;;; -*- Mode: Lisp; Syntax: Common-Lisp; -*- File: logic/fol.lisp

;;;; First Order Logic

(defun tell (kb sentence)
  "Generic TELL function adds a sentence to a knowledge base."
  (etypecase kb
    (prop-kb (prop-tell kb sentence))
    (horn-kb (horn-tell kb sentence))
    (fol-kb  (fol-tell  kb sentence))))

(defun ask (kb sentence)
  "Generic ASK function adds a sentence to a knowledge base."
  (etypecase kb
    (prop-kb (prop-ask kb sentence))
    (horn-kb (horn-ask kb sentence))
    (fol-kb  (fol-ask  kb sentence))))

(defun ask-pattern (kb pattern sentence)
  "Ask if sentence is true; if it is, substitute bindings into variables."
  (subst-bindings (ask kb sentence) (logic pattern)))

(defun retract (kb sentence)
  "Generic RETRACT function adds a sentence to a knowledge base."
  (etypecase kb
    (prop-kb (prop-retract kb sentence))
    (horn-kb (horn-retract kb sentence))
    (fol-kb  (fol-retract  kb sentence))))

;;;;