Type aliasing
Type aliasing is a feature in some programming languages that allows creating a reference to a type using another name. It does not create a new type hence does not increase type safety. It can be used to shorten a long name. Languages allowing type aliasing include: C++, C# Crystal, D, Dart, Elixir, Elm, F#, Go, Hack, Haskell, Julia, Kotlin, Nim, OCaml, Python, Rust, Scala, Swift and TypeScript.
Example
[edit]C++
[edit]C++ features type aliasing using the using keyword.
using Distance = int;
C#
[edit]C# since version 12 features type aliasing using the using keyword.[1]
using Distance = int;
Crystal
[edit]Crystal features type aliasing using the alias keyword.[2]
alias Distance = Int32;
D
[edit]D features type aliasing using the alias keyword.[3]
alias Distance = int;
Dart
[edit]Dart features type aliasing using the typedef keyword.[4]
typedef Distance = int;
Elixir
[edit]Elixir features type aliasing using @type.[5]
@type Distance :: integer
Elm
[edit]Elm features type aliasing using type alias.
type alias Distance = Int
F#
[edit]F3 features type aliasing using the type keyword.
type Distance = int
Go
[edit]Go features type aliasing using the type keyword and =.
type Distance = int
Hack
[edit]Hack features type aliasing using the newtype keyword.[6]
newtype Distance = int;
Haskell
[edit]Haskell features type aliasing using the type keyword.[7]
type Distance = Int;
Julia
[edit]Julia features type aliasing.[8]
const Distance = Int
Kotlin
[edit]Kotlin features type aliasing using the typealias keyword.[9]
typealias Distance = Int
Nim
[edit]Nim features type aliasing.[10]
type
Distance* = int
OCaml
[edit]OCaml features type aliasing.[11]
type distance = int
Python
[edit]Python features type aliasing.[12]
Vector = list[float]
Type aliases may be marked with TypeAlias to make it explicit that the statement is a type alias declaration, not a normal variable assignment.
from typing import TypeAlias
Vector: TypeAlias = list[float]
Rust
[edit]Rust features type aliasing using the type keyword.[13]
type Point = (u8, u8);
Scala
[edit]Scala can create type aliases using opaque types.[14]
object Logarithms:
opaque type Logarithm = Double
Swift
[edit]Swift features type aliasing using the typealias keyword.
typealias Distance = Int;
TypeScript
[edit]TypeScript features type aliasing using the type keyword.[15]
type Distance = number;
Zig
[edit]Zig features type aliasing by assigning a data type to a constant.[16]
const distance = u32;
References
[edit]- ^ "Alias any type - C# 12.0 draft feature specifications". learn.microsoft.com. 16 August 2023. Retrieved 23 February 2024.
- ^ "alias - Crystal". crystal-lang.org. Retrieved 21 February 2024.
- ^ "Alias Alias - D Programming Language". dlang.org. Retrieved 18 June 2023.
- ^ "Typedefs". dart.dev. Retrieved 18 June 2023.
- ^ "Typespecs and behaviours". elixir-lang.github.com. Retrieved 23 June 2023.
- ^ "Types: Type Aliases". docs.hhvm.com. Retrieved 18 June 2023.
- ^ "Type synonym - HaskellWiki". wiki.haskell.org. Retrieved 18 June 2023.
- ^ "Types · The Julia Language". docs.julialang.org. Retrieved 23 June 2023.
- ^ "Type aliases | Kotlin". Kotlin Help. Retrieved 18 June 2023.
- ^ "Nim by Example - Types". nim-by-example.github.io. Retrieved 21 June 2023.
- ^ "OCaml reference manual". ocaml.org. Retrieved 23 April 2024.
- ^ "typing — Support for type hints". Python documentation. Python Software Foundation. Retrieved 18 June 2023.
- ^ "Type aliases - The Rust Reference". doc.rust-lang.org. Retrieved 18 June 2023.
- ^ "Opaque Types". Scala Documentation. Retrieved 18 June 2023.
- ^ "Documentation - Everyday Types". www.typescriptlang.org. Retrieved 18 June 2023.
- ^ "Documentation - The Zig Programming Language". ziglang.org. Retrieved 14 October 2024.