Uh, no, you're missing the point. It's always possible for you to reverse the array and read it backwards. After all, that's how you are capable of reversing it

Uh, no, you're missing the point. It's always possible for you to reverse the array and read it backwards. After all, that's how you are capable of reversing it! The problem is that the thing that you are handing it to might not be capable of that. You can't pass an array to write(2) and tell it to actually print it in reverse order. You can't mmap a page where first byte of data is actually at the high address. Your DMA engine won't flip your buffer for you. If you want to use these APIs, you have to reverse the array before you hand it to them. There's just no way around it. Also, I do want to note that just because your language is higher level and takes iterators or sequences or whatever abstraction you have on top of "a bunch of elements" doesn't actually mean that reversing an array is never worth it. It is often the case that your API/compiler/language will support passing in an arbitrary "view", but if you actually try to do this you will find that it can only fully reason about the "forward, contiguous" buffer case, which it will optimize well. If you pass it anything funny it will fall back to the element-by-element code which can be an order of magnitude slower, or more (usually this means no vectorization, for example). In this case it's often better to pull out an optimized reverse and then pass a normal array to the API. Even though it would read the data twice this can still be a lot faster.