesn't cover the full extent of safety Rust offers at all, but there is a fair bit of overlap in how the functionality is packaged up WRT ownership types. I checked the docs and it looks like at least http://doc.rust-lang.org/0.12.0/guide-lifetimes.html#named-lifetimes http://doc.rust-lang.org/0.12.0/guide-lifetimes.html#named-l... is covered which was one of my objections. I still don't like that I can't design my own linearly typed constraints, but it appears that was never a goal to begin with. Not surprising given the lack of emphasis on expressive types. As it stands my only options for linear'ish types are indexed Monads in Haskell or building a model of linear types in a proof assistant or DTPL.
  - Manishearth 11y ago
    I and some others are working on a rough approximation to linear types here: https://github.com/Manishearth/humpty_dumpty https://github.com/Manishearth/humpty_dumpty A perfect implementation can be added to the language, but getting it to work perfectly with backcompat is hard so it might be made in 2.0.