anchor.diff:  ----
   (require '[cats.monad.maybe :as maybe])
   
  -(pure maybe/context 5)
  +(m/pure maybe/context 5)
   ;; => #<Just 5>
   ----
   
  
positive.code: 
  [source, clojure]
  ----
  (foldr (fn [v wc] (+ v wc)) 0 [1 2 3 4 5])
  ;; => 15
  ----
  
  
negative.code: 
  [source, clojure]
  ----
  (m/foldl (fn [acc v] (+ acc v)) 0 [1 2 3 4 5])
  ;; => 15
  ----
  
  