Shout out to D at cppcon, when talkign about ranges.

[John Colvin via Digitalmars-d]

On Wednesday, 7 October 2015 at 17:13:45 UTC, Jonathan M Davis 
wrote:
> As I understand it, there are algorithms that inherently need 3 
> iterators to do whatever is they do, and the question of how to 
> deal with them has come up before in the newsgroup. I think 
> that it's pretty clear that such algorithms are relatively few 
> in number, but they do exist, and solving them with ranges does 
> get potentially awkward. Similarly, using iterators with 
> containers when you have to pass them to the container 
> generally works better than ranges do. We've had to add 
> overloads to  the std.container types which take the results of 
> the various take functions in order to work around that 
> problem. So, there are clearly cases where ranges become 
> awkward and iterators aren't.
>
> On the other hand, when dealing with algorithms, ranges tend to 
> be far cleaner - especially when you need to chain them. And 
> they tend to form a better basis of how to think about 
> algorithms (even when dealing with iterators, you pretty much 
> have to think in terms of ranges on some level at least). And 
> ranges handle laziness far better than iterators do. So, I'm 
> not the least bit convinced that iterators are a better way to 
> go (quite the opposite), and I'm not convinced that trying to 
> mix iterators and ranges is at all a good idea. But I do think 
> that it's clear that using only ranges is not without its 
> downsides, and since we're the first folks to seriously use 
> ranges heavily in a language or standard library, we're bound 
> to be making mistakes due to inexperience. At this point, I 
> would guess that trying to mix iterators and ranges is just 
> going to over-complicate things in an already over-complicated 
> language, but it may actually be a big win for the C++ folks. 
> We'll have to wait and see.
>
> If we _were_ to look at doing something more than straight 
> ranges, we'd probably look more at something like Steven's 
> cursors than adding iterators, though I think that there's a 
> decent chance that that only really helps with containers (it's 
> been a while since I looked at what he did with cursors, and I 
> really don't remember the details), though for the most part, I 
> think that containers are the primary place where ranges tend 
> to get annoying. Algorithms where they're problematic do exist, 
> but they seem to be rare.
>
> - Jonathan M Davis

Couldn't we define a TriRange or something for this?