anchor.diff:  In general, be wary of comparing only parts of values to each other. Consider having some kind of tie-breaking
   condition after all of the fields of interest to you have been compared.
   
  -Aside: If you do not want multiple vectors in your set with the same number, _by-2nd_ is the comparator you should use.
  -It gives exactly the behavior you want. (TBD: Are there any caveats here? Will _sorted-set_ ever use _=_ to compare elements
  +Aside: If you do not want multiple vectors in your set with the same number, `by-2nd` is the comparator you should use.
  +It gives exactly the behavior you want. (TBD: Are there any caveats here? Will `sorted-set` ever use `=` to compare elements
   for any reason, or only the supplied comparator function?)
   
   === Beware using subtraction in a comparator
  
positive.code: user> (sort #(compare %2 %1) [4 3 2 1])
  ----
  
  _reverse-cmp_ will also work for all other types _compare_ works for.
  
  === Multi-field comparators
  
  Because equal-length Clojure vectors are compared lexicographically, they can be used to do multi-field
  sorting on values like maps or records. This only works if the fields are already sorted by _compare_
  in the order you wish (or the reverse of that).
  
  Firs we will show a way to do it that does not compare vectors.
  
  [source,clojure]
  ----
  
negative.code: 
  ifdef::env-github,env-browser[:outfilesuffix: .adoc]
  
  _Note: This document describes Clojure 1.7 and Java 6, but applies to most other versions as well._
  
  == Summary
  
  