In this case, "function" means mathematical function rather than purpose. Of course, if you want to take a somewhat reductionist approach, you could argue that

In this case, "function" means mathematical function rather than purpose. Of course, if you want to take a somewhat reductionist approach, you could argue that data structures are functions. After all, in the lambda calculus, all you have are functions and you can use them represent numbers, pairs, lists, booleans, conditionals--basically whatever you want.