anchor.diff:  
     /* Return the last element of a list.
   
  +     This function throws an error if the list is empty.
  +
  +     Type: last :: [a] -> a
  +
        Example:
          last [ 1 2 3 ]
          => 3
  
positive.code: 
    /* Return a list of integers from `first' up to and including `last'.
  
       Example:
         range 2 4
         => [ 2 3 4 ]
         range 3 2
         => [ ]
    */
    range = first: last:
      if first > last then
        []
      else
        genList (n: first + n) (last - first + 1);
  
    /* Splits the elements of a list in two lists, `right' and
       `wrong', depending on the evaluation of a predicate.
  
       Example:
         partition (x: x > 2) [ 5 1 2 3 4 ]
  
negative.code: 
    /* Remove duplicate elements from the list. O(n^2) complexity.
  
       Type: unique :: [a] -> [a]
  
       Example:
         unique [ 3 2 3 4 ]
         => [ 3 2 4 ]
     */
  