anchor.diff:          state
   
       // TODO :
  +    // choosei
       // foldPairs, foldBackPairs
       // derive    // takes a 'T -> 'T -> 'T like reduce, but only performs one step; used to perform 'divided differences'
           // Other possible names: reduceOnce, reduceStep
  
positive.code: 
      (* TODO
  
      Seq.segment
          Groups elements of a sequence together "longitudinally" -- i.e., it works
          in a streaming fashion, rather than Seq.groupBy which needs to see the
  
negative.code: 
      (* TODO
  
      List.choosei
  
      List.unzipMap
          Similar to List.map2 (and List.zipMap, below). Given a list of tuples (a, b)
          applies the elements of each tuple to a function 'f' (f a b).
  