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
xx^(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
# 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.
Platforms
Clean is available for
Windows
But with limited input-output capabilities and without the "Dynamics" feature prior to version 2.2 for the following platforms:
Macintosh
Solaris
Linux
License
Clean is
dual licensed: it is available under the terms of the
GNU LGPL, and also under a proprietary license for €75.