prolog: compile clauses to SX closures (+17)

lib/prolog/compiler.sx

@@ -0,0 +1,157 @@
+;; lib/prolog/compiler.sx — clause compiler: parse-AST clauses → SX closures
+;;
+;; Each compiled clause is a lambda (fn (goal trail db cut-box k) bool)
+;; that creates fresh vars, builds the instantiated head/body, and calls
+;; pl-unify! + pl-solve! directly — no AST walk at solve time.
+;;
+;; Usage:
+;;   (pl-db-load! db (pl-parse src))
+;;   (pl-compile-db! db)
+;;   ; pl-solve-user! in runtime.sx automatically prefers compiled clauses
+;;   (pl-solve-once! db goal trail)
+
+;; Collect unique variable names from a parse-AST clause into a dict.
+(define
+  pl-cmp-vars-into!
+  (fn
+    (ast seen)
+    (cond
+      ((not (list? ast)) nil)
+      ((empty? ast) nil)
+      ((= (first ast) "var")
+        (let
+          ((name (nth ast 1)))
+          (when
+            (and (not (= name "_")) (not (dict-has? seen name)))
+            (dict-set! seen name true))))
+      ((= (first ast) "compound")
+        (for-each (fn (a) (pl-cmp-vars-into! a seen)) (nth ast 2)))
+      ((= (first ast) "clause")
+        (begin
+          (pl-cmp-vars-into! (nth ast 1) seen)
+          (pl-cmp-vars-into! (nth ast 2) seen))))))
+
+;; Return list of unique var names in a clause (head + body, excluding _).
+(define
+  pl-cmp-collect-vars
+  (fn
+    (clause)
+    (let ((seen {})) (pl-cmp-vars-into! clause seen) (keys seen))))
+
+;; Create a fresh runtime var for each name in the list; return name->var dict.
+(define
+  pl-cmp-make-var-map
+  (fn
+    (var-names)
+    (let
+      ((m {}))
+      (for-each
+        (fn (name) (dict-set! m name (pl-mk-rt-var name)))
+        var-names)
+      m)))
+
+;; Instantiate a parse-AST term using a pre-built var-map.
+;; ("var" "_") always gets a fresh anonymous var.
+(define
+  pl-cmp-build-term
+  (fn
+    (ast var-map)
+    (cond
+      ((pl-var? ast) ast)
+      ((not (list? ast)) ast)
+      ((empty? ast) ast)
+      ((= (first ast) "var")
+        (let
+          ((name (nth ast 1)))
+          (if (= name "_") (pl-mk-rt-var "_") (dict-get var-map name))))
+      ((or (= (first ast) "atom") (= (first ast) "num") (= (first ast) "str"))
+        ast)
+      ((= (first ast) "compound")
+        (list
+          "compound"
+          (nth ast 1)
+          (map (fn (a) (pl-cmp-build-term a var-map)) (nth ast 2))))
+      ((= (first ast) "clause")
+        (list
+          "clause"
+          (pl-cmp-build-term (nth ast 1) var-map)
+          (pl-cmp-build-term (nth ast 2) var-map)))
+      (true ast))))
+
+;; Compile one parse-AST clause to a lambda.
+;; Pre-computes var names at compile time; creates fresh vars per call.
+(define
+  pl-compile-clause
+  (fn
+    (clause)
+    (let
+      ((var-names (pl-cmp-collect-vars clause))
+        (head-ast (nth clause 1))
+        (body-ast (nth clause 2)))
+      (fn
+        (goal trail db cut-box k)
+        (let
+          ((var-map (pl-cmp-make-var-map var-names)))
+          (let
+            ((fresh-head (pl-cmp-build-term head-ast var-map))
+              (fresh-body (pl-cmp-build-term body-ast var-map)))
+            (let
+              ((mark (pl-trail-mark trail)))
+              (if
+                (pl-unify! goal fresh-head trail)
+                (let
+                  ((r (pl-solve! db fresh-body trail cut-box k)))
+                  (if r true (begin (pl-trail-undo-to! trail mark) false)))
+                (begin (pl-trail-undo-to! trail mark) false)))))))))
+
+;; Try a list of compiled clause lambdas — same cut semantics as pl-try-clauses!.
+(define
+  pl-try-compiled-clauses!
+  (fn
+    (db
+      goal
+      trail
+      compiled-clauses
+      outer-cut-box
+      outer-was-cut
+      inner-cut-box
+      k)
+    (cond
+      ((empty? compiled-clauses) false)
+      (true
+        (let
+          ((r ((first compiled-clauses) goal trail db inner-cut-box k)))
+          (cond
+            (r true)
+            ((dict-get inner-cut-box :cut) false)
+            ((and (not outer-was-cut) (dict-get outer-cut-box :cut)) false)
+            (true
+              (pl-try-compiled-clauses!
+                db
+                goal
+                trail
+                (rest compiled-clauses)
+                outer-cut-box
+                outer-was-cut
+                inner-cut-box
+                k))))))))
+
+;; Compile all clauses in DB and store in :compiled table.
+;; After this call, pl-solve-user! will dispatch via compiled lambdas.
+;; Note: clauses assert!-ed after this call are not compiled.
+(define
+  pl-compile-db!
+  (fn
+    (db)
+    (let
+      ((src-table (dict-get db :clauses)) (compiled-table {}))
+      (for-each
+        (fn
+          (key)
+          (dict-set!
+            compiled-table
+            key
+            (map pl-compile-clause (dict-get src-table key))))
+        (keys src-table))
+      (dict-set! db :compiled compiled-table)
+      db)))