Rule DSL

For explicit rulebase composition, define-rulebase creates a named rulebase and extend-rulebase returns a new rulebase with additional clauses, leaving the base object unchanged:

(define-rulebase *base*
  ((color apple red)))

(defparameter *extended*
  (extend-rulebase *base*
    ((color lime green))))

(query-prolog *extended* '(color ?fruit ?color))

In the prolog / def-rule DSL you write guards as expressions — (:when (> ?n 10)) — and the macro compiles them to closures. The engine never evaluates user expressions at runtime.

Available forms

• prolog — build a rulebase from clauses
• define-rulebase — defparameter + prolog
• extend-rulebase — functional extension; the new clauses shadow the base
• def-rule — define a reusable clause-producing form
• with-prolog-query — bind variables from the first solution
• prolog-match — cond over queries

Clause shape: ((pred args...)) is a fact, (head goal...) is a rule.

Foreign predicates

Extend the goal set with define-foreign-predicate. Foreign predicates use the engine’s CPS solution protocol and dispatch by exact name and arity:

(define-foreign-predicate (choose output) (rulebase environment depth emit)
  (declare (ignore rulebase depth))
  (dolist (value '(left right))
    (multiple-value-bind (extended ok) (unify output value environment)
      (when ok (funcall emit extended)))))