Ropes (concatenation trees) for strings in D ?

[Carl Sturtivant via Digitalmars-d-learn]

This is the idea I mean.
http://citeseer.ist.psu.edu/viewdoc/download?doi=10.1.1.14.9450&rep=rep1&type=pdf
Here's a C++ implementation supported I think by gcc.
http://www.sgi.com/tech/stl/Rope.html

Is there a D implementation of a rope out there somewhere?

How is unicode handled? Just by using dchar?