Ropes

[sybrandy]

Not sure if this is what's used by an Appender, but this seems like a 
cool data structure:

http://ahmadsoft.org/ropes/

http://en.wikipedia.org/wiki/Rope_%28computer_science%29

It's not good for indexing, but concatenation is an O(1) operation, so 
using it when you have to do a lot of appending seems to make a lot of 
sense.  And, if I understand appender correctly, it's meant only for 
appending data and that you need to convert it to a range/array before 
you work with it.

Casey