anchor.diff:  ;; => 15
   ----
   
  -You can observe that in case of `foldl` is identical to the clojure `reduce` function:
  +You can observe that `foldl` is identical to the clojure `reduce` function:
   
   [source, clojure]
   ----
  
positive.code: 
  === Foldable
  
  The *Foldable* is generic abstraction of fold operations on a data structure. It consists
  mainly on two functions: `foldl` and `foldr`. The `foldl` is also known as `reduce`
  or `inject` in other mainstream programming languages.
  
  
  The both function consists in a identical signature and differes on how them traverse
  the data structure. Let's take a `foldl` for a little example:
  
  [source, clojure]
  ----
  
negative.code: 1⊕(2⊕(3⊕(4⊕(5⊕(wc)))))
  ----
  
  In languages with strict argument evaluation, `foldr` does not have many
  applications because when the data structure to fold grows it tends to consume all the
  stack (causing the well known stack overflow). In case of Clojure, the unique obvious
  case of using foldr is for small datastructures or lazy sequences.
  