prolog-query SX API: pl-load + pl-query-all + pl-query-one + pl-query (+16 tests)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/prolog/query.sx

@@ -0,0 +1,114 @@
+;; lib/prolog/query.sx — high-level Prolog query API for SX/Hyperscript callers.
+;;
+;; Requires tokenizer.sx, parser.sx, runtime.sx to be loaded first.
+;;
+;; Public API:
+;;   (pl-load source-str)                → db
+;;   (pl-query-all db query-str)         → list of solution dicts {var-name → term-string}
+;;   (pl-query-one db query-str)         → first solution dict or nil
+;;   (pl-query source-str query-str)     → list of solution dicts (convenience)
+
+;; Collect variable name strings from a parse-time AST (pre-instantiation).
+;; Returns list of unique strings, excluding anonymous "_".
+(define
+  pl-query-extract-vars
+  (fn
+    (ast)
+    (let
+      ((seen {}))
+      (let
+        ((collect!
+          (fn
+            (t)
+            (cond
+              ((not (list? t)) nil)
+              ((empty? t) nil)
+              ((= (first t) "var")
+                (if
+                  (not (= (nth t 1) "_"))
+                  (dict-set! seen (nth t 1) true)
+                  nil))
+              ((= (first t) "compound")
+                (for-each collect! (nth t 2)))
+              (true nil)))))
+        (collect! ast)
+        (keys seen)))))
+
+;; Build a solution dict from a var-env after a successful solve.
+;; Maps each variable name string to its formatted term value.
+(define
+  pl-query-solution-dict
+  (fn
+    (var-names var-env)
+    (let
+      ((d {}))
+      (for-each
+        (fn (name) (dict-set! d name (pl-format-term (dict-get var-env name))))
+        var-names)
+      d)))
+
+;; Parse source-str and load clauses into a fresh DB.
+;; Returns the DB for reuse across multiple queries.
+(define
+  pl-load
+  (fn
+    (source-str)
+    (let
+      ((db (pl-mk-db)))
+      (if
+        (and (string? source-str) (not (= source-str "")))
+        (pl-db-load! db (pl-parse source-str))
+        nil)
+      db)))
+
+;; Run query-str against db, returning a list of solution dicts.
+;; Each dict maps variable name strings to their formatted term values.
+;; Returns an empty list if no solutions.
+(define
+  pl-query-all
+  (fn
+    (db query-str)
+    (let
+      ((parsed (pl-parse (str "q_ :- " query-str "."))))
+      (let
+        ((body-ast (nth (first parsed) 2)))
+        (let
+          ((var-names (pl-query-extract-vars body-ast))
+           (var-env {}))
+          (let
+            ((goal (pl-instantiate body-ast var-env))
+             (trail (pl-mk-trail))
+             (solutions (list)))
+            (let
+              ((mark (pl-trail-mark trail)))
+              (pl-solve!
+                db
+                goal
+                trail
+                {:cut false}
+                (fn
+                  ()
+                  (begin
+                    (append!
+                      solutions
+                      (pl-query-solution-dict var-names var-env))
+                    false)))
+              (pl-trail-undo-to! trail mark)
+              solutions)))))))
+
+;; Return the first solution dict, or nil if no solutions.
+(define
+  pl-query-one
+  (fn
+    (db query-str)
+    (let
+      ((all (pl-query-all db query-str)))
+      (if (empty? all) nil (first all)))))
+
+;; Convenience: parse source-str, then run query-str against it.
+;; Returns a list of solution dicts. Creates a fresh DB each call.
+(define
+  pl-query
+  (fn
+    (source-str query-str)
+    (pl-query-all (pl-load source-str) query-str)))