Most functional languages, like Haskell, ML family (SML, OCaml, F#). They're usually not using an enum keyword though.
this post was submitted on 01 Jun 2022
8 points (100.0% liked)
Rust Programming
8011 readers
1 users here now
founded 5 years ago
MODERATORS
Yeah, in language theory, this kind of thing is called an "Algebraic Data Type": https://en.wikipedia.org/wiki/Algebraic_data_type
Typed functional languages usually do, as mentioned by others. This is form of Algebraic Data Type called a Sum Type (as oppose to a Product type, which is basically a normal struct).
Here's some examples of creating a binary tree in different languages (also Lemmy's code formatter is terrible)
Examples
Haskell
data Tree a = Empty | Leaf a | Node (Tree a) (Tree a)
F#
type Tree<'a> = Empty | Leaf of 'a | Node of (Tree<'a> * Tree<'a>)
Scala
sealed trait Tree[+A]
case class Empty[A]() extends Tree[A]
case class Leaf[A](a: A) extends Tree[A]
case class Node[A](left: Tree[A], right: Tree[A]) extends Tree[A]
Rust
enum Tree<T> {
Empty,
Leaf(T),
Node(Box<Tree<T>>, Box<Tree<T>>),
}
Can you give examples? From the description, it seems like most languages (like Java) can store data in enums?
I think they mean that enum variants can contain fields, i.e. individual variants are themselves structs or tuple structs. AFAIK the closest thing to this in a C-like lang would be a tagged union type.
oh yes thats what i mean. Coded in rust, loved this feature, went back to python a bit and became sad that I couldnt do the same. Feels stupid that a variable can be different types depending on the situation, and having a dataclass where just one field is relevant seems too dumb