prolog: cross-validate compiler vs interpreter (+17)

lib/prolog/compiler.sx

@@ -155,3 +155,22 @@
         (keys src-table))
       (dict-set! db :compiled compiled-table)
       db)))
+
+;; Cross-validate: load src into both a plain and a compiled DB,
+;; run goal-str through each, return true iff solution counts match.
+;; Use this to keep the interpreter as the reference implementation.
+(define
+  pl-compiled-matches-interp?
+  (fn
+    (src goal-str)
+    (let
+      ((db-interp (pl-mk-db)) (db-comp (pl-mk-db)))
+      (pl-db-load! db-interp (pl-parse src))
+      (pl-db-load! db-comp (pl-parse src))
+      (pl-compile-db! db-comp)
+      (let
+        ((gi (pl-instantiate (pl-parse-goal goal-str) {}))
+          (gc (pl-instantiate (pl-parse-goal goal-str) {})))
+        (=
+          (pl-solve-count! db-interp gi (pl-mk-trail))
+          (pl-solve-count! db-comp gc (pl-mk-trail)))))))