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
editC++
editC++ features type aliasing using the using keyword.
using Distance = int;
C#
editC# since version 12 features type aliasing using the using keyword.[1]
using Distance = int;
Crystal
editCrystal features type aliasing using the alias keyword.[2]
alias Distance = Int32;
D
editD features type aliasing using the alias keyword.[3]
alias Distance = int;
Dart
editDart features type aliasing using the typedef keyword.[4]
typedef Distance = int;
Elixir
editElixir features type aliasing using @type.[5]
@type Distance :: integer
Elm
editElm features type aliasing using type alias.
type alias Distance = Int
F#
editF3 features type aliasing using the type keyword.
type Distance = int
Go
editGo features type aliasing using the type keyword and =.
type Distance = int
Hack
editHack features type aliasing using the newtype keyword.[6]
newtype Distance = int;
Haskell
editHaskell features type aliasing using the type keyword.[7]
type Distance = Int;
Julia
editJulia features type aliasing.[8]
const Distance = Int
Kotlin
editKotlin features type aliasing using the typealias keyword.[9]
typealias Distance = Int
Nim
editNim features type aliasing.[10]
type
Distance* = int
OCaml
editOCaml features type aliasing.[11]
type distance = int
Python
editPython 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
editRust features type aliasing using the type keyword.[13]
type Point = (u8, u8);
Scala
editScala can create type aliases using opaque types.[14]
object Logarithms:
opaque type Logarithm = Double
Swift
editSwift features type aliasing using the typealias keyword.
typealias Distance = Int;
TypeScript
editTypeScript features type aliasing using the type keyword.[15]
type Distance = number;
Zig
editZig 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.