Transience of .front in input vs. forward ranges

[Jonathan M Davis]

On Sunday, November 04, 2012 20:59:16 H. S. Teoh wrote:
> It lets us add code only where transience matters, which is with things
> like byLine, and a few algorithms that actually care to take advantage
> of transient ranges. Nothing else is affected. It certainly doesn't
> affect "everything" -- if indeed, as you say, transient ranges are rare
> occurrences.

The problem is that every single range-based function in Phobos which could 
possibly work with a transient range would have to take such ranges into 
account in the ranges that they create. Otherwise, the transience is lost, 
making transient absolutely useless. So, it affects a _lot_ more than just 
ranges like ByLine and ByChunk, and regardless of how rare such ranges are, 
the entirety of Phobos would have to take them into account whenever a wrapper 
range is created.

If you don't care about wrapper ranges propagating the transient property when 
they can, then there's no point in having it in the first place. You might as 
well just use opApply. And if you _do_ care, then it affects everything, even 
if base ranges with transient fronts are rare. I don't see how you can 
possibly think that this isn't a highly intrusive change to ranges.

- Jonathan M Davis