anchor.diff:  
   ifdef::env-github,env-browser[:outfilesuffix: .adoc]
   
  -== Versions
  -
  -This document was written while checking the details against Clojure 1.7  and Java 6,
  -but most or all of it should apply to other versions, too.
  +_Note: This document describes Clojure 1.7 and Java 6, but applies to most other versions as well._
   
   == Summary
   
  
positive.code:   (<= (second a) (second b)))
  ----
  
  The boolean comparator _by-2nd-<=_ seems to work correctly on the first step of creating the set,
  but fails when testing whether elements are in the set.
  
  [source, clojure]
  
negative.code: ----
  
  You can see this by calling the compare method of any Clojure function.
  Below is an example with a custom version `my-<` of `<` that prints its arguments when it is called,
  so you can see the cases where it is called more than once:
  
  [source, clojure]
  