That's a fair point about map being constrained in the top-level structure of what it returns, but what map actually does depends on the function that is being mapped, and includes the possibility of more than one operation at a time - and if your language allows side-effects it can do that too. The point is that you have to look at the 'blah, blah, blah' to know what is happening (actually, the point of my original post is about extravagant claims of what simple examples demonstrate...)