Maybe the author was trying to avoid potential fallacies that follow that phrase around though: * If you don't have side effects, you can't do anything. * Has

Maybe the author was trying to avoid potential fallacies that follow that phrase around though: * If you don't have side effects, you can't do anything. * Haskell can do things? Then it has side-effects, so it's not functional. * Computer getting hot is a side-effect. * i++ is not a side-effect, because I intended to do it.