anchor.diff:  (m/fmap inc [1 2 3 4])
   ;; => [2 3 4 5]
   ----
  +
   
   ==== nil
   
  
positive.code:            (maybe/nothing))
  ;; => #<Just [1 2 3 4 5 6]>
  ----
  
  === Functor
  
  
negative.code: 
  Also, since `mlet` desugars into calls to the Monad's `bind` function, its result keeps the type of the monadic values.
  
  
  ==== Lazy sequences
  
  Lazy sequences implement the same abstractions as vectors with practically an identical implementation. If you don't need
  