[stcredzero]

Well, I have to use OpenGL for my development, and it's a giant state machine that works mainly via side-effects. It's notoriously frustrating to work with, but that's life. I realize not all code works that way, but I'd bet the majority of code does.

I suspect your sample is a bit skewed.

The Smalltalk class library wasn't stateless. It certainly wasn't pure. Really, code only has to be "pretty good" for such techniques to work well.