Clean - Programming language

Clean is a programming language created in 1987.

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37Years Old

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Clean is a general-purpose purely functional computer programming language. For much of the language's active development history it was called Concurrent Clean, but this was dropped at some point.. Read more on Wikipedia...

Clean website
Clean Wikipedia page
Clean docs
There are at least 206 Clean repos on GitHub
Clean first developed in Radboud University Nijmegen
The Google BigQuery Public Dataset GitHub snapshot shows 231 users using Clean in 263 repos on GitHub
Explore Clean snippets on Rosetta Code
Clean on HOPL
Clean appears in the TIOBE Index
Pygments supports syntax highlighting for Clean
GitHub supports syntax highlighting for Clean
See also: (7 related languages)Miranda, Haskell, C, Solaris, Linux, Fibonacci, Prolog

Example from Compiler Explorer:

module example

import StdInt

square :: Int -> Int
square n = n * n

Start :: Int
Start = square 3

Example from Riju:

module main

import StdEnv

Start world
  #(console, world) = stdio world
  #console = fwrites "Hello, world!\n" console
  #(ok, world) = fclose console world
  = world

Example from hello-world:

module hello
Start :: {#Char}
Start = "Hello World"

Example from the Hello World Collection:

// Hello World in Clean

module hello

Start :: String
Start = "Hello World!\n"

Example from Linguist:

definition module GenMap

import StdGeneric

generic gMap a b :: .a -> .b
derive gMap c, UNIT, PAIR, EITHER, CONS, FIELD, OBJECT, {}, {!}

derive gMap [], (,), (,,),  (,,,), (,,,,), (,,,,,), (,,,,,,), (,,,,,,,)

Example from Wikipedia:

(^) infixr 8 :: Int Int -> Int
  (^) x 0 = 1
  (^) x n = x * x ^ (n-1)

Clean Keywords

case ccall class code code inline derive export foreign generic if in infix infixl infixr instance let of otherwise special stdcall where with

Language features

Feature	Supported	Token	Example
Conditionals	✓
Classes	✓
Strings	✓	"	"Hello world"
Line Comments	✓	//	// A comment
Comments	✓
Semantic Indentation	X