Clean programming language

From Academic Kids

Clean is a general-purpose purely functional programming language. Functional languages stress application of functions, as opposed to execution of commands, as in imperative languages.

Contents

Features

Examples

Hello world(Store as hello.icl):

module hello
Start = "Hello, world!"

Factorial:

 module factorial
fac 0 = 1 fac n = n * fac (n-1) // find the factorial of 10 Start = fac 10

Fibonacci sequence:

 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.

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.

Compiling

  1. Source files (.icl) and project files (.dcl) are converted into Clean's platform independent bytecode (.abc), implemented in C and Clean.
  2. Bytecode is converted to object code (.obj) using C.
  3. 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.

Platforms

Clean is available for

License

Clean is licensed under the GNU LGPL, but can be used without the LGPL if bought for €495.

See also

External links

  • Clean in FOLDOC (http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?Clean)
  • Clean performs pretty well in the Computer Language Shootout Benchmarks (http://shootout.alioth.debian.org/great/benchmark.php?test=all&lang=all&lang2=clean&sort=fullcpu) - though the value of such benchmarks can be debated.pt:Clean

zh:Concurrent Clean de:Clean

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