Clean (programming language)
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| Usual file extensions | .icl, .dcl, .abc, .obj |
|---|---|
| Paradigm | functional |
| Appeared in | 1987 |
| Designed by | Software Technology Research Group of Radboud University Nijmegen |
| Latest release | 2.2/ 2006-12-18 |
| Typing discipline | strong, static, dynamic |
| Influenced by | Lean, Haskell |
In computer science, Clean is a general-purpose purely functional computer programming language.
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[edit] Features
The language Clean first appeared in 1987 and is still further developed; it shares many properties with Haskell: referential transparency, list comprehension, guards, garbage collection, higher order functions and currying and lazy evaluation.
An integrated development environment (IDE) is included in the Clean distribution.
Clean has an alternative to monads, which are regular in the Haskell language; a uniqueness typing system deals with unduplicatable resources such as input and output.
[edit] Examples
module hello
Start = "Hello, world!"
module factorial
fac 0 = 1 fac n = n * fac (n-1) // find the factorial of 10 Start = fac 10
module fibonacci
fib 0 = 0 fib 1 = 1 fib n = fib (n - 2) + fib (n - 1)
Start = fib 7
Infix operator:
(^) infixr 8 :: Int Int -> Int (^) x 0 = 1 (^) x n = x * x ^ (n-1)
The type declaration states that the function is a right associative infix operator with priority 8: this states that x*x^(n-1) is equivalent to x*(x^(n-1)) as opposed to (x*x)^(n-1); this operator is pre-defined in the Clean standard environment.
[edit] How Clean works
Computation is based on graph rewriting and reduction. Constants such as numbers are graphs and functions are graph rewriting formulas. This, combined with compilation to native code, makes Clean programs relatively fast, even with high abstraction.
[edit] Compiling
- Source files (.icl) and project files (.dcl) are converted into Clean's platform-independent bytecode (.abc), implemented in C and Clean.
- Bytecode is converted to object code (.obj) using C.
- object code is linked with other files in the module and the runtime system and converted into a normal executable in Clean.
Earlier Clean system versions were written completely in C, thus avoiding bootstrapping issues.
[edit] Platforms
Clean is available for Microsoft Windows. It is also available with limited input/output capabilities and without the "Dynamics" feature for Apple Macintosh, Solaris and Linux.
[edit] License
Clean is dual licensed: it is available under the terms of the GNU LGPL, and also under a proprietary license.
[edit] Versus Haskell
[edit] Speed
Some state that Clean is faster than Haskell,[1] but other researches show that this depends on the kind of program that is tested.[2]
[edit] Syntactic differences
Although the syntax of Clean and Haskell is almost the same, these are some differences:[3]
| Haskell | Clean | Remarks |
|---|---|---|
| (x:xs) | [x:xs] | list construction |
| (a -> b) -> [a] -> [b] | (a -> b) [a] -> [b] | |
| f . g | f o g | function composition |
| -5 | ~5 | unary minus |
