anchor.diff:  ;; => #<Promise [1]>
   ----
   
  -If a `promise` function receives a plain value, it returns a resolved promise with 
  -the provided plain value. If it receives an instance of `Error`, it returns a 
  +If a `promise` function receives a plain value, it returns a resolved promise with
  +the provided plain value. If it receives an instance of `Error`, it returns a
   rejected promise.
   
   And finally it also accepts a factory callback that receives two callable parameters:
  
positive.code: The `mlet` bindings are executed sequentially, waiting in each step for promise
  resolution. If an error occurs in some step, the entire composition will be
  short-circuited, returing exceptionally resolved promise. This is very similar
  to the up coming link:http://jakearchibald.com/2014/es7-async-functions/[ES7 async/await], but built in a generic way and as a library and not language feature.
  
  The main disadvantage of `mlet` is that it's evaluation model is strictly
  secuential. It is ok for some use cases, when the sequential order is mandatory.
  
negative.code: = promesa - composable promise library for ClojureScript
  Andrey Antukh, <niwi@niwi.nz>
  0.5.0
  :toc: left
  :!numbered:
  :idseparator: -
  