opIndex, opSlice, length for joiner?

[Maverick Chardet via Digitalmars-d]

Hi everyone,

After reading the thread "Distributed Memory implementation": 
http://forum.dlang.org/post/oqcfifzolmolcvyupsef@forum.dlang.org

And more precisely the suggestion of Dragos Carp on page 2: 
http://forum.dlang.org/post/txgabyyoutitketlpvgm@forum.dlang.org

I looked at the joiner source code 
(std.algorithm.iteration.joiner) and I have several ideas to make 
it have the opIndex, opSlice and length methods under certain 
conditions.

First question: what do you think of making this possible if all 
the considered ranges have opIndex, opSlice and length? I think 
that all the ranges types don't have to all implement the three 
methods in all cases (for instance length would actually only 
require ElementType!RoR and Separator to implement length) but we 
can discuss all that later...

The most important issue that comes to my mind is that the 
operations would not take constant time... A trivial 
implementation would be in O(k) where k is the number of joined 
ranges, and with some precomputation in O(k) time and space we 
can make length O(1) and opIndex and opSlice O(log k)... Would 
that be a problem?

Thank you in advance for your remarks!