Comparison of programming languages (algebraic data type)
This article compares the syntax for defining and instantiating an algebraic data type (ADT), sometimes also referred to as a tagged union, in various programming languages.
Examples of algebraic data types[edit]
Ceylon[edit]
In Ceylon, an ADT may be defined with:[1]
abstract class Tree() of empty | Node {} object empty extends Tree() {} final class Node(shared Integer val, shared Tree left, shared Tree right) extends Tree() {}
And instantiated as:
value myTree = Node(42, Node(0, empty, empty), empty);
Clean[edit]
In Clean, an ADT may be defined with:[2]
:: Tree = Empty | Node Int Tree Tree
And instantiated as:
myTree = Node 42 (Node 0 Empty Empty) Empty
Coq[edit]
In Coq, an ADT may be defined with:[3]
Inductive tree : Type := | empty : tree | node : nat -> tree -> tree -> tree.
And instantiated as:
Definition my_tree := node 42 (node 0 empty empty) empty.
C++[edit]
In C++, an ADT may be defined with:[4]
struct Empty final {}; struct Node final { int value; std::unique_ptr<std::variant<Empty, Node>> left; std::unique_ptr<std::variant<Empty, Node>> right; }; using Tree = std::variant<Empty, Node>;
And instantiated as:
Tree myTree { Node{ 42, std::make_unique<Tree>(Node{ 0, std::make_unique<Tree>(), std::make_unique<Tree>() }), std::make_unique<Tree>() } };
Dart[edit]
In Dart, an ADT may be defined with:[5]
sealed class Tree {} final class Empty extends Tree {} final class Node extends Tree { final int value; final Tree left, right; Node(this.value, this.left, this.right); }
And instantiated as:
final myTree = Node(42, Node(0, Empty(), Empty()), Empty());
Elm[edit]
In Elm, an ADT may be defined with:[6]
type Tree = Empty | Node Int Tree Tree
And instantiated as:
myTree = Node 42 (Node 0 Empty Empty) Empty
F#[edit]
In F#, an ADT may be defined with:[7]
type Tree = | Empty | Node of int * Tree * Tree
And instantiated as:
let myTree = Node(42, Node(0, Empty, Empty), Empty)
F*[edit]
In F*, an ADT may be defined with:[8]
type tree = | Empty : tree | Node : value:nat -> left:tree -> right:tree -> tree
And instantiated as:
let my_tree = Node 42 (Node 0 Empty Empty) Empty
Free Pascal[edit]
In Free Pascal (in standard ISO Pascal mode[9]), an ADT may be defined with variant records:[10]
{$mode ISO} program MakeTree; type TreeKind = (Empty, Node); PTree = ^Tree; Tree = record case Kind: TreeKind of Empty: (); Node: ( Value: Integer; Left, Right: PTree; ); end;
And instantiated as:
var MyTree: PTree; begin new(MyTree, Node); with MyTree^ do begin Value := 42; new(Left, Node); with Left^ do begin Value := 0; new(Left, Empty); new(Right, Empty); end; new(Right, Empty); end; end.
Haskell[edit]
In Haskell, an ADT may be defined with:[11]
data Tree = Empty | Node Int Tree Tree
And instantiated as:
myTree = Node 42 (Node 0 Empty Empty) Empty
Haxe[edit]
In Haxe, an ADT may be defined with:[12]
enum Tree { Empty; Node(value:Int, left:Tree, right:Tree); }
And instantiated as:
var myTree = Node(42, Node(0, Empty, Empty), Empty);
Hope[edit]
In Hope, an ADT may be defined with:[13]
data tree == empty ++ node (num # tree # tree);
And instantiated as:
dec mytree : tree; --- mytree <= node (42, node (0, empty, empty), empty);
Idris[edit]
In Idris, an ADT may be defined with:[14]
data Tree = Empty | Node Nat Tree Tree
And instantiated as:
myTree : Tree myTree = Node 42 (Node 0 Empty Empty) Empty
Java[edit]
In Java, an ADT may be defined with:[15]
sealed interface Tree { record Empty() implements Tree {} record Node(int value, Tree left, Tree right) implements Tree {} }
And instantiated as:
var myTree = new Tree.Node( 42, new Tree.Node(0, new Tree.Empty(), new Tree.Empty()), new Tree.Empty() );
Julia[edit]
In Julia, an ADT may be defined with:[16]
struct Empty end struct Node value::Int left::Union{Empty, Node} right::Union{Empty, Node} end const Tree = Union{Empty, Node}
And instantiated as:
mytree = Node(42, Node(0, Empty(), Empty()), Empty())
Kotlin[edit]
In Kotlin, an ADT may be defined with:[17]
sealed class Tree { object Empty : Tree() data class Node(val value: Int, val left: Tree, val right: Tree) : Tree() }
And instantiated as:
val myTree = Tree.Node( 42, Tree.Node(0, Tree.Empty, Tree.Empty), Tree.Empty, )
Limbo[edit]
In Limbo, an ADT may be defined with:[18]
Tree: adt { pick { Empty => Node => value: int; left: ref Tree; right: ref Tree; } };
And instantiated as:
myTree := ref Tree.Node( 42, ref Tree.Node(0, ref Tree.Empty(), ref Tree.Empty()), ref Tree.Empty() );
Mercury[edit]
In Mercury, an ADT may be defined with:[19]
:- type tree ---> empty ; node(int, tree, tree).
And instantiated as:
:- func my_tree = tree. my_tree = node(42, node(0, empty, empty), empty).
Miranda[edit]
In Miranda, an ADT may be defined with:[20]
tree ::= Empty | Node num tree tree
And instantiated as:
my_tree = Node 42 (Node 0 Empty Empty) Empty
Nemerle[edit]
In Nemerle, an ADT may be defined with:[21]
variant Tree { | Empty | Node { value: int; left: Tree; right: Tree; } }
And instantiated as:
def myTree = Tree.Node( 42, Tree.Node(0, Tree.Empty(), Tree.Empty()), Tree.Empty(), );
Nim[edit]
In Nim, an ADT may be defined with:[22]
type TreeKind = enum tkEmpty tkNode Tree = ref TreeObj TreeObj = object case kind: TreeKind of tkEmpty: discard of tkNode: value: int left, right: Tree
And instantiated as:
let myTree = Tree(kind: tkNode, value: 42, left: Tree(kind: tkNode, value: 0, left: Tree(kind: tkEmpty), right: Tree(kind: tkEmpty)), right: Tree(kind: tkEmpty))
OCaml[edit]
In OCaml, an ADT may be defined with:[23]
type tree = | Empty | Node of int * tree * tree
And instantiated as:
let my_tree = Node (42, Node (0, Empty, Empty), Empty)
Opa[edit]
In Opa, an ADT may be defined with:[24]
type tree = { empty } or { node, int value, tree left, tree right }
And instantiated as:
my_tree = { node, value: 42, left: { node, value: 0, left: { empty }, right: { empty } }, right: { empty } }
OpenCog[edit]
This section needs expansion. You can help by adding to it. (December 2021) |
In OpenCog, an ADT may be defined with:[25]
PureScript[edit]
In PureScript, an ADT may be defined with:[26]
data Tree = Empty | Node Int Tree Tree
And instantiated as:
myTree = Node 42 (Node 0 Empty Empty) Empty
Python[edit]
In Python, an ADT may be defined with:[27]
from __future__ import annotations from dataclasses import dataclass @dataclass class Empty: pass @dataclass class Node: value: int left: Tree right: Tree Tree = Empty | Node
And instantiated as:
my_tree = Node(42, Node(0, Empty(), Empty()), Empty())
Racket[edit]
In Typed Racket, an ADT may be defined with:[28]
(struct Empty ()) (struct Node ([value : Integer] [left : Tree] [right : Tree])) (define-type Tree (U Empty Node))
And instantiated as:
(define my-tree (Node 42 (Node 0 (Empty) (Empty)) (Empty)))
Reason[edit]
Reason[edit]
In Reason, an ADT may be defined with:[29]
type Tree = | Empty | Node(int, Tree, Tree);
And instantiated as:
let myTree = Node(42, Node(0, Empty, Empty), Empty);
ReScript[edit]
In ReScript, an ADT may be defined with:[30]
type rec Tree = | Empty | Node(int, Tree, Tree)
And instantiated as:
let myTree = Node(42, Node(0, Empty, Empty), Empty)
Rust[edit]
In Rust, an ADT may be defined with:[31]
enum Tree { Empty, Node(i32, Box<Tree>, Box<Tree>), }
And instantiated as:
let my_tree = Tree::Node( 42, Box::new(Tree::Node(0, Box::new(Tree::Empty), Box::new(Tree::Empty)), Box::new(Tree::Empty), );
Scala[edit]
Scala 2[edit]
In Scala 2, an ADT may be defined with:[citation needed]
sealed abstract class Tree extends Product with Serializable object Tree { final case object Empty extends Tree final case class Node(value: Int, left: Tree, right: Tree) extends Tree }
And instantiated as:
val myTree = Tree.Node( 42, Tree.Node(0, Tree.Empty, Tree.Empty), Tree.Empty )
Scala 3[edit]
In Scala 3, an ADT may be defined with:[32]
enum Tree: case Empty case Node(value: Int, left: Tree, right: Tree)
And instantiated as:
val myTree = Tree.Node( 42, Tree.Node(0, Tree.Empty, Tree.Empty), Tree.Empty )
Standard ML[edit]
In Standard ML, an ADT may be defined with:[33]
datatype tree = EMPTY | NODE of int * tree * tree
And instantiated as:
val myTree = NODE (42, NODE (0, EMPTY, EMPTY), EMPTY)
Swift[edit]
In Swift, an ADT may be defined with:[34]
enum Tree { case empty indirect case node(Int, Tree, Tree) }
And instantiated as:
let myTree: Tree = .node(42, .node(0, .empty, .empty), .empty)
TypeScript[edit]
In TypeScript, an ADT may be defined with:[35]
type Tree = | { kind: "empty" } | { kind: "node"; value: number; left: Tree; right: Tree };
And instantiated as:
const myTree: Tree = { kind: "node", value: 42, left: { kind: "node", value: 0, left: { kind: "empty" }, right: { kind: "empty" }, }, right: { kind: "empty" }, };
Visual Prolog[edit]
In Visual Prolog, an ADT may be defined with:[36]
domains tree = empty; node(integer, tree, tree).
And instantiated as:
constants my_tree : tree = node(42, node(0, empty, empty), empty).
References[edit]
- ^ "Eclipse Ceylon: Union, intersection, and enumerated types". ceylon-lang.org. Archived from the original on 2022-12-26. Retrieved 2021-11-29.
- ^ "Clean 2.2 Ref Man". clean.cs.ru.nl. Retrieved 2021-11-29.
- ^ "Inductive types and recursive functions — Coq 8.14.1 documentation". coq.inria.fr. Retrieved 2021-11-30.
- ^ "std::variant - cppreference.com". en.cppreference.com. Retrieved 2021-12-04.
- ^ "Patterns". dart.dev. Retrieved 2023-09-28.
- ^ "Custom Types · An Introduction to Elm". guide.elm-lang.org. Retrieved 2021-11-29.
- ^ cartermp. "Discriminated Unions - F#". docs.microsoft.com. Retrieved 2021-11-29.
- ^ "Inductive types and pattern matching — Proof-Oriented Programming in F* documentation". www.fstar-lang.org. Retrieved 2021-12-06.
- ^ "Mode iso". wiki.freepascal.org. Retrieved 2024-05-26.
- ^ "Record types". www.freepascal.org. Retrieved 2021-12-05.
- ^ "4 Declarations and Bindings". www.haskell.org. Retrieved 2021-12-07.
- ^ "Enum Instance". Haxe - The Cross-platform Toolkit. Retrieved 2021-11-29.
- ^ "Defining your own data types". 2011-08-10. Archived from the original on 2011-08-10. Retrieved 2021-12-03.
- ^ "Types and Functions — Idris2 0.0 documentation". idris2.readthedocs.io. Retrieved 2021-11-30.
- ^ "JEP 409: Sealed Classes". openjdk.java.net. Retrieved 2021-12-05.
- ^ "Types · The Julia Language". docs.julialang.org. Retrieved 2021-12-03.
- ^ "Sealed classes | Kotlin". Kotlin Help. Retrieved 2021-11-29.
- ^ Stanley-Marbell, Phillip (2003). Inferno Programming with Limbo. Wiley. pp. 67–71. ISBN 978-0470843529.
- ^ "The Mercury Language Reference Manual: Discriminated unions". www.mercurylang.org. Retrieved 2021-12-07.
- ^ "An Overview of Miranda". www.cs.kent.ac.uk. Retrieved 2021-12-04.
- ^ "Basic Variants · rsdn/nemerle Wiki". GitHub. Retrieved 2021-12-03.
- ^ "Nim Manual". nim-lang.org. Retrieved 2021-11-29.
- ^ "OCaml - The OCaml language". ocaml.org. Retrieved 2021-12-07.
- ^ "The type system · MLstate/opalang Wiki". GitHub. Retrieved 2021-12-07.
- ^ "Type constructor - OpenCog". wiki.opencog.org. Retrieved 2021-12-07.
- ^ purescript/documentation, PureScript, 2021-11-24, retrieved 2021-11-30
- ^ PEP 484 – Type Hints, Python
- ^ "2 Beginning Typed Racket". docs.racket-lang.org. Retrieved 2021-12-04.
- ^ "Variants · Reason". reasonml.github.io. Retrieved 2021-11-30.
- ^ "Variant | ReScript Language Manual". ReScript Documentation. Retrieved 2021-11-30.
- ^ "enum - Rust". doc.rust-lang.org. Retrieved 2021-11-29.
- ^ "Algebraic Data Types". Scala Documentation. Retrieved 2021-11-29.
- ^ "Defining datatypes". homepages.inf.ed.ac.uk. Retrieved 2021-12-01.
- ^ "Enumerations — The Swift Programming Language (Swift 5.5)". docs.swift.org. Retrieved 2021-11-29.
- ^ "Documentation - TypeScript for Functional Programmers". www.typescriptlang.org. Retrieved 2021-11-29.
- ^ "Language Reference/Domains - wiki.visual-prolog.com". wiki.visual-prolog.com. Retrieved 2021-12-07.