faster splitter

[qznc via Digitalmars-d]

On Monday, 23 May 2016 at 12:01:52 UTC, qznc wrote:
> Additionally, there is this weird special case for a 
> bidirectional range, which just adds unnecessary overhead. Is 
> "remove dead code" a good enough reason in itself for a PR?

Forget the "dead code comment" it is a actually a missing 
feature. In the case the separator is a range and the input range 
is bidirectional, the splitter result should be bidirectional as 
well. It is not, because the implementation of back() and 
popBack() is missing, although some bookkeeping code for it 
exists.