anchor.diff:  ;; => (2 3 4)
   ----
   
  -But why fmap works with vectors? Some "container" types of clojure like vectors, lists or sets
  -also implements the functor abstraction.
  +But why fmap works with vectors? Because some "container" types of clojure like vectors,
  +lists or sets also implements the functor abstraction.
   
   
   Applicative
  
positive.code: ;; => #<Either [:bar :right]>
  ----
  
  Possible you will understand the purpose and use case of **pure** function in
  the next section: *Monad*.
  
  Monad
  ~~~~~
  
negative.code: ----
  [cats "0.2.0-SNAPSHOT"]
  ----
  
  
  Maven
  ~~~~~
  