datalog: db + naive eval + safety analysis (Phase 3, 87/87)

db.sx: facts indexed by relation name, rules list, dl-add-fact!
(rejects non-ground), dl-add-rule! (rejects unsafe — head vars
not in positive body). eval.sx: dl-saturate! fixpoint, dl-query
with deduped projected results. Negation and arithmetic raise
clear errors (Phase 4/7 to follow). 15 eval tests: transitive
closure, sibling, same-gen, grandparent, cyclic reach, safety.

lib/datalog/tests/eval.sx

@@ -0,0 +1,206 @@
+;; lib/datalog/tests/eval.sx — naive evaluation + safety analysis tests.
+
+(define dl-et-pass 0)
+(define dl-et-fail 0)
+(define dl-et-failures (list))
+
+;; Same deep-equal helper used in other suites.
+(define
+  dl-et-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-et-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let
+          ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-et-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-et-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-et-deep=? (nth a i) (nth b i))) false)
+      (else (dl-et-deq-l? a b (+ i 1))))))
+
+(define
+  dl-et-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i))) (not (dl-et-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-et-deq-d? a b ka (+ i 1))))))
+
+;; Set-equality on lists (order-independent, uses dl-et-deep=?).
+(define
+  dl-et-set=?
+  (fn
+    (a b)
+    (and (= (len a) (len b)) (dl-et-subset? a b) (dl-et-subset? b a))))
+
+(define
+  dl-et-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-et-contains? ys (first xs))) false)
+      (else (dl-et-subset? (rest xs) ys)))))
+
+(define
+  dl-et-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-et-deep=? (first xs) target) true)
+      (else (dl-et-contains? (rest xs) target)))))
+
+(define
+  dl-et-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-et-deep=? got expected)
+      (set! dl-et-pass (+ dl-et-pass 1))
+      (do
+        (set! dl-et-fail (+ dl-et-fail 1))
+        (append!
+          dl-et-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define
+  dl-et-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-et-set=? got expected)
+      (set! dl-et-pass (+ dl-et-pass 1))
+      (do
+        (set! dl-et-fail (+ dl-et-fail 1))
+        (append!
+          dl-et-failures
+          (str
+            name
+            "\n    expected (set): "
+            expected
+            "\n    got:            "
+            got))))))
+
+(define
+  dl-et-throws?
+  (fn
+    (thunk)
+    (let
+      ((threw false))
+      (do (guard (e (#t (set! threw true))) (thunk)) threw))))
+
+(define
+  dl-et-run-all!
+  (fn
+    ()
+    (do
+      (dl-et-test-set!
+        "fact lookup any"
+        (dl-query
+          (dl-program "parent(tom, bob). parent(bob, ann).")
+          (list (quote parent) (quote X) (quote Y)))
+        (list {:X (quote tom) :Y (quote bob)} {:X (quote bob) :Y (quote ann)}))
+      (dl-et-test-set!
+        "fact lookup constant arg"
+        (dl-query
+          (dl-program "parent(tom, bob). parent(tom, liz). parent(bob, ann).")
+          (list (quote parent) (quote tom) (quote Y)))
+        (list {:Y (quote bob)} {:Y (quote liz)}))
+      (dl-et-test-set!
+        "no match"
+        (dl-query
+          (dl-program "parent(tom, bob).")
+          (list (quote parent) (quote nobody) (quote X)))
+        (list))
+      (dl-et-test-set!
+        "ancestor closure"
+        (dl-query
+          (dl-program
+            "parent(tom, bob). parent(bob, ann). parent(ann, pat).\n             ancestor(X, Y) :- parent(X, Y).\n             ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")
+          (list (quote ancestor) (quote tom) (quote X)))
+        (list {:X (quote bob)} {:X (quote ann)} {:X (quote pat)}))
+      (dl-et-test-set!
+        "sibling"
+        (dl-query
+          (dl-program
+            "parent(tom, bob). parent(tom, liz). parent(jane, bob). parent(jane, liz).\n             sibling(X, Y) :- parent(P, X), parent(P, Y).")
+          (list (quote sibling) (quote bob) (quote Y)))
+        (list {:Y (quote bob)} {:Y (quote liz)}))
+      (dl-et-test-set!
+        "same-generation"
+        (dl-query
+          (dl-program
+            "parent(tom, bob). parent(tom, liz). parent(bob, ann). parent(liz, joe).\n             person(tom). person(bob). person(liz). person(ann). person(joe).\n             sg(X, X) :- person(X).\n             sg(X, Y) :- parent(P1, X), sg(P1, P2), parent(P2, Y).")
+          (list (quote sg) (quote ann) (quote X)))
+        (list {:X (quote ann)} {:X (quote joe)}))
+      (dl-et-test!
+        "ancestor count"
+        (let
+          ((db (dl-program "parent(a, b). parent(b, c). parent(c, d).\n                  ancestor(X, Y) :- parent(X, Y).\n                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (do (dl-saturate! db) (len (dl-relation db "ancestor"))))
+        6)
+      (dl-et-test-set!
+        "grandparent"
+        (dl-query
+          (dl-program
+            "parent(a, b). parent(b, c). parent(c, d).\n             grandparent(X, Z) :- parent(X, Y), parent(Y, Z).")
+          (list (quote grandparent) (quote X) (quote Y)))
+        (list {:X (quote a) :Y (quote c)} {:X (quote b) :Y (quote d)}))
+      (dl-et-test!
+        "no recursion infinite loop"
+        (let
+          ((db (dl-program "edge(1, 2). edge(2, 3). edge(3, 1).\n                  reach(X, Y) :- edge(X, Y).\n                  reach(X, Z) :- edge(X, Y), reach(Y, Z).")))
+          (do (dl-saturate! db) (len (dl-relation db "reach"))))
+        9)
+      (dl-et-test!
+        "unsafe head var"
+        (dl-et-throws? (fn () (dl-program "p(X, Y) :- q(X).")))
+        true)
+      (dl-et-test!
+        "unsafe — empty body"
+        (dl-et-throws? (fn () (dl-program "p(X) :- .")))
+        true)
+      (dl-et-test!
+        "underscore var ok"
+        (dl-et-throws? (fn () (dl-program "p(X, _) :- q(X).")))
+        false)
+      (dl-et-test!
+        "var only in head — unsafe"
+        (dl-et-throws? (fn () (dl-program "p(X, Y) :- q(Z).")))
+        true)
+      (dl-et-test!
+        "head var bound by body"
+        (dl-et-throws? (fn () (dl-program "p(X) :- q(X).")))
+        false)
+      (dl-et-test!
+        "head subset of body"
+        (dl-et-throws?
+          (fn
+            ()
+            (dl-program
+              "edge(a,b). edge(b,c). reach(X, Z) :- edge(X, Y), edge(Y, Z).")))
+        false))))
+
+(define
+  dl-eval-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-et-pass 0)
+      (set! dl-et-fail 0)
+      (set! dl-et-failures (list))
+      (dl-et-run-all!)
+      {:failures dl-et-failures :total (+ dl-et-pass dl-et-fail) :passed dl-et-pass :failed dl-et-fail})))