From: Joel VanderWerf <vjoel@...>
Date: 2003-12-09T16:56:17+09:00
Subject: Re: handling large data sets

Martin Pirker wrote:
> looking at the README of rbtree, the extra methods "lower_bound,
> upper_bound" (and others?) provided by rbtree don't seem to be
> mentioned - is there a docu explaining them or guess from the test code?

irb(main):002:0> t = RBTree.new
=> #<RBTree: {}, default=nil, compare=nil>
irb(main):003:0> t[1] = "one"
=> "one"
irb(main):004:0> t[4] = "four"
=> "four"
irb(main):005:0> t[7] = "seven"
=> "seven"
irb(main):006:0> t.lower_bound(3)
=> [4, "four"]
irb(main):007:0> t.upper_bound(3)
=> [1, "one"]

So my guess is lower_bound is the "greatest lower bound" for the set of 
keys above the argument.

http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?greatest+lower+bound