What it is

Class-mixins are a great idea but sometimes they lead to a proliferation of subclasses with names like printable-touchable-composing-colored-shape-square-mixin and that's just ugly. Common-Lisp is a dynamic-programming language; Dynamic-Classes brings dynamism to class definition!

You define the mixins and associate them with parameters. Then you

As an example, here is some code from cl-containers iterators that hooks parameters to iterator mixins:

(add-parameter->dynamic-class  
 :iterator :transform 'transforming-iterator-mixin)  
 
(add-parameter->dynamic-class  
 :iterator :filter 'filtered-iterator-mixin)  
 
(add-parameter->dynamic-class  
 :iterator :unique 'unique-value-iterator-mixin)  
 
(add-parameter->dynamic-class  
 :iterator :circular 'circular-iterator-mixin) 

and here it is in action:

> (let ((i (make-iterator '(1 2 3))))  
	    (loop repeat 5 when (move-forward-p i) do  
		 (print (next-element i))))  
1  
2  
3  
nil  
 
> (let ((i (make-iterator '(1 2 3) :circular t)))  
	    (loop repeat 5 when (move-forward-p i) do  
		 (print (next-element i))))  
1  
2  
3  
1  
2  
 
> (let ((i (make-iterator '(1 2 3) :circular t :transform #'sqrt)))  
	    (loop repeat 5 when (move-forward-p i) do  
		 (print (next-element i))))  
1.0  
1.4142135  
1.7320508  
1.0  
1.4142135 

The make-iterator function calls determine-iterator-class to handle the work of figuring how (and possibly creating) the right class given the parameters.

(defmethod make-iterator  
    (iteratee &rest args &key (iterator-class nil) &allow-other-keys)  
  (apply #'make-instance  
	 (apply #'determine-iterator-class iteratee iterator-class args)  
         :container iteratee  
         args)) 

Dynamic-Classes can make prototyping a breeze (and it's lots of fun too)!

Mailing Lists

• dynamic-classes-devel: A list for announcements, questions, patches, bug reports, and so on; It's for everything but the sinking kitchen.

Where is it

metabang.com is switching from darcs to git for source control; the current dynamic-classes repository is on github and you can clone it using:

git clone git://github.com/gwkkwg/dynamic-classes 

Dynamic-Classes is also ASDF installable. Its CLiki home is right where you'd expect.

There's also a handy gzipped tar file.

What is happening

2010 Dec 21 moved to github.

2008-May-26 We've split off from metatilities and are living large and on our own! More tests and documentation coming ... soon (we hope).