anchor.diff:  quicksort can readily handle numbers, strings, or lists of chars, all
   thanks to the power of this line right here:
   
  -[code,haskell]
  +[source,haskell]
   ----
   quicksort :: (Ord a) => [a] -> [a]
   ----
  
positive.code: semantically it's _almost_ identical [but not quite, and I'll get to
  why]).
  
  [code,scheme]
  ----
  (define (qs lst)
    (if (empty? lst)
  
negative.code: 
  For reference, the Haskell recursive quicksort looks like this:
  
  [source,haskell]
  ----
  quicksort :: (Ord a) => [a] -> [a]
  quicksort [] = []
  