anchor.diff:  ; combined functor is a vector of Maybe values that could
   ; contain a value of any type.
   (fmap2 inc [(maybe/just 1) (maybe/just 2)])
  -;;=> [#<Just [2]> #<Just [3]>]
  +;;=> [#<Just 2> #<Just 3>]
   ----
   
   However, monads don't compose as nicely as functors do. We have to actually implement
  
positive.code: (require '[cats.monad.maybe :as maybe])
  
  (maybe/just 2)
  ;; => #<Just [2]>
  ----
  
  The `just` function is a constructor of Just type that is part of Maybe monad.
  
negative.code: (require '[cats.monad.maybe :as maybe])
  
  (pure maybe/maybe-monad 5)
  ;; => #<Just 5>
  ----
  
  If you do not understand the purpose of the *pure* function, the next section
  