3 ms·

Rust definitely has higher order functions, but it doesn't have higher kinded types required for certain things (like monads). You may have got these confused.

wyager 10y ago
Rust has very limited higher-order functions. True functional-style HOFs require passing around arbitrarily-sized heap closures, which doesn't work with rust's memory model. You cannot, for example, have a vector of functions in rust. You can sort of get it with boxed closures, but it's very inconvenient compared to in any of the languages I mentioned. That's why I didn't include it.
- vertex-four 10y ago
  Boxing things is the way to get arbitrarily-sized things in Rust. I've worked with vectors of closures - it works quite nicely.
  - wyager 10y ago
    It may work quite nicely by whatever standard you're used to, but it's extremely inconvenient compared to languages that actually make a habit of using HOFs. There's a reason people don't usually use HOFs in Rust outside of a few easily inlinable use cases. The standard library doesn't even have any sort of composition or application operators, because it would be too unwieldy to use.
    - vertex-four 10y ago
      No, the standard library doesn't contain many of the things that Haskell's does because it's not Haskell, and people haven't really been asking for them like they have a variety of other things. And the reason people don't use them widely is that there's often better designs than passing around closures - lifetimes make useful mutation of closures' environments difficult, Rust largely revolves around mutation, so it's more common to invert the control flow (have functions return a command and interpret it, possibly in a loop, rather than have them take a closure) except in certain self-contained situations. That doesn't change the existence of HOFs.
      - wyager 10y ago
        Sounds to me like you're saying the exact same thing I am, which is that HOFs are too inconvenient to be practical in Rust.

wyager 10y ago

Rust has very limited higher-order functions. True functional-style HOFs require passing around arbitrarily-sized heap closures, which doesn't work with rust's memory model. You cannot, for example, have a vector of functions in rust. You can sort of get it with boxed closures, but it's very inconvenient compared to in any of the languages I mentioned. That's why I didn't include it.

vertex-four 10y ago
Boxing things is the way to get arbitrarily-sized things in Rust. I've worked with vectors of closures - it works quite nicely.
- wyager 10y ago
  It may work quite nicely by whatever standard you're used to, but it's extremely inconvenient compared to languages that actually make a habit of using HOFs. There's a reason people don't usually use HOFs in Rust outside of a few easily inlinable use cases. The standard library doesn't even have any sort of composition or application operators, because it would be too unwieldy to use.
  - vertex-four 10y ago
    No, the standard library doesn't contain many of the things that Haskell's does because it's not Haskell, and people haven't really been asking for them like they have a variety of other things. And the reason people don't use them widely is that there's often better designs than passing around closures - lifetimes make useful mutation of closures' environments difficult, Rust largely revolves around mutation, so it's more common to invert the control flow (have functions return a command and interpret it, possibly in a loop, rather than have them take a closure) except in certain self-contained situations. That doesn't change the existence of HOFs.
    - wyager 10y ago
      Sounds to me like you're saying the exact same thing I am, which is that HOFs are too inconvenient to be practical in Rust.