AVL Trees V1.0
24-July-1987
Paul Vixie

This library and test program are useful for creating and using balanced
binary trees (AVL trees).  The tree is held in memory, using malloc(3) to
allocate storage.  A better version would allow file-based trees in 
addition; once memory mapped files hit the UNIX(tm) community, this will
be much easier to do.  In the meanwhile, these routines have been very
useful to be for symbol tables and the like.  (Yes, I'm sure hashing is
better in some way, but I've used this for symbol tables, just the same.)

I cannot take credit for the algorithms.  See "Algorithms & Data Structures,"
Niklaus Wirth, Prentice-Hall 1986, ISBN 0-13-022005-1.  This is an update of
Wirth's previous book, titled "Algorythms + Data Structures = Programs,"
which used Pascal as the language for examples.  This later book uses the
newer Modula-2 for it's examples; this tree code was created using the
Modula-2 examples as guidelines.  At the time I typed this stuff in (about
a year ago, in July 1987), I understood how it all worked.  Today, well...

This code is hereby placed in the public domain, unless restrictions apply
from Prentice-Hall on the algorithms themselves.  If you use or redistribute
this code, please leave my name (and Wirth's) in the comments.