AIMA code notes - last modified 10/01/03

* The test structures perform  (run-environment (make-x-world...)...),
  where x is wumpus or vacuum. 
* The function run-environment is defined in environments/basic-env. 
* The function make-x-world is implicitely defined when 
  (defstructure (x-world...)...) is evaluated. It is like a constructor. 
* The defstructures are in environments/x.lisp.

* The "program" slot in the agents structure 
  (e.g., (defstructure (random-wumpus-agent...)...) in 
  agents/agents/wumpus.lisp) is a lambda expression (i.e., a nameless 
  function) that just accepts percepts and returns an action. 
* This is defined differently for each agent but is used in the same way by 
  the environments.