Clean programming language

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

= Features =

Referential transparency - a function, given the same inputs, always gives the same output.

Uniqueness type - easily and functionally deal with unduplicatable resources such as input and output without Monads_in_functional_programming

List comprehension - compact, powerful list generation syntax

Guard (computing)s for clear, concise conditionals

Easy-to-use Clean Integrated development environment.

Portability is almost always a simple recompile to support another platform, due to the high level of abstraction.

Automatic garbage collection - one less thing to worry about

Higher order functions and Currying

Lazy_evaluation#Delayed_evaluation support allows infinite data structures

= Examples =

hello world program(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#Mathematics_and_Computer_science 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 (complexity). 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 =

# Source files (.icl) and project files (.dcl) are converted into Clean s platform independent bytecode (.abc), implemented in C programming language 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.

= Platforms =

Clean is available for

Microsoft Windows

Apple Macintosh

Solaris Operating Environment

Linux, but with limited input-output capabilities

= License =

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

= See also =

Haskell programming language

List of functional programming topics

=External links=

*[http://www.cs.kun.nl/~clean/ Clean homepage] **[http://www.cs.kun.nl/~clean/CleanExtra/report20/contents.html Clean 2.0 Language Report] in HTML **[http://www.cs.kun.nl/~clean/contents/Clean_Book/clean_book.html An introductory textbook to Clean] *[http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgiClean Clean in FOLDOC] *Clean performs pretty well in the [http://shootout.alioth.debian.org/ Computer Language Shootout Benchmarks] - though the value of such benchmarks can be debated.