Clean (programming language)
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|Usual file extensions||.icl, .dcl, .abc, .obj|
|Designed by||Software Technology Research Group of Radboud University Nijmegen|
|Stable release||2.2 (December 18, 2006)|
|Typing discipline||strong, static, dynamic|
|Influenced by||Lean, Haskell|
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's method for dealing with mutable state and I/O is done through a uniqueness typing system, in contrast to Haskell's use of monads. "The uniqueness type system also allows the Clean compiler to generate efficient code because uniquely attributed data structures can be destructively updated."
Start = "Hello, world!"
fac 0 = 1 fac n = n * fac (n-1) // find the factorial of 10 Start = fac 10
fib 0 = 0 fib 1 = 1 fib n = fib (n - 2) + fib (n - 1)
Start = fib 7
(^) 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.
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.
- 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.
The syntax of Clean is very similar to Haskell, with some notable differences.
|(a -> b) -> [a] -> [b]||(a -> b) [a] -> [b]||higher order function|
|f . g||f o g||function composition|
- Clean homepage
- Clean in FOLDOC
- Clean in The Computer Language Benchmarks Game
- Clean vs. Haskell discussion (haskell-cafe)
- Clean FAQca:Clean