I always wanted to do this, to define a grammar and generate expressions of the generated language while driving the whole process by evolution. I did similar things before, but this one is kind of special, it is indeed a grammar in that script.
Well, here is the video showing how it looks like. It is very interesting to watch, to try to figure out what happens and why. One tries to understand the rules, what are the easy mutations, what are the hard ones. How could it be made better, make it evolve faster, go higher, to make longer programs, solve bigger equations. So check it out, does it reach 100% at the end?
You might want to take a look at the script itself. Well, I tried, but when I insert the code, no matter how, the blog engine goes haywire about it. So I attached it to this article. Well, I could rant about the blog engine and about web UI and such, but this was going to be a short thing about a grammar so I shouldn't.