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Erlang is a functional, concurrent programming language created at Ericsson in 1986 by Joe Armstrong, Robert Virding, and Mike Williams to build highly reliable telephone switching systems. It is built around lightweight processes, message passing, and the actor model, with no shared mutable state. Erlang excels at fault-tolerant, distributed, soft real-time systems and popularized the 'let it crash' philosophy backed by supervision trees.
On CompileBytes, Erlang runs on the BEAM virtual machine via Erlang/OTP, reported as version 23.0.0. OTP (Open Telecom Platform) bundles libraries and design principles for building robust applications. Erlang powers messaging platforms, telecoms, databases, and high-availability backends, and it is known for hot code swapping and the ability to run millions of concurrent processes with very low overhead.
main.erl is the entry point for each run.
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-module(main).
-export([start/0]).
start() ->
io:format("Hello, World!~n").-module(main).
-export([start/0]).
square(N) -> N * N.
start() ->
io:format("~p~n", [square(5)]).-module(main).
-export([start/0]).
fact(0) -> 1;
fact(N) when N > 0 -> N * fact(N - 1).
start() ->
io:format("~p~n", [fact(6)]).-module(main).
-export([start/0]).
start() ->
Pid = spawn(fun() -> io:format("Hello from process~n") end),
io:format("Spawned ~p~n", [Pid]).-module(main).
-export([start/0]).
sum([]) -> 0;
sum([H | T]) -> H + sum(T).
start() ->
io:format("~p~n", [sum([1, 2, 3, 4, 5])]).-module(main).
-export([start/0]).
start() ->
Squares = [X * X || X <- [1, 2, 3, 4, 5]],
io:format("~p~n", [Squares]).-module(main).
-export([start/0]).
classify(N) ->
case N of
0 -> zero;
_ when N > 0 -> positive;
_ -> negative
end.
start() ->
io:format("~p~n", [classify(-4)]).-module(main).
-export([start/0]).
area({circle, R}) -> 3.14159 * R * R;
area({rectangle, W, H}) -> W * H.
start() ->
io:format("~p~n", [area({rectangle, 3, 4})]).-module(main).
-export([start/0]).
start() ->
Doubled = lists:map(fun(X) -> X * 2 end, [1, 2, 3]),
Total = lists:foldl(fun(X, Acc) -> X + Acc end, 0, Doubled),
io:format("~p ~p~n", [Doubled, Total]).The editor uses Monaco, the engine behind VS Code, with language-aware editing tools and familiar keyboard controls.
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Erlang is one of 46 single-file compiler scratchpads. Each run submits only main.erl; local sibling-file imports are not enabled.
Linked-project languages (23): Node.js, TypeScript, Deno, Python, C, Go, Dart, Swift, Rust, Ruby, PHP, Java, Kotlin, C++, C#, Nim, Crystal, Haxe, Zig, Scala, D, Bun, Objective-C.
Single-file scratchpads (46): Matplotlib, NumPy, pandas, Haskell, Clojure, Perl, Lua, Tcl, jq, Raku, Elixir, Bash, Zsh, Nushell, R, Assembly (NASM), Julia, Octave, Groovy, PowerShell, Visual Basic .NET, Odin, Pascal, Lisp, Erlang, CoffeeScript, COBOL, BASIC, V, Racket, OCaml, Prolog, AWK, Emacs Lisp, Emojicode, Forth, F#, Fortran, Assembly (NASM64), Solidity, Mojo, Ada, WASM (WAT), Gleam, Shell Script (sh), Scheme.
Download file exports the active Erlang source file.