title: Is it an idea of OOP?
body: <p>I have learned data-directed programming from the chapter 2.4 of the SICP, and then I continued to study the chapter 2.5. When I saw the "Tower of types" and "inherit", an thought flashed, is it an idea of OOP? Each package is an object and the "tower of types" shows the relation among the types which has the same meaning like "inherit" in OOP.</p>
  
  <p>I am so excited and hope to know the answer!</p>