Content deleted Content added
Elm is also available on Linux and Arm Tags: Mobile edit Mobile web edit |
|||
| (16 intermediate revisions by 11 users not shown) | |||
Line 4:
| name = Elm
| logo = Elm logo.svg
| logo caption = The Elm tangram
| paradigm = [[Functional programming|functional]]
Line 13 ⟶ 12:
| latest release date = {{Start date and age|2019|10|21}}<ref>{{Cite web |url=https://github.com/elm/compiler/releases |title=Releases: elm/Compiler |website=[[GitHub]]}}</ref>
| typing = [[Static typing|static]], [[Strong and weak typing|strong]], [[Type inference|inferred]]
| platform = [[x86-64]], [[AArch64|ARM]]
| operating system = [[macOS]], [[Microsoft Windows|Windows]], [[Linux]]
| license = [[Permissive license|Permissive]] ([[BSD license|Revised BSD]])<ref name=license>{{cite web |url=https://github.com/elm/compiler/blob/master/LICENSE |title=elm/compiler |website=GitHub|date=16 October 2021}}</ref>
| file ext = .elm
| website = {{Official URL}}
| influenced by = [[Haskell]], [[Standard ML]], [[OCaml]], [[F Sharp (programming language)|F#]]
| influenced = [[Redux (JavaScript library)|Redux]],<ref>{{cite web |url=https://redux.js.org/introduction/prior-art |title=Prior Art - Redux |website=redux.js.org|date=28 April 2024 }}</ref> [[Rust (programming language)|Rust]],<ref>{{Cite web |title=
}}
Line 25 ⟶ 24:
== History ==
Elm was initially designed by Evan Czaplicki as his thesis in 2012.<ref>{{cite web |url=https://elm-lang.org/assets/papers/concurrent-frp.pdf |title=Elm: Concurrent FRP for Functional GUIs}}</ref> The first release of Elm came with many examples and an online editor that made it easy to try out in a [[web browser]].<ref>{{cite web |url=https://elm-lang.org/try |title=Try Elm |website=elm-lang.org |access-date=
The initial implementation of the Elm compiler targets HyperText Markup Language ([[HTML]]), [[Cascading Style Sheets]] (CSS), and [[JavaScript]].<ref>{{cite web |url=https://github.com/elm/compiler |title=elm/compiler |website=GitHub|date=16 October 2021}}</ref> The set of core tools has continued to expand, now including a [[read–eval–print loop]] (REPL),<ref>{{cite web |url=https://elm-lang.org/news/repl |title=repl |website=elm-lang.org}}</ref> [[Package management system|package manager]],<ref>{{cite web |url=https://elm-lang.org/news/package-manager |title=package manager |website=elm-lang.org}}</ref> time-travelling debugger,<ref>{{cite web |url=https://elm-lang.org/news/time-travel-made-easy |title=Home |website=elm-lang.org}}</ref> and installers for [[macOS]] and [[Microsoft Windows|Windows]].<ref>{{cite web |url=https://guide.elm-lang.org/install.html |title=Install |website=guide.elm-lang.org}}</ref> Elm also has an ecosystem of community created [[Library (computing)|libraries]],<ref>{{Cite web |url=https://package.elm-lang.org/ |title=Elm packages |website=Elm-lang.org}}</ref> and Ellie, an advanced online editor that allows saved work and including community libraries.<ref>{{Cite web |url=https://ellie-app.com/ |title=Ellie |website=Ellie-app.com}}</ref>
== Features ==
Elm has a small set of language constructs, including traditional if-expressions, let-expressions for storing local values, and case-expressions for [[pattern matching]].<ref name="syntax">{{cite web |url=
=== Immutability ===
Line 44 ⟶ 43:
Rather than allow any value to be implicitly nullable (such as JavaScript's <code>undefined</code> or a [[null pointer]]), Elm's standard library defines a <code>Maybe a</code> type. Code that produces or handles an optional value does so explicitly using this type, and all other code is guaranteed a value of the claimed type is actually present.
Elm provides a limited number of built-in [[type class|type classes]]
=== Module system ===
Line 56 ⟶ 55:
=== Backend ===
Elm does not officially support server-side development. Czaplicki does consider it a primary goal at this point, but public progress on this front has been slow. Nevertheless, there are several independent projects which attempt to explore Elm on the backend.
The primary production-ready full-stack Elm platform is Lamdera, an open-core "unfork" of Elm.<ref>{{Cite AV media |url=https://www.youtube.com/watch?v=nSrucNcwlA8 |title=Mario Rogic - Elm as a Service |date=2019-11-28 |last=Elm Europe |access-date=2025-03-27 |via=YouTube}}</ref><ref>{{Cite AV media |url=https://www.youtube.com/watch?v=3Nn5meBieh4 |title=Building a Meetup clone on Lamdera - Martin Stewart |date=2021-07-23 |last=Elm Online Meetup |access-date=2025-03-27 |via=YouTube}}</ref><ref>{{Cite web |title=Episode 38: Lamdera |url=https://elm-radio.com/episode/lamdera/ |access-date=2025-03-27 |website=Elm Radio Podcast |language=en}}</ref> Czaplicki has also teased Elm Studio, a potential alternative to Lamdera, but it isn't available to the public yet.<ref>{{Cite web |title=Elm Studio |url=https://www.elm.studio/ |access-date=2025-03-27 |website=www.elm.studio}}</ref> Current speculation is that Elm Studio will use a future version of Elm that targets C, uses Emscripten to compile to WASM, and supports type-safe [[Postgres]] table generation.<ref>{{Cite web |date=2021-11-03 |title=Status Update - 3 Nov 2021 |url=https://discourse.elm-lang.org/t/status-update-3-nov-2021/7870/3 |access-date=2025-03-27 |website=Elm |language=en}}</ref><ref>{{Cite web |last=Cesarini |first=Francesco |date=22 May 2023 |title=@evancz tempting the demo gods… |url=https://xcancel.com/FrancescoC/status/1660591792780111872 |access-date=26 March 2025 |website=[[Twitter]]}}</ref>
For full-stack frameworks, as opposed to [[Backend as a service|BaaS]] products, elm-pages is perhaps the most popular fully open-source option.<ref>{{Cite web |title=elm-pages - pull in typed elm data to your pages |url=https://elm-pages.com/ |access-date=2025-03-27 |website=elm-pages |language=en}}</ref> It does not extend the Elm language, but just runs the compiled JS on [[Node.js]]. It also supports scripting. There is also Pine, an Elm to .NET compiler, which allows safe interop with C#, F#, and other [[Common Language Runtime|CLR]] languages.<ref>{{Cite web |title=Pine — Run Elm Everywhere |url=https://pine-vm.org/ |access-date=2025-03-27 |website=pine-vm.org}}</ref>
There were also some attempts in Elm versions prior to 0.19.0 to use the [[BEAM (Erlang virtual machine)]] to run Elm, but they are stuck due to the removal of native code in 0.19.0 and changes to the package manager. One of the projects executed Elm directly on the environment,<ref>{{Cite web |url=https://github.com/hkgumbs/elm-beam |title=Kofigumbs/Elm-beam |website=[[GitHub]] |date=24 September 2021}}</ref> while another one compiled it to Elixir.<ref>{{Cite web |url=https://github.com/wende/elchemy |title=What is it? |website=[[GitHub]] |date=24 September 2021}}</ref>
Finally, the Gren programming language started out a fork of Elm primarily focused on backend support, although its goals have since shifted.
== The Elm Architecture (TEA pattern) ==
Line 75 ⟶ 82:
Elm does not support [[Type class#Higher-kinded polymorphism|higher-kinded polymorphism]],<ref>{{cite web |title=Higher-Kinded types Not Expressible? #396 |url=https://github.com/elm-lang/elm-compiler/issues/396 |website=github.com/elm-lang/elm-compiler |access-date=6 March 2015}}</ref> which related languages [[Haskell]], [[Scala (programming language)|Scala]] and [[PureScript]] offer, nor does Elm support the creation of [[type class]]es.
This means that, for example, Elm does not have a generic <code>map</code> function which works across multiple data structures such as <code>List</code> and <code>Set</code>. In Elm, such functions are typically invoked qualified by their module name, for example calling <code>List.map</code> and <code>Set.map</code>. In Haskell or PureScript, there would be only one function <code>map</code>. This is a known feature request that is on
Another outcome is a large amount of [[boilerplate code]] in medium to large size projects as illustrated by the author of "Elm in Action," a former Elm core team member, in
== Example code ==
| |||