anchor.diff:  
   == Introduction
   
  -This is an implementation of functional references modeled as functions (in the
  -same way as transducers).
  -
  -Functional reference or lense is a generalization of get and put mapping to the
  -particular part of a data structure, where the result is called _view_ or _focus_
  -and the container is usually called _source_.
  +This is an implementation of functional references modeled as functions (in the same
  +way as transducers). Is a generalization of get and put mapping to the particular
  +part of a data structure.
  +
  +Please, see <<quick-start, Quick Start>> section in order to understand it better
  +seeing some example code.
   
   NOTE: This documentation does not covers all api, so if you miss some function,
   contributions are very welcome. You can see the full link:api/index.html#id[API documentation here].
  
positive.code: ----
  
  
  === Lenses composition
  
  One of the big advantatges of the lenses implementation of cats library is that
  them are implemented using plain functions:
  
  [source, clojure]
  ----
  (def my-lens (comp l/fst l/fst (l/nth 2)))
  
  (def data
    [[0 1 2]
     [3 4 5]])
  
  (l/focus my-lens data)
  ;; => 2
  
  (l/put my-lens 42 data)
  ;; => [[0 1 42] [3 4 5]]
  ----
  
  Lenses compose with regular function composition and, like transducers, the
  combined lens runs from left to right.
  
  
  === Builtin lenses
  
  There's `key` and `select-keys` for focusing on one or multiple keys respectively:
  
  
negative.code: ----
  
  
  === Composition
  
  One of the big advantatges of this lenses implementation is because it is
  implemented in termps of function composition, much in the same line as
  transducers. Let see a example:
  
  [source, clojure]
  ----
  (def my-lens (comp l/fst l/fst (l/nth 2)))
  
  (def data
    [[0 1 2]
     [3 4 5]])
  
  (l/focus my-lens data)
  ;; => 2
  
  (l/put my-lens 42 data)
  ;; => [[0 1 42] [3 4 5]]
  ----
  
  Lenses compose with regular function composition and, like transducers, the
  combined lens runs from left to right.
  
  
  == Developers Guide
  