genetic programming

In artificial intelligence, genetic programming (GP) is an evolutionary algorithm-based methodology inspired by biological evolution to find computer programs that perform a user-defined task. Essentially GP is a set of instructions and a fitness function to measure how well a computer has performed a task. It is a specialization of genetic algorithms (GA) where each individual is a computer program. It is a machine learning technique used to optimize a population of computer programs according to a fitness landscape determined by a program's ability to perform a given computational task.

Is this really a real thing? how do you even generate and mutate programs?

I found this http://www.cleveralgorithms.com/nature-inspired/evolution/genetic_programming.html
and made this http://bpaste.net/show/drTCe5TOehrzekcopfEz/
adding the 'if' macro and changing the target function to abs(x)
(if a b c d) works as: if (a<b) c, else d

and got this:
done! Solution: f=0, (if (- (- x 2) (- -2 x)) (* 1 x) (- (/ (- x x) x) x) x)

pretty neat, what's the next step?