Some time ago I put together quarter-baked genetic algorithm tool in Common Lisp. It dynamically generated functions in an attempt to create a modelling function for a sequence of (x,y) pairs.

Good functions would be recombined with other good functions to attempt to get better. It worked fairly well for the trivial stuff I was doing.

Unfortunately, due to getting interrupted and put down for months, it's a mess. I should fix it up tomorrow since I'll have some free time. :-)