The data structure has great complexity, and is closely relate to hash-array mapped tries, and ropes, which have good implementations. Individual implementatio

The data structure has great complexity, and is closely relate to hash-array mapped tries, and ropes, which have good implementations. Individual implementations might suck. Others are just fine (http://hackage.haskell.org/packages/archive/fingertree/0.0/doc/html/src/Data-FingerTree.html#FingerTree http://hackage.haskell.org/packages/archive/fingertree/0.0/d...) - though even this could be optimized (for constant factors).