I'm reading the introduction to Godel, Escher, Bach and and there's heavy discussion of mathematical sets which contain themselves. Being a far better programmer than mathematician, I put it into terms I'm more comfortable with and started to think about arrays which contain/reference themselves.
I know that recursion is a very powerful concept in CS but that it's typically manifested through functions which call themselves. I see recursive functions in algorithms all the time, but I've never before run across an array that has itself as an element. I was just wondering if there's any particular "usefulness" or practical application for arrays which contain themselves (as there is for functions which call themselves).