Nilsimsa is a distance based hash, which is the opposite of more familiar hashes like MD5. Instead of small changes making a large difference in the resulting hash (to avoid collisions), distance based hashes cause similar values to have similar output. This is good for detecting near similar documents without having to store the original text.
Standard usage is as follows:
require 'nilsimsa'
n1 = Nilsimsa::new text1 = "The quick brown fox" n1.update(text1) puts "Text '#{text1}': #{n1.hexdigest}"