;;; THE INTRO TO AI SHOW
;;; Summer Session I 1999
;;; 
;;; DEMO:
;;; A simple reflex agent from Figure 2.8 in AIMA text
;;;
;;; Note:  This demo makes indiscriminate use of special
;;; variables.  It is intended to be a quick and dirty
;;; instantiation of a simple reflex agent.  What assumptions are made
;;; about Willard's environment given the use of special variables
;;; herein?
;;;
;;; Selmer Bringsjord

;;; The initial state.
(defvar *state* 'hailing)

;;; The set of invariant condition-action rules.
(defvar *rules* '((raining get-umbrella)
              (snowing get-dynastars)
              (sunning get-burner-bubble)
              (freezing get-prince-raquet)
              (hailing get-inside)))

;;; The mapping from scene snapshots to states.
(defvar *percept->state* '((snapshot1 raining)
              (snapshot2 snowing)
              (snapshot3 freezing)
              (snapshot4 sunning)
              (snapshot5 hailing)))

(defun willard (p)
  "The agent Willard.  Percept in, action back."
  (setf *state* (interpret-input p))
  (rule-match *state*))

(defun rule-match (state)
  "Takes a weather state and returns an appropriate action."
  (let ((result-rule nil))
    (dolist (rule *rules* result-rule)
      (when (eql state (first rule))
        (setf result-rule (second rule))))))

(defun interpret-input (snapshot)
  "Takes a snapshot, a visual scene, and returns a metereological condition."
  (let ((result-rule nil))
    (dolist (rule *percept->state* result-rule)
      (when (eql snapshot (first rule))
        (setf result-rule (second rule))))))