7 ms·

This wasn't one of the question of the survey, but while having the right crowd around, I have to ask. When will Rust get 1. function head patterns like other

by cm3 10y ago

This wasn't one of the question of the survey, but while having the right crowd around, I have to ask. When will Rust get 1. function head patterns like other languages in the ML family, although Rust isn't really part of the family, but rather a distant cousin from another continent, which once played with ML and family during a summer vacation 2. support for naturally writing recursive functions

steveklabnik 10y ago
Can you elaborate on what #2 means to you?
- cm3 10y ago
  We are discouraged from writing recursive functions, which comes naturally when expressing many algorithms. Missing TCO is one cited reason to avoid it, so I gather we're not supposed to, generally speaking.
  - saghm 10y ago
    I don't think it's discouraged (a least, not in the sense of it being considered bad); I think they're just being explicit about what guarantees you have (or rather, don't have) for recursive functions
  - kibwen 10y ago
    Support for guaranteeing TCE is possible and has been proposed, but there remain a few open questions, e.g. what to do about local variables with destructors (personally I'd statically forbid them from being in scope at the end of tail-call recursive functions).
    - cm3 10y ago
      I know, that's why I wrote "when", knowing it's been considered, but it doesn't appear to be missed by enough developers. I'm just spoiled having used those two features, and anytime someone cites the ML family as part of Rust's influence, it reminds me of these two basic, missing features. Regarding semantics, without having thought about the Rust semantics too much, I'd suggest to check out the most prominent uses for recursive functions in OCaml, SML or Haskell, then try to consider that as the sweet spot to support in Rust.
Manishearth 10y ago
> Rust isn't really part of the family, but rather a distant cousin from another continent, which once played with ML and family during a summer vacation It's actually more of a sibling in the family who ran away from home at the age of 6 and fell in with the crowd on the wrong side of the tracks. Initially Rust was very much like ocaml. It isn't anymore :) Many of the normally-in-functional-languages features in Rust come from these days. Others were lost and re-added later. It's a very complex history. > function head patterns like other languages in the ML family could you elaborate? I'm not familiar with this feature (only have dabbled in sml). > support for naturally writing recursive functions yeah, I wish we had TCO.
- cm3 10y ago
  > It's actually more of a sibling in the family who ran away from home at the age of 6 and fell in with the crowd on the wrong side of the tracks. > Initially Rust was very much like ocaml. It isn't anymore :) Many of the normally-in-functional-languages features in Rust come from these days. Others were lost and re-added later. It's a very complex history. Yeah, having tried Rust in those days, I kinda stopped when it broke every week, and was then surprised with the surface of 1.0. It seemed like a different person to talk to. I've made my peace with the C'ification of Rust as the price to pay for attracting a large crowd of developers who grew up with C, C++, C#, Java, JavaScript, Ruby, Python, the list goes on. It's a reasonable sacrifice to make, but the two mentioned basic features aren't complex things to wish for. > could you elaborate? I'm not familiar with this feature (only have dabbled in sml). Imagine being able to hoist your match clauses into function head (signature?). oldEnoughToDrink :: Int -> Boolean oldEnoughToDrink 21 -> True oldEnoughToDrink _ -> False Not all languages with support for that force you to repeat the function name, and there are good arguments for/against. For example in Erlang, when you define an anonymous function, you do not repeat it: OldEnough = fun(21) -> true; (_) -> false end, Now, this may seem like a stupid little feature, but trust me when I say it's a natural feature to use like recursive functions after you're used to it.
  - Manishearth 10y ago
    Oh, yeah, I see what you mean by function head patterns. I'm aware of the coding pattern from Haskell, just didn't know the name :) I don't think Rust will get support for that. You can simulate it with macros (and, later, syntax extensions). Of course, that isn't as clean as pure language support. I know why it makes recursion (esp tail recursion) easier to use though. You could always bring it up on the forums and try though.
cm3 10y ago
I should add 3, Erlang's bit syntax, which would be a perfect and natural fit for the target of Rust code. It's a very natural DSL to parse or build (complex) bit streams. You don't necessarily have to add bit syntax comprehensions.

by cm3 10y ago

steveklabnik 10y ago

Can you elaborate on what #2 means to you?

cm3 10y ago
We are discouraged from writing recursive functions, which comes naturally when expressing many algorithms. Missing TCO is one cited reason to avoid it, so I gather we're not supposed to, generally speaking.
- saghm 10y ago
  I don't think it's discouraged (a least, not in the sense of it being considered bad); I think they're just being explicit about what guarantees you have (or rather, don't have) for recursive functions
- kibwen 10y ago
  Support for guaranteeing TCE is possible and has been proposed, but there remain a few open questions, e.g. what to do about local variables with destructors (personally I'd statically forbid them from being in scope at the end of tail-call recursive functions).
  - cm3 10y ago
    I know, that's why I wrote "when", knowing it's been considered, but it doesn't appear to be missed by enough developers. I'm just spoiled having used those two features, and anytime someone cites the ML family as part of Rust's influence, it reminds me of these two basic, missing features. Regarding semantics, without having thought about the Rust semantics too much, I'd suggest to check out the most prominent uses for recursive functions in OCaml, SML or Haskell, then try to consider that as the sweet spot to support in Rust.

Manishearth 10y ago

> Rust isn't really part of the family, but rather a distant cousin from another continent, which once played with ML and family during a summer vacation It's actually more of a sibling in the family who ran away from home at the age of 6 and fell in with the crowd on the wrong side of the tracks. Initially Rust was very much like ocaml. It isn't anymore :) Many of the normally-in-functional-languages features in Rust come from these days. Others were lost and re-added later. It's a very complex history. > function head patterns like other languages in the ML family could you elaborate? I'm not familiar with this feature (only have dabbled in sml). > support for naturally writing recursive functions yeah, I wish we had TCO.

cm3 10y ago
> It's actually more of a sibling in the family who ran away from home at the age of 6 and fell in with the crowd on the wrong side of the tracks. > Initially Rust was very much like ocaml. It isn't anymore :) Many of the normally-in-functional-languages features in Rust come from these days. Others were lost and re-added later. It's a very complex history. Yeah, having tried Rust in those days, I kinda stopped when it broke every week, and was then surprised with the surface of 1.0. It seemed like a different person to talk to. I've made my peace with the C'ification of Rust as the price to pay for attracting a large crowd of developers who grew up with C, C++, C#, Java, JavaScript, Ruby, Python, the list goes on. It's a reasonable sacrifice to make, but the two mentioned basic features aren't complex things to wish for. > could you elaborate? I'm not familiar with this feature (only have dabbled in sml). Imagine being able to hoist your match clauses into function head (signature?). oldEnoughToDrink :: Int -> Boolean oldEnoughToDrink 21 -> True oldEnoughToDrink _ -> False Not all languages with support for that force you to repeat the function name, and there are good arguments for/against. For example in Erlang, when you define an anonymous function, you do not repeat it: OldEnough = fun(21) -> true; (_) -> false end, Now, this may seem like a stupid little feature, but trust me when I say it's a natural feature to use like recursive functions after you're used to it.
- Manishearth 10y ago
  Oh, yeah, I see what you mean by function head patterns. I'm aware of the coding pattern from Haskell, just didn't know the name :) I don't think Rust will get support for that. You can simulate it with macros (and, later, syntax extensions). Of course, that isn't as clean as pure language support. I know why it makes recursion (esp tail recursion) easier to use though. You could always bring it up on the forums and try though.

cm3 10y ago

I should add 3, Erlang's bit syntax, which would be a perfect and natural fit for the target of Rust code. It's a very natural DSL to parse or build (complex) bit streams. You don't necessarily have to add bit syntax comprehensions.