anchor.diff:  
   The difference of indexed and associative compositions is the input and output. In
   associative composition the expected input and output is a map. And in indexed
  -composition, the expected input and input is a vector. Internally them represents
  +composition, the expected input and input is a vector. Internally it represents
   the same value in bytes.
   
   Let start defining one:
  
positive.code:   (reify
      spec/ISpecSize
      (size [_]
        ;; we kwno that is datatype has fixed size in bytes
        ;; that represents two int32.
        8)
  
  
negative.code: == Getting started
  
  The main goal of _octet_ is provide, multiplatform abstraction for work with
  byte buffers. Offering a lightweight api for define message types in a declarative
  way and use them for read or write to bytebuffers.
  
  As previously said, _octet_  works with both most used clojure implementations:
  