Wikipedia has some notes on the difference:

http://en.wikipedia.org/wiki/AVL_tree

AVL has faster lookup, so maybe they decided to optimise for that.

It's different to some other languages I've seen, but then so is their decision to not use a tail recursive List.map. Each to their own, it's not hard to implement the alternative :)


On Mon, Jun 2, 2014 at 11:21 PM, Damien Guichard <alphablock@orange.fr> wrote:

 
Red-black tree would spare a machine word per node, because a red-black tree doesn't need depth information. 
Hence the reason is either historical or a space/speed trade-off (comparing two depths may be faster than pattern matching). 
 
Regards,
 
damien guichard 
Hi, list,

Just from the curiosity, why balanced binary trees used in Set and Map are AVL-trees, not their alternative, say, red-black trees?  Is there a deep reason for it, or just a historical one?

Best,
--
Yoriyuki Yamagata
http://yoriyuki.info/