Slate | sykosomatic

In the last entry, I wrote a bit about the basics of how object instantiation and property/slot access works in Sheeple. In this entry, I’ll introduce a whole different realm of Sheeple: the method dispatch system. If you’re familiar with Javascript, it might already be obvious to you how polymorphic method dispatch can be implemented with the small bit of Sheeple we know so far:

SHEEPLE-USER> (add-property *sheep* 'foo
                            (lambda ()
                              (print "Method called!")))
#<Sheep #x15031356>
SHEEPLE-USER> (foo *sheep*)
#<Anonymous Function #x1506C446>

For those confused: the above equivalent in javascript would be:

sheep.foo = function () { alert("Method called!"); }
sheep.foo -> function object

And there you have it. Actually calling the function is just a matter of using Lisp’s version of adding () at the end of a variable:

SHEEPLE-USER> (funcall (foo *sheep*))
"Method called!"

In JS:

sheep.foo(); => an alert pops up. The method was called.

For a few months now, I’ve been working on something I call Sheeple. What is Sheeple? From the
official description:

Sheeple is a Dynamic, CLOS-like, Delegative Prototype-based Object-Oriented Programming
Framework (or “POOP Framework”) that strives to optimize application flexibility, minimize cost
while increasing value, maximize programmer resources, and empower application implementers to
better assist them in leveraging modern paradigms in order to proactively achieve next-generation
synergy in tomorrow’s web 3.0 world. It is implemented in (mostly) ANSI Common Lisp. Sheeple is
fully buzzword compliant.

Now that doesn’t really say much of anything, but it’s
amusing, specially since some actual (professional!) projects actually describe things in such a
way.

What does it actually do, though?

Well, Sheeple is a library for Common Lisp that implements a Prototype-based object-oriented language very similar to Common Lisp’s standard CLOS. It does things like multiple dispatch, multiple inheritance and such.

One goal I had while designing it was to have it be as practical as possible. Javascript is making waves around the internet these days — not just because it’s the de-facto standard browser-scripting language, but because it’s prototype-based.

The idea of having a prototype-based language instead of using classes for OO is nothing new. Even so, it seems like there’s still debate about the merits of using prototypes instead of classes. In fact, some prototype-based languages, specifically Javascript, have libraries that implement classes!

Even though there are various languages to choose from, there are still few languages that provide what I would consider full facilities. Cecil seems to be one of those ‘full’ languages, but I really ended up disliking its approach — it was too complicated, and there were too many obvious minefields. Sheeple is an attempt at providing the kind of massive framework CLOS provides for class-based OO, but with prototypes, while remaining easy-to-use, straightforward, and most importantly, convenient. Whether it’s successful at this right now (it’s still in development after all), and whether it will ever be is a different question. ;)
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