prolog: clause DB + loader (functor/arity → clauses), 14 tests green

lib/prolog/runtime.sx

@@ -230,3 +230,51 @@
         (pl-unify! t1 t2 trail)
         true
         (do (pl-trail-undo-to! trail mark) false)))))
+
+(define pl-mk-db (fn () {:clauses {}}))
+
+(define
+  pl-head-key
+  (fn
+    (head)
+    (cond
+      ((pl-compound? head) (str (pl-fun head) "/" (len (pl-args head))))
+      ((pl-atom? head) (str (pl-atom-name head) "/0"))
+      (true (error "pl-head-key: invalid head")))))
+
+(define pl-clause-key (fn (clause) (pl-head-key (nth clause 1))))
+
+(define pl-goal-key (fn (goal) (pl-head-key goal)))
+
+(define
+  pl-db-add!
+  (fn
+    (db clause)
+    (let
+      ((key (pl-clause-key clause)) (table (dict-get db :clauses)))
+      (cond
+        ((nil? (dict-get table key)) (dict-set! table key (list clause)))
+        (true (begin (append! (dict-get table key) clause) nil))))))
+
+(define
+  pl-db-load!
+  (fn
+    (db program)
+    (cond
+      ((empty? program) nil)
+      (true
+        (begin
+          (pl-db-add! db (first program))
+          (pl-db-load! db (rest program)))))))
+
+(define
+  pl-db-lookup
+  (fn
+    (db key)
+    (let
+      ((v (dict-get (dict-get db :clauses) key)))
+      (cond ((nil? v) (list)) (true v)))))
+
+(define
+  pl-db-lookup-goal
+  (fn (db goal) (pl-db-lookup db (pl-goal-key goal))))