datalog: magic pre-saturation is conditional, not unconditional

Previously dl-magic-query always pre-saturated the source db so it
gave correct results for stratified programs (where the rewriter
doesn't propagate magic to aggregate inner-goals or negated rels).
Pure positive programs paid the full bottom-up cost twice.

Add dl-rules-need-presaturation? — checks whether any rule body
contains an aggregate or negation. Only pre-saturate in that case.
Pure positive programs (the common case for magic-sets) keep their
full goal-directed efficiency.

276/276; identical answers on the existing aggregate-of-IDB test.

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

lib/datalog/aggregates.sx

@@ -0,0 +1,157 @@
+;; lib/datalog/aggregates.sx — count / sum / min / max / findall.
+;;
+;; Surface form (always 3-arg after the relation name):
+;;
+;;   (count   Result  Var  GoalLit)
+;;   (sum     Result  Var  GoalLit)
+;;   (min     Result  Var  GoalLit)
+;;   (max     Result  Var  GoalLit)
+;;   (findall List    Var  GoalLit)
+;;
+;; Parsed naturally because arg-position compounds are already allowed
+;; (Phase 4 needs them for arithmetic). At evaluation time the aggregator
+;; runs `dl-find-bindings` on `GoalLit` under the current subst, collects
+;; the distinct values of `Var`, and binds `Result`.
+;;
+;; Aggregation is non-monotonic — `count(C, X, p(X))` shrinks as p loses
+;; tuples. The stratifier (lib/datalog/strata.sx) treats every aggregate's
+;; goal relation as a negation-like edge so the inner relation is fully
+;; derived before the aggregate fires.
+;;
+;; Empty input: count → 0, sum → 0, min/max → no binding (rule fails).
+
+(define dl-aggregate-rels (list "count" "sum" "min" "max" "findall"))
+
+(define
+  dl-aggregate?
+  (fn
+    (lit)
+    (and
+      (list? lit)
+      (>= (len lit) 4)
+      (let ((rel (dl-rel-name lit)))
+        (cond
+          ((nil? rel) false)
+          (else (dl-member-string? rel dl-aggregate-rels)))))))
+
+;; Apply aggregation operator to a list of (already-distinct) numeric or
+;; symbolic values. Returns the aggregated value, or :empty if min/max
+;; has no input.
+(define
+  dl-do-aggregate
+  (fn
+    (op vals)
+    (cond
+      ((= op "count") (len vals))
+      ((= op "sum") (dl-sum-vals vals 0))
+      ((= op "findall") vals)
+      ((= op "min")
+        (cond
+          ((= (len vals) 0) :empty)
+          (else (dl-min-vals vals 1 (first vals)))))
+      ((= op "max")
+        (cond
+          ((= (len vals) 0) :empty)
+          (else (dl-max-vals vals 1 (first vals)))))
+      (else (error (str "datalog: unknown aggregate " op))))))
+
+(define
+  dl-sum-vals
+  (fn
+    (vals acc)
+    (cond
+      ((= (len vals) 0) acc)
+      (else (dl-sum-vals (rest vals) (+ acc (first vals)))))))
+
+(define
+  dl-min-vals
+  (fn
+    (vals i cur)
+    (cond
+      ((>= i (len vals)) cur)
+      (else
+        (let ((v (nth vals i)))
+          (dl-min-vals vals (+ i 1) (if (< v cur) v cur)))))))
+
+(define
+  dl-max-vals
+  (fn
+    (vals i cur)
+    (cond
+      ((>= i (len vals)) cur)
+      (else
+        (let ((v (nth vals i)))
+          (dl-max-vals vals (+ i 1) (if (> v cur) v cur)))))))
+
+;; Membership check by deep equality (so 30 == 30.0 etc).
+(define
+  dl-val-member?
+  (fn
+    (v xs)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-tuple-equal? v (first xs)) true)
+      (else (dl-val-member? v (rest xs))))))
+
+;; Evaluate an aggregate body lit under `subst`. Returns the list of
+;; extended substitutions (0 or 1 element).
+(define
+  dl-eval-aggregate
+  (fn
+    (lit db subst)
+    (let
+      ((op (dl-rel-name lit))
+        (result-var (nth lit 1))
+        (agg-var (nth lit 2))
+        (goal (nth lit 3)))
+      (cond
+        ((not (dl-var? agg-var))
+          (error (str "datalog aggregate (" op
+                      "): second arg must be a variable, got " agg-var)))
+        ((not (and (list? goal) (> (len goal) 0)
+                   (symbol? (first goal))))
+          (error (str "datalog aggregate (" op
+                      "): third arg must be a positive literal, got "
+                      goal)))
+        ((not (dl-member-string?
+                (symbol->string agg-var)
+                (dl-vars-of goal)))
+          (error (str "datalog aggregate (" op
+                      "): aggregation variable " agg-var
+                      " does not appear in the goal " goal
+                      " — without it every match contributes the same "
+                      "(unbound) value and the result is meaningless")))
+        (else
+          (let ((vals (list)))
+            (do
+              (for-each
+                (fn
+                  (s)
+                  (let ((v (dl-apply-subst agg-var s)))
+                    (when (not (dl-val-member? v vals))
+                      (append! vals v))))
+                (dl-find-bindings (list goal) db subst))
+              (let ((agg-val (dl-do-aggregate op vals)))
+                (cond
+                  ((= agg-val :empty) (list))
+                  (else
+                    (let ((s2 (dl-unify result-var agg-val subst)))
+                      (if (nil? s2) (list) (list s2)))))))))))))
+
+
+;; Stratification edges from aggregates: like negation, the goal's
+;; relation must be in a strictly lower stratum so that the aggregate
+;; fires only after the underlying tuples are settled.
+(define
+  dl-aggregate-dep-edge
+  (fn
+    (lit)
+    (cond
+      ((dl-aggregate? lit)
+        (let ((goal (nth lit 3)))
+          (cond
+            ((and (list? goal) (> (len goal) 0))
+              (let ((rel (dl-rel-name goal)))
+                (if (nil? rel) nil {:rel rel :neg true})))
+            (else nil))))
+      (else nil))))

lib/datalog/api.sx

@@ -0,0 +1,303 @@
+;; lib/datalog/api.sx — SX-data embedding API.
+;;
+;; Where Phase 1's `dl-program` takes a Datalog source string,
+;; this module exposes a parser-free API that consumes SX data
+;; directly. Two rule shapes are accepted:
+;;
+;;   - dict:   {:head <literal> :body (<literal> ...)}
+;;   - list:   (<head-elements...> <- <body-literal> ...)
+;;             — `<-` is an SX symbol used as the rule arrow.
+;;
+;; Examples:
+;;
+;;   (dl-program-data
+;;     '((parent tom bob) (parent tom liz) (parent bob ann))
+;;     '((ancestor X Y <- (parent X Y))
+;;       (ancestor X Z <- (parent X Y) (ancestor Y Z))))
+;;
+;;   (dl-query db '(ancestor tom X))   ; same query API as before
+;;
+;; Variables follow the parser convention: SX symbols whose first
+;; character is uppercase or `_` are variables.
+
+(define
+  dl-rule
+  (fn (head body) {:head head :body body}))
+
+(define
+  dl-rule-arrow?
+  (fn
+    (x)
+    (and (symbol? x) (= (symbol->string x) "<-"))))
+
+(define
+  dl-find-arrow
+  (fn
+    (rl i n)
+    (cond
+      ((>= i n) nil)
+      ((dl-rule-arrow? (nth rl i)) i)
+      (else (dl-find-arrow rl (+ i 1) n)))))
+
+;; Given a list of the form (head-elt ... <- body-lit ...) returns
+;; {:head (head-elt ...) :body (body-lit ...)}. If no arrow is
+;; present, the whole list is treated as the head and the body is
+;; empty (i.e. a fact written rule-style).
+(define
+  dl-rule-from-list
+  (fn
+    (rl)
+    (let ((n (len rl)))
+      (let ((idx (dl-find-arrow rl 0 n)))
+        (cond
+          ((nil? idx) {:head rl :body (list)})
+          (else
+            (let
+              ((head (slice rl 0 idx))
+                (body (slice rl (+ idx 1) n)))
+              {:head head :body body})))))))
+
+;; Coerce a rule given as either a dict or a list-with-arrow to a dict.
+(define
+  dl-coerce-rule
+  (fn
+    (r)
+    (cond
+      ((dict? r) r)
+      ((list? r) (dl-rule-from-list r))
+      (else (error (str "dl-coerce-rule: expected dict or list, got " r))))))
+
+;; Build a db from SX data lists.
+(define
+  dl-program-data
+  (fn
+    (facts rules)
+    (let ((db (dl-make-db)))
+      (do
+        (for-each (fn (lit) (dl-add-fact! db lit)) facts)
+        (for-each
+          (fn (r) (dl-add-rule! db (dl-coerce-rule r)))
+          rules)
+        db))))
+
+;; Add a single fact at runtime, then re-saturate the db so derived
+;; tuples reflect the change. Returns the db.
+(define
+  dl-assert!
+  (fn
+    (db lit)
+    (do
+      (dl-add-fact! db lit)
+      (dl-saturate! db)
+      db)))
+
+;; Remove a fact and re-saturate. Mixed relations (which have BOTH
+;; user-asserted facts AND rules) are supported via :edb-keys provenance
+;; — explicit facts are marked at dl-add-fact! time, the saturator uses
+;; dl-add-derived! which doesn't mark them, so the retract pass can
+;; safely wipe IDB-derived tuples while preserving the user's EDB.
+;;
+;; Effect:
+;;   - remove tuples matching `lit` from :facts and :edb-keys
+;;   - for every relation that has a rule (i.e. potentially IDB or
+;;     mixed), drop the IDB-derived portion (anything not in :edb-keys)
+;;     so the saturator can re-derive cleanly
+;;   - re-saturate
+(define
+  dl-retract!
+  (fn
+    (db lit)
+    (let
+      ((rel-key (dl-rel-name lit)))
+      (do
+        ;; Drop the matching tuple from its relation list, its facts-keys,
+        ;; its first-arg index, AND from :edb-keys (if present).
+        (when
+          (has-key? (get db :facts) rel-key)
+          (let
+            ((existing (get (get db :facts) rel-key))
+              (kept (list))
+              (kept-keys {})
+              (kept-index {})
+              (edb-rel (cond
+                         ((has-key? (get db :edb-keys) rel-key)
+                           (get (get db :edb-keys) rel-key))
+                         (else nil)))
+              (kept-edb {}))
+            (do
+              (for-each
+                (fn
+                  (t)
+                  (when
+                    (not (dl-tuple-equal? t lit))
+                    (do
+                      (append! kept t)
+                      (let ((tk (dl-tuple-key t)))
+                        (do
+                          (dict-set! kept-keys tk true)
+                          (when
+                            (and (not (nil? edb-rel))
+                                 (has-key? edb-rel tk))
+                            (dict-set! kept-edb tk true))))
+                      (when
+                        (>= (len t) 2)
+                        (let ((k (dl-arg-key (nth t 1))))
+                          (do
+                            (when
+                              (not (has-key? kept-index k))
+                              (dict-set! kept-index k (list)))
+                            (append! (get kept-index k) t)))))))
+                existing)
+              (dict-set! (get db :facts) rel-key kept)
+              (dict-set! (get db :facts-keys) rel-key kept-keys)
+              (dict-set! (get db :facts-index) rel-key kept-index)
+              (when
+                (not (nil? edb-rel))
+                (dict-set! (get db :edb-keys) rel-key kept-edb)))))
+        ;; For each rule-head relation, strip the IDB-derived tuples
+        ;; (anything not marked in :edb-keys) so the saturator can
+        ;; cleanly re-derive without leaving stale tuples that depended
+        ;; on the now-removed fact.
+        (let ((rule-heads (dl-rule-head-rels db)))
+          (for-each
+            (fn
+              (k)
+              (when
+                (has-key? (get db :facts) k)
+                (let
+                  ((existing (get (get db :facts) k))
+                    (kept (list))
+                    (kept-keys {})
+                    (kept-index {})
+                    (edb-rel (cond
+                               ((has-key? (get db :edb-keys) k)
+                                 (get (get db :edb-keys) k))
+                               (else {}))))
+                  (do
+                    (for-each
+                      (fn
+                        (t)
+                        (let ((tk (dl-tuple-key t)))
+                          (when
+                            (has-key? edb-rel tk)
+                            (do
+                              (append! kept t)
+                              (dict-set! kept-keys tk true)
+                              (when
+                                (>= (len t) 2)
+                                (let ((kk (dl-arg-key (nth t 1))))
+                                  (do
+                                    (when
+                                      (not (has-key? kept-index kk))
+                                      (dict-set! kept-index kk (list)))
+                                    (append! (get kept-index kk) t))))))))
+                      existing)
+                    (dict-set! (get db :facts) k kept)
+                    (dict-set! (get db :facts-keys) k kept-keys)
+                    (dict-set! (get db :facts-index) k kept-index)))))
+            rule-heads))
+        (dl-saturate! db)
+        db))))
+
+;; ── Convenience: single-call source + query ───────────────────
+;; (dl-eval source query-source) parses both, builds a db, saturates,
+;; runs the query, returns the substitution list. The query source
+;; should be `?- goal[, goal ...].` — the parser produces a clause
+;; with :query containing a list of literals which is fed straight
+;; to dl-query.
+(define
+  dl-eval
+  (fn
+    (source query-source)
+    (let
+      ((db (dl-program source))
+        (queries (dl-parse query-source)))
+      (cond
+        ((= (len queries) 0) (error "dl-eval: query string is empty"))
+        ((not (has-key? (first queries) :query))
+          (error "dl-eval: second arg must be a `?- ...` query clause"))
+        (else
+          (dl-query db (get (first queries) :query)))))))
+
+;; (dl-eval-magic source query-source) — like dl-eval but routes a
+;; single-positive-literal query through `dl-magic-query` for goal-
+;; directed evaluation. Multi-literal query bodies fall back to the
+;; standard dl-query path (magic-sets is currently only wired for
+;; single-positive goals). The caller's source is parsed afresh
+;; each call so successive invocations are independent.
+(define
+  dl-eval-magic
+  (fn
+    (source query-source)
+    (let
+      ((db (dl-program source))
+        (queries (dl-parse query-source)))
+      (cond
+        ((= (len queries) 0) (error "dl-eval-magic: query string is empty"))
+        ((not (has-key? (first queries) :query))
+          (error
+            "dl-eval-magic: second arg must be a `?- ...` query clause"))
+        (else
+          (let
+            ((qbody (get (first queries) :query)))
+            (cond
+              ((and (= (len qbody) 1)
+                    (list? (first qbody))
+                    (> (len (first qbody)) 0)
+                    (symbol? (first (first qbody))))
+                (dl-magic-query db (first qbody)))
+              (else (dl-query db qbody)))))))))
+
+;; List rules whose head's relation matches `rel-name`. Useful for
+;; inspection ("show me how this relation is derived") without
+;; exposing the internal `:rules` list.
+(define
+  dl-rules-of
+  (fn
+    (db rel-name)
+    (let ((out (list)))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (when
+              (= (dl-rel-name (get rule :head)) rel-name)
+              (append! out rule)))
+          (dl-rules db))
+        out))))
+
+(define
+  dl-rule-head-rels
+  (fn
+    (db)
+    (let ((seen (list)))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (let ((h (dl-rel-name (get rule :head))))
+              (when
+                (and (not (nil? h)) (not (dl-member-string? h seen)))
+                (append! seen h))))
+          (dl-rules db))
+        seen))))
+
+;; Wipe every relation that has at least one rule (i.e. every IDB
+;; relation) — leaves EDB facts and rule definitions intact. Useful
+;; before a follow-up `dl-saturate!` if you want a clean restart, or
+;; for inspection of the EDB-only baseline.
+(define
+  dl-clear-idb!
+  (fn
+    (db)
+    (let ((rule-heads (dl-rule-head-rels db)))
+      (do
+        (for-each
+          (fn
+            (k)
+            (do
+              (dict-set! (get db :facts) k (list))
+              (dict-set! (get db :facts-keys) k {})
+              (dict-set! (get db :facts-index) k {})))
+          rule-heads)
+        db))))

lib/datalog/builtins.sx

@@ -0,0 +1,406 @@
+;; lib/datalog/builtins.sx — comparison + arithmetic body literals.
+;;
+;; Built-in predicates filter / extend candidate substitutions during
+;; rule evaluation. They are not stored facts and do not participate in
+;; the Herbrand base.
+;;
+;;   (< a b)  (<= a b)  (> a b)  (>= a b)   ; numeric (or string) compare
+;;   (= a b)                                  ; unify (binds vars)
+;;   (!= a b)                                ; ground-only inequality
+;;   (is X expr)                              ; bind X to expr's value
+;;
+;; Arithmetic expressions are SX-list compounds:
+;;   (+ a b)  (- a b)  (* a b)  (/ a b)
+;; or numbers / variables (must be bound at evaluation time).
+
+(define
+  dl-comparison?
+  (fn
+    (lit)
+    (and
+      (list? lit)
+      (> (len lit) 0)
+      (let
+        ((rel (dl-rel-name lit)))
+        (cond
+          ((nil? rel) false)
+          (else (dl-member-string? rel (list "<" "<=" ">" ">=" "!="))))))))
+
+(define
+  dl-eq?
+  (fn
+    (lit)
+    (and
+      (list? lit)
+      (> (len lit) 0)
+      (let ((rel (dl-rel-name lit))) (and (not (nil? rel)) (= rel "=")))))) 
+
+(define
+  dl-is?
+  (fn
+    (lit)
+    (and
+      (list? lit)
+      (> (len lit) 0)
+      (let
+        ((rel (dl-rel-name lit)))
+        (and (not (nil? rel)) (= rel "is")))))) 
+
+;; Evaluate an arithmetic expression under subst. Returns the numeric
+;; result, or raises if any operand is unbound or non-numeric.
+(define
+  dl-eval-arith
+  (fn
+    (expr subst)
+    (let
+      ((w (dl-walk expr subst)))
+      (cond
+        ((number? w) w)
+        ((dl-var? w)
+          (error (str "datalog arith: unbound variable " (symbol->string w))))
+        ((list? w)
+          (let
+            ((rel (dl-rel-name w)) (args (rest w)))
+            (cond
+              ((not (= (len args) 2))
+                (error (str "datalog arith: need 2 args, got " w)))
+              (else
+                (let
+                  ((a (dl-eval-arith (first args) subst))
+                    (b (dl-eval-arith (nth args 1) subst)))
+                  (cond
+                    ((= rel "+") (+ a b))
+                    ((= rel "-") (- a b))
+                    ((= rel "*") (* a b))
+                    ((= rel "/")
+                      (cond
+                        ((= b 0)
+                          (error
+                            (str "datalog arith: division by zero in "
+                                 w)))
+                        (else (/ a b))))
+                    (else (error (str "datalog arith: unknown op " rel)))))))))
+        (else (error (str "datalog arith: not a number — " w)))))))
+
+;; Comparable types — both operands must be the same primitive type
+;; (both numbers, both strings). `!=` is the exception: it's defined
+;; for any pair (returns true iff not equal) since dl-tuple-equal?
+;; handles type-mixed comparisons.
+(define
+  dl-compare-typeok?
+  (fn
+    (rel a b)
+    (cond
+      ((= rel "!=") true)
+      ((and (number? a) (number? b)) true)
+      ((and (string? a) (string? b)) true)
+      (else false))))
+
+(define
+  dl-eval-compare
+  (fn
+    (lit subst)
+    (let
+      ((rel (dl-rel-name lit))
+        (a (dl-walk (nth lit 1) subst))
+        (b (dl-walk (nth lit 2) subst)))
+      (cond
+        ((or (dl-var? a) (dl-var? b))
+          (error
+            (str
+              "datalog: comparison "
+              rel
+              " has unbound argument; "
+              "ensure prior body literal binds the variable")))
+        ((not (dl-compare-typeok? rel a b))
+          (error
+            (str "datalog: comparison " rel " requires same-type "
+                 "operands (both numbers or both strings), got "
+                 a " and " b)))
+        (else
+          (let
+            ((ok (cond ((= rel "<") (< a b)) ((= rel "<=") (<= a b)) ((= rel ">") (> a b)) ((= rel ">=") (>= a b)) ((= rel "!=") (not (dl-tuple-equal? a b))) (else (error (str "datalog: unknown compare " rel))))))
+            (if ok subst nil)))))))
+
+(define
+  dl-eval-eq
+  (fn
+    (lit subst)
+    (dl-unify (nth lit 1) (nth lit 2) subst)))
+
+(define
+  dl-eval-is
+  (fn
+    (lit subst)
+    (let
+      ((target (nth lit 1)) (expr (nth lit 2)))
+      (let
+        ((value (dl-eval-arith expr subst)))
+        (dl-unify target value subst)))))
+
+(define
+  dl-eval-builtin
+  (fn
+    (lit subst)
+    (cond
+      ((dl-comparison? lit) (dl-eval-compare lit subst))
+      ((dl-eq? lit) (dl-eval-eq lit subst))
+      ((dl-is? lit) (dl-eval-is lit subst))
+      (else (error (str "dl-eval-builtin: not a built-in: " lit))))))
+
+;; ── Safety analysis ──────────────────────────────────────────────
+;;
+;; Walks body literals left-to-right tracking a "bound" set. The check
+;; understands these literal kinds:
+;;
+;;   positive non-built-in    → adds its vars to bound
+;;   (is X expr)              → vars(expr) ⊆ bound, then add X (if var)
+;;   <,<=,>,>=,!=             → all vars ⊆ bound (no binding)
+;;   (= a b) where:
+;;       both non-vars        → constraint check, no binding
+;;       a var, b not         → bind a
+;;       b var, a not         → bind b
+;;       both vars            → at least one in bound; bind the other
+;;   {:neg lit}               → all vars ⊆ bound (Phase 7 enforces fully)
+;;
+;; At end, head vars (minus `_`) must be ⊆ bound.
+
+(define
+  dl-vars-not-in
+  (fn
+    (vs bound)
+    (let
+      ((out (list)))
+      (do
+        (for-each
+          (fn
+            (v)
+            (when (not (dl-member-string? v bound)) (append! out v)))
+          vs)
+        out))))
+
+;; Filter a list of variable-name strings to exclude anonymous-renamed
+;; vars (`_` in source → `_anon*` by dl-rename-anon-term). Used by
+;; the negation safety check, where anonymous vars are existential
+;; within the negated literal.
+(define
+  dl-non-anon-vars
+  (fn
+    (vs)
+    (let
+      ((out (list)))
+      (do
+        (for-each
+          (fn
+            (v)
+            (when
+              (not (and (>= (len v) 5)
+                        (= (slice v 0 5) "_anon")))
+              (append! out v)))
+          vs)
+        out))))
+
+(define
+  dl-rule-check-safety
+  (fn
+    (rule)
+    (let
+      ((head (get rule :head))
+        (body (get rule :body))
+        (bound (list))
+        (err nil))
+      (do
+        (define
+          dl-add-bound!
+          (fn
+            (vs)
+            (for-each
+              (fn
+                (v)
+                (when (not (dl-member-string? v bound)) (append! bound v)))
+              vs)))
+        (define
+          dl-process-eq!
+          (fn
+            (lit)
+            (let
+              ((a (nth lit 1)) (b (nth lit 2)))
+              (let
+                ((va (dl-var? a)) (vb (dl-var? b)))
+                (cond
+                  ((and (not va) (not vb)) nil)
+                  ((and va (not vb))
+                    (dl-add-bound! (list (symbol->string a))))
+                  ((and (not va) vb)
+                    (dl-add-bound! (list (symbol->string b))))
+                  (else
+                    (let
+                      ((sa (symbol->string a)) (sb (symbol->string b)))
+                      (cond
+                        ((dl-member-string? sa bound)
+                          (dl-add-bound! (list sb)))
+                        ((dl-member-string? sb bound)
+                          (dl-add-bound! (list sa)))
+                        (else
+                          (set!
+                            err
+                            (str
+                              "= between two unbound variables "
+                              (list sa sb)
+                              " — at least one must be bound by an "
+                              "earlier positive body literal")))))))))))
+        (define
+          dl-process-cmp!
+          (fn
+            (lit)
+            (let
+              ((needed (dl-vars-of (list (nth lit 1) (nth lit 2)))))
+              (let
+                ((missing (dl-vars-not-in needed bound)))
+                (when
+                  (> (len missing) 0)
+                  (set!
+                    err
+                    (str
+                      "comparison "
+                      (dl-rel-name lit)
+                      " requires bound variable(s) "
+                      missing
+                      " (must be bound by an earlier positive "
+                      "body literal)")))))))
+        (define
+          dl-process-is!
+          (fn
+            (lit)
+            (let
+              ((tgt (nth lit 1)) (expr (nth lit 2)))
+              (let
+                ((needed (dl-vars-of expr)))
+                (let
+                  ((missing (dl-vars-not-in needed bound)))
+                  (cond
+                    ((> (len missing) 0)
+                      (set!
+                        err
+                        (str
+                          "is RHS uses unbound variable(s) "
+                          missing
+                          " — bind them via a prior positive body "
+                          "literal")))
+                    (else
+                      (when
+                        (dl-var? tgt)
+                        (dl-add-bound! (list (symbol->string tgt)))))))))))
+        (define
+          dl-process-neg!
+          (fn
+            (lit)
+            (let
+              ((inner (get lit :neg)))
+              (let
+                ((inner-rn
+                   (cond
+                     ((and (list? inner) (> (len inner) 0))
+                       (dl-rel-name inner))
+                     (else nil)))
+                  ;; Anonymous variables (`_` in source → `_anon*` after
+                  ;; renaming) are existentially quantified within the
+                  ;; negated literal — they don't need to be bound by
+                  ;; an earlier body lit, since `not p(X, _)` is a
+                  ;; valid idiom for "no Y exists s.t. p(X, Y)". Filter
+                  ;; them out of the safety check.
+                  (needed (dl-non-anon-vars (dl-vars-of inner)))
+                  (missing (dl-vars-not-in needed bound)))
+                (cond
+                  ((and (not (nil? inner-rn)) (dl-reserved-rel? inner-rn))
+                    (set! err
+                      (str "negated literal uses reserved name '"
+                           inner-rn
+                           "' — nested `not(...)` / negated built-ins are "
+                           "not supported; introduce an intermediate "
+                           "relation and negate that")))
+                  ((> (len missing) 0)
+                    (set! err
+                      (str "negation refers to unbound variable(s) "
+                           missing
+                           " — they must be bound by an earlier "
+                           "positive body literal"))))))))
+        (define
+          dl-process-agg!
+          (fn
+            (lit)
+            (let
+              ((result-var (nth lit 1)))
+              ;; Aggregate goal vars are existentially quantified within
+              ;; the aggregate; nothing required from outer context. The
+              ;; result var becomes bound after the aggregate fires.
+              (when
+                (dl-var? result-var)
+                (dl-add-bound! (list (symbol->string result-var)))))))
+
+        (define
+          dl-process-lit!
+          (fn
+            (lit)
+            (when
+              (nil? err)
+              (cond
+                ((and (dict? lit) (has-key? lit :neg))
+                  (dl-process-neg! lit))
+                ;; A bare dict that is not a recognised negation is
+                ;; almost certainly a typo (e.g. `{:negs ...}` instead
+                ;; of `{:neg ...}`). Without this guard the dict would
+                ;; silently fall through every clause; the head safety
+                ;; check would then flag the head variables as unbound
+                ;; even though the real bug is the malformed body lit.
+                ((dict? lit)
+                  (set! err
+                    (str "body literal is a dict but lacks :neg — "
+                         "the only dict-shaped body lit recognised is "
+                         "{:neg <positive-lit>} for stratified "
+                         "negation, got " lit)))
+                ((dl-aggregate? lit) (dl-process-agg! lit))
+                ((dl-eq? lit) (dl-process-eq! lit))
+                ((dl-is? lit) (dl-process-is! lit))
+                ((dl-comparison? lit) (dl-process-cmp! lit))
+                ((and (list? lit) (> (len lit) 0))
+                  (let ((rn (dl-rel-name lit)))
+                    (cond
+                      ((and (not (nil? rn)) (dl-reserved-rel? rn))
+                        (set! err
+                          (str "body literal uses reserved name '" rn
+                               "' — built-ins / aggregates have their own "
+                               "syntax; nested `not(...)` is not supported "
+                               "(use stratified negation via an "
+                               "intermediate relation)")))
+                      (else (dl-add-bound! (dl-vars-of lit))))))
+                (else
+                  ;; Anything that's not a dict, not a list, or an
+                  ;; empty list. Numbers / strings / symbols as body
+                  ;; lits don't make sense — surface the type.
+                  (set! err
+                    (str "body literal must be a positive lit, "
+                         "built-in, aggregate, or {:neg ...} dict, "
+                         "got " lit)))))))
+        (for-each dl-process-lit! body)
+        (when
+          (nil? err)
+          (let
+            ((head-vars (dl-vars-of head)) (missing (list)))
+            (do
+              (for-each
+                (fn
+                  (v)
+                  (when
+                    (and (not (dl-member-string? v bound)) (not (= v "_")))
+                    (append! missing v)))
+                head-vars)
+              (when
+                (> (len missing) 0)
+                (set!
+                  err
+                  (str
+                    "head variable(s) "
+                    missing
+                    " do not appear in any positive body literal"))))))
+        err))))

lib/datalog/conformance.conf

@@ -0,0 +1,32 @@
+# Datalog conformance config — sourced by lib/guest/conformance.sh.
+
+LANG_NAME=datalog
+MODE=dict
+
+PRELOADS=(
+  lib/datalog/tokenizer.sx
+  lib/datalog/parser.sx
+  lib/datalog/unify.sx
+  lib/datalog/db.sx
+  lib/datalog/builtins.sx
+  lib/datalog/aggregates.sx
+  lib/datalog/strata.sx
+  lib/datalog/eval.sx
+  lib/datalog/api.sx
+  lib/datalog/magic.sx
+  lib/datalog/demo.sx
+)
+
+SUITES=(
+  "tokenize:lib/datalog/tests/tokenize.sx:(dl-tokenize-tests-run!)"
+  "parse:lib/datalog/tests/parse.sx:(dl-parse-tests-run!)"
+  "unify:lib/datalog/tests/unify.sx:(dl-unify-tests-run!)"
+  "eval:lib/datalog/tests/eval.sx:(dl-eval-tests-run!)"
+  "builtins:lib/datalog/tests/builtins.sx:(dl-builtins-tests-run!)"
+  "semi_naive:lib/datalog/tests/semi_naive.sx:(dl-semi-naive-tests-run!)"
+  "negation:lib/datalog/tests/negation.sx:(dl-negation-tests-run!)"
+  "aggregates:lib/datalog/tests/aggregates.sx:(dl-aggregates-tests-run!)"
+  "api:lib/datalog/tests/api.sx:(dl-api-tests-run!)"
+  "magic:lib/datalog/tests/magic.sx:(dl-magic-tests-run!)"
+  "demo:lib/datalog/tests/demo.sx:(dl-demo-tests-run!)"
+)

lib/datalog/conformance.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+# Thin wrapper — see lib/guest/conformance.sh and lib/datalog/conformance.conf.
+exec bash "$(dirname "$0")/../guest/conformance.sh" "$(dirname "$0")/conformance.conf" "$@"

lib/datalog/datalog.sx

@@ -0,0 +1,97 @@
+;; lib/datalog/datalog.sx — public API documentation index.
+;;
+;; This file is reference-only — `load` is an epoch-protocol command,
+;; not an SX function, so it cannot reload a list of files from inside
+;; another `.sx` file. To set up a fresh sx_server session with all
+;; modules in scope, issue these loads in order:
+;;
+;;   (load "lib/datalog/tokenizer.sx")
+;;   (load "lib/datalog/parser.sx")
+;;   (load "lib/datalog/unify.sx")
+;;   (load "lib/datalog/db.sx")
+;;   (load "lib/datalog/builtins.sx")
+;;   (load "lib/datalog/aggregates.sx")
+;;   (load "lib/datalog/strata.sx")
+;;   (load "lib/datalog/eval.sx")
+;;   (load "lib/datalog/api.sx")
+;;   (load "lib/datalog/magic.sx")
+;;   (load "lib/datalog/demo.sx")
+;;
+;; (lib/datalog/conformance.sh runs this load list automatically.)
+;;
+;; ── Public API surface ─────────────────────────────────────────────
+;;
+;;   Source / data:
+;;     (dl-tokenize "src")              → token list
+;;     (dl-parse "src")                 → parsed clauses
+;;     (dl-program "src")               → db built from a source string
+;;     (dl-program-data facts rules)    → db from SX data lists; rules
+;;                                        accept either dict form or
+;;                                        list form with `<-` arrow
+;;
+;;   Construction (mutates db):
+;;     (dl-make-db)                     empty db
+;;     (dl-add-fact! db lit)            rejects non-ground
+;;     (dl-add-rule! db rule)           rejects unsafe rules
+;;     (dl-rule head body)              dict-rule constructor
+;;     (dl-add-clause! db clause)       parser output → fact or rule
+;;     (dl-load-program! db src)        string source
+;;     (dl-set-strategy! db strategy)   :semi-naive default; :magic
+;;                                        is informational, use
+;;                                        dl-magic-query for actual
+;;                                        magic-sets evaluation
+;;
+;;   Mutation:
+;;     (dl-assert! db lit)              add + re-saturate
+;;     (dl-retract! db lit)             drop EDB, wipe IDB, re-saturate
+;;     (dl-clear-idb! db)               wipe rule-headed relations
+;;
+;;   Query / inspection:
+;;     (dl-saturate! db)                stratified semi-naive default
+;;     (dl-saturate-naive! db)          reference (slow on chains)
+;;     (dl-saturate-rules! db rules)    per-rule-set semi-naive worker
+;;     (dl-query db goal)               list of substitution dicts
+;;     (dl-relation db rel-name)        tuple list for a relation
+;;     (dl-rules db)                    rule list
+;;     (dl-fact-count db)               total ground tuples
+;;     (dl-summary db)                  {<rel>: count} for inspection
+;;
+;;   Single-call convenience:
+;;     (dl-eval source query-source)         parse, run, return substs
+;;     (dl-eval-magic source query-source)   single-goal → magic-sets
+;;
+;;   Magic-sets (lib/datalog/magic.sx):
+;;     (dl-adorn-goal goal)             "b/f" adornment string
+;;     (dl-rule-sips rule head-adn)     SIPS analysis per body lit
+;;     (dl-magic-rewrite rules rel adn args)
+;;                                       rewritten rule list + seed
+;;     (dl-magic-query db query-goal)    end-to-end magic-sets query
+;;
+;; ── Body literal kinds ─────────────────────────────────────────────
+;;
+;;   Positive             (rel arg ... arg)
+;;   Negation             {:neg (rel arg ...)}
+;;   Comparison           (< X Y), (<= X Y), (> X Y), (>= X Y),
+;;                        (= X Y), (!= X Y)
+;;   Arithmetic           (is Z (+ X Y)) and (- * /)
+;;   Aggregation          (count R V Goal),  (sum R V Goal),
+;;                        (min R V Goal),    (max R V Goal),
+;;                        (findall L V Goal)
+;;
+;; ── Variable conventions ───────────────────────────────────────────
+;;
+;;   Variables: SX symbols whose first char is uppercase A–Z or '_'.
+;;   Anonymous '_' is renamed to a fresh _anon<N> per occurrence at
+;;   rule/query load time so multiple '_' don't unify.
+;;
+;; ── Demo programs ──────────────────────────────────────────────────
+;;
+;;   See lib/datalog/demo.sx — federation, content, permissions, and
+;;   the canonical "cooking posts by people I follow (transitively)"
+;;   example.
+;;
+;; ── Status ─────────────────────────────────────────────────────────
+;;
+;;   See plans/datalog-on-sx.md — phase-by-phase progress log and
+;;   roadmap. Run `bash lib/datalog/conformance.sh` to refresh
+;;   `lib/datalog/scoreboard.{json,md}`.

lib/datalog/db.sx

@@ -0,0 +1,575 @@
+;; lib/datalog/db.sx — Datalog database (EDB + IDB + rules) + safety hook.
+;;
+;; A db is a mutable dict:
+;;   {:facts {<rel-name-string> -> (literal ...)}
+;;    :rules ({:head literal :body (literal ...)} ...)}
+;;
+;; Facts are stored as full literals `(rel arg ... arg)` so they unify
+;; directly against rule body literals. Each relation's tuple list is
+;; deduplicated on insert.
+;;
+;; Phase 3 introduced safety analysis for head variables; Phase 4 (in
+;; lib/datalog/builtins.sx) swaps in the real `dl-rule-check-safety`,
+;; which is order-aware and understands built-in predicates.
+
+(define
+  dl-make-db
+  (fn ()
+    {:facts {}
+     :facts-keys {}
+     :facts-index {}
+     :edb-keys {}
+     :rules (list)
+     :strategy :semi-naive}))
+
+;; Record (rel-key, tuple-key) as user-asserted EDB. dl-add-fact! calls
+;; this when an explicit fact is added; the saturator (which uses
+;; dl-add-derived!) does NOT, so derived tuples never appear here.
+;; dl-retract! consults :edb-keys to know which tuples must survive
+;; the wipe-and-resaturate round-trip.
+(define
+  dl-mark-edb!
+  (fn
+    (db rel-key tk)
+    (let
+      ((edb (get db :edb-keys)))
+      (do
+        (when
+          (not (has-key? edb rel-key))
+          (dict-set! edb rel-key {}))
+        (dict-set! (get edb rel-key) tk true)))))
+
+(define
+  dl-edb-fact?
+  (fn
+    (db rel-key tk)
+    (let
+      ((edb (get db :edb-keys)))
+      (and (has-key? edb rel-key)
+           (has-key? (get edb rel-key) tk)))))
+
+;; Evaluation strategy. Default :semi-naive (used by dl-saturate!).
+;; :naive selects dl-saturate-naive! (slower but easier to reason
+;; about). :magic is a marker — goal-directed magic-sets evaluation
+;; is invoked separately via `dl-magic-query`; setting :magic here
+;; is purely informational. Any other value is rejected so typos
+;; don't silently fall back to the default.
+(define
+  dl-strategy-values
+  (list :semi-naive :naive :magic))
+
+(define
+  dl-set-strategy!
+  (fn
+    (db strategy)
+    (cond
+      ((not (dl-keyword-member? strategy dl-strategy-values))
+        (error (str "dl-set-strategy!: unknown strategy " strategy
+                    " — must be one of " dl-strategy-values)))
+      (else
+        (do
+          (dict-set! db :strategy strategy)
+          db)))))
+
+(define
+  dl-keyword-member?
+  (fn
+    (k xs)
+    (cond
+      ((= (len xs) 0) false)
+      ((= k (first xs)) true)
+      (else (dl-keyword-member? k (rest xs))))))
+
+(define
+  dl-get-strategy
+  (fn
+    (db)
+    (if (has-key? db :strategy) (get db :strategy) :semi-naive)))
+
+(define
+  dl-rel-name
+  (fn
+    (lit)
+    (cond
+      ((and (dict? lit) (has-key? lit :neg)) (dl-rel-name (get lit :neg)))
+      ((and (list? lit) (> (len lit) 0) (symbol? (first lit)))
+        (symbol->string (first lit)))
+      (else nil))))
+
+(define dl-builtin-rels (list "<" "<=" ">" ">=" "=" "!=" "is"))
+
+(define
+  dl-member-string?
+  (fn
+    (s xs)
+    (cond
+      ((= (len xs) 0) false)
+      ((= (first xs) s) true)
+      (else (dl-member-string? s (rest xs))))))
+
+(define
+  dl-builtin?
+  (fn
+    (lit)
+    (and
+      (list? lit)
+      (> (len lit) 0)
+      (let
+        ((rel (dl-rel-name lit)))
+        (cond
+          ((nil? rel) false)
+          (else (dl-member-string? rel dl-builtin-rels)))))))
+
+(define
+  dl-positive-lit?
+  (fn
+    (lit)
+    (cond
+      ((and (dict? lit) (has-key? lit :neg)) false)
+      ((dl-builtin? lit) false)
+      ((and (list? lit) (> (len lit) 0)) true)
+      (else false))))
+
+(define
+  dl-tuple-equal?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-tuple-equal-list? a b 0)))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-tuple-equal-list?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-tuple-equal? (nth a i) (nth b i))) false)
+      (else (dl-tuple-equal-list? a b (+ i 1))))))
+
+(define
+  dl-tuple-member?
+  (fn
+    (lit lits)
+    (dl-tuple-member-aux? lit lits 0 (len lits))))
+
+(define
+  dl-tuple-member-aux?
+  (fn
+    (lit lits i n)
+    (cond
+      ((>= i n) false)
+      ((dl-tuple-equal? lit (nth lits i)) true)
+      (else (dl-tuple-member-aux? lit lits (+ i 1) n)))))
+
+(define
+  dl-ensure-rel!
+  (fn
+    (db rel-key)
+    (let
+      ((facts (get db :facts))
+        (fk (get db :facts-keys))
+        (fi (get db :facts-index)))
+      (do
+        (when
+          (not (has-key? facts rel-key))
+          (dict-set! facts rel-key (list)))
+        (when
+          (not (has-key? fk rel-key))
+          (dict-set! fk rel-key {}))
+        (when
+          (not (has-key? fi rel-key))
+          (dict-set! fi rel-key {}))
+        (get facts rel-key)))))
+
+;; First-arg index helpers. Tuples are keyed by their first-after-rel
+;; arg's `(str ...)`; when that arg is a constant, dl-match-positive
+;; uses the index instead of scanning the full relation.
+(define
+  dl-arg-key
+  (fn
+    (v)
+    (str v)))
+
+(define
+  dl-index-add!
+  (fn
+    (db rel-key lit)
+    (let
+      ((idx (get db :facts-index))
+        (n (len lit)))
+      (when
+        (and (>= n 2) (has-key? idx rel-key))
+        (let
+          ((rel-idx (get idx rel-key))
+            (k (dl-arg-key (nth lit 1))))
+          (do
+            (when
+              (not (has-key? rel-idx k))
+              (dict-set! rel-idx k (list)))
+            (append! (get rel-idx k) lit)))))))
+
+(define
+  dl-index-lookup
+  (fn
+    (db rel-key arg-val)
+    (let
+      ((idx (get db :facts-index)))
+      (cond
+        ((not (has-key? idx rel-key)) (list))
+        (else
+          (let ((rel-idx (get idx rel-key))
+                (k (dl-arg-key arg-val)))
+            (if (has-key? rel-idx k) (get rel-idx k) (list))))))))
+
+(define dl-tuple-key (fn (lit) (str lit)))
+
+(define
+  dl-rel-tuples
+  (fn
+    (db rel-key)
+    (let
+      ((facts (get db :facts)))
+      (if (has-key? facts rel-key) (get facts rel-key) (list)))))
+
+;; Reserved relation names: built-in / aggregate / negation / arrow.
+;; Rules and facts may not have these as their head's relation, since
+;; the saturator treats them specially or they are not relation names
+;; at all.
+(define
+  dl-reserved-rel-names
+  (list "not" "count" "sum" "min" "max" "findall" "is"
+        "<" "<=" ">" ">=" "=" "!=" "+" "-" "*" "/" ":-" "?-"))
+
+(define
+  dl-reserved-rel?
+  (fn
+    (name) (dl-member-string? name dl-reserved-rel-names)))
+
+;; Internal: append a derived tuple to :facts without the public
+;; validation pass and without marking :edb-keys. Used by the saturator
+;; (eval.sx) and magic-sets (magic.sx). Returns true if the tuple was
+;; new, false if already present.
+(define
+  dl-add-derived!
+  (fn
+    (db lit)
+    (let
+      ((rel-key (dl-rel-name lit)))
+      (let
+        ((tuples (dl-ensure-rel! db rel-key))
+          (key-dict (get (get db :facts-keys) rel-key))
+          (tk (dl-tuple-key lit)))
+        (cond
+          ((has-key? key-dict tk) false)
+          (else
+            (do
+              (dict-set! key-dict tk true)
+              (append! tuples lit)
+              (dl-index-add! db rel-key lit)
+              true)))))))
+
+;; A simple term — number, string, or symbol — i.e. anything legal
+;; as an EDB fact arg. Compound (list) args belong only in body
+;; literals where they encode arithmetic / aggregate sub-goals.
+(define
+  dl-simple-term?
+  (fn
+    (term)
+    (or (number? term) (string? term) (symbol? term))))
+
+(define
+  dl-args-simple?
+  (fn
+    (lit i n)
+    (cond
+      ((>= i n) true)
+      ((not (dl-simple-term? (nth lit i))) false)
+      (else (dl-args-simple? lit (+ i 1) n)))))
+
+(define
+  dl-add-fact!
+  (fn
+    (db lit)
+    (cond
+      ((not (and (list? lit) (> (len lit) 0)))
+        (error (str "dl-add-fact!: expected literal list, got " lit)))
+      ((dl-reserved-rel? (dl-rel-name lit))
+        (error (str "dl-add-fact!: '" (dl-rel-name lit)
+                    "' is a reserved name (built-in / aggregate / negation)")))
+      ((not (dl-args-simple? lit 1 (len lit)))
+        (error (str "dl-add-fact!: fact args must be numbers, strings, "
+                    "or symbols — compound args (e.g. arithmetic "
+                    "expressions) are body-only and aren't evaluated "
+                    "in fact position. got " lit)))
+      ((not (dl-ground? lit (dl-empty-subst)))
+        (error (str "dl-add-fact!: expected ground literal, got " lit)))
+      (else
+        (let
+          ((rel-key (dl-rel-name lit)) (tk (dl-tuple-key lit)))
+          (do
+            ;; Always mark EDB origin — even if the tuple key was already
+            ;; present (e.g. previously derived), so an explicit assert
+            ;; promotes it to EDB and protects it from the IDB wipe.
+            (dl-mark-edb! db rel-key tk)
+            (dl-add-derived! db lit)))))))
+
+;; The full safety check lives in builtins.sx (it has to know which
+;; predicates are built-ins). dl-add-rule! calls it via forward
+;; reference; load builtins.sx alongside db.sx in any setup that
+;; adds rules. The fallback below is used if builtins.sx isn't loaded.
+(define
+  dl-rule-check-safety
+  (fn
+    (rule)
+    (let
+      ((head-vars (dl-vars-of (get rule :head))) (body-vars (list)))
+      (do
+        (for-each
+          (fn
+            (lit)
+            (when
+              (and
+                (list? lit)
+                (> (len lit) 0)
+                (not (and (dict? lit) (has-key? lit :neg))))
+              (for-each
+                (fn
+                  (v)
+                  (when
+                    (not (dl-member-string? v body-vars))
+                    (append! body-vars v)))
+                (dl-vars-of lit))))
+          (get rule :body))
+        (let
+          ((missing (list)))
+          (do
+            (for-each
+              (fn
+                (v)
+                (when
+                  (and
+                    (not (dl-member-string? v body-vars))
+                    (not (= v "_")))
+                  (append! missing v)))
+              head-vars)
+            (cond
+              ((> (len missing) 0)
+                (str
+                  "head variable(s) "
+                  missing
+                  " do not appear in any body literal"))
+              (else nil))))))))
+
+(define
+  dl-rename-anon-term
+  (fn
+    (term next-name)
+    (cond
+      ((and (symbol? term) (= (symbol->string term) "_"))
+        (next-name))
+      ((list? term)
+        (map (fn (x) (dl-rename-anon-term x next-name)) term))
+      (else term))))
+
+(define
+  dl-rename-anon-lit
+  (fn
+    (lit next-name)
+    (cond
+      ((and (dict? lit) (has-key? lit :neg))
+        {:neg (dl-rename-anon-term (get lit :neg) next-name)})
+      ((list? lit) (dl-rename-anon-term lit next-name))
+      (else lit))))
+
+(define
+  dl-make-anon-renamer
+  (fn
+    (start)
+    (let ((counter start))
+      (fn () (do (set! counter (+ counter 1))
+                 (string->symbol (str "_anon" counter)))))))
+
+;; Scan a rule for variables already named `_anon<N>` (which would
+;; otherwise collide with the renamer's output). Returns the max N
+;; seen, or 0 if none. The renamer then starts at that max + 1, so
+;; freshly-introduced anonymous names can't shadow a user-written
+;; `_anon<N>` symbol.
+(define
+  dl-max-anon-num
+  (fn
+    (term acc)
+    (cond
+      ((symbol? term)
+        (let ((s (symbol->string term)))
+          (cond
+            ((and (>= (len s) 6) (= (slice s 0 5) "_anon"))
+              (let ((n (dl-try-parse-int (slice s 5 (len s)))))
+                (cond
+                  ((nil? n) acc)
+                  ((> n acc) n)
+                  (else acc))))
+            (else acc))))
+      ((dict? term)
+        (cond
+          ((has-key? term :neg)
+            (dl-max-anon-num (get term :neg) acc))
+          (else acc)))
+      ((list? term) (dl-max-anon-num-list term acc 0))
+      (else acc))))
+
+(define
+  dl-max-anon-num-list
+  (fn
+    (xs acc i)
+    (cond
+      ((>= i (len xs)) acc)
+      (else
+        (dl-max-anon-num-list xs (dl-max-anon-num (nth xs i) acc) (+ i 1))))))
+
+;; Cheap "is this string a decimal int" check. Returns the number or
+;; nil. Avoids relying on host parse-number, which on non-int strings
+;; might raise rather than return nil.
+(define
+  dl-try-parse-int
+  (fn
+    (s)
+    (cond
+      ((= (len s) 0) nil)
+      ((not (dl-all-digits? s 0 (len s))) nil)
+      (else (parse-number s)))))
+
+(define
+  dl-all-digits?
+  (fn
+    (s i n)
+    (cond
+      ((>= i n) true)
+      ((let ((c (slice s i (+ i 1))))
+         (not (and (>= c "0") (<= c "9"))))
+        false)
+      (else (dl-all-digits? s (+ i 1) n)))))
+
+(define
+  dl-rename-anon-rule
+  (fn
+    (rule)
+    (let
+      ((start (dl-max-anon-num (get rule :head)
+                (dl-max-anon-num-list (get rule :body) 0 0))))
+      (let ((next-name (dl-make-anon-renamer start)))
+        {:head (dl-rename-anon-term (get rule :head) next-name)
+         :body (map (fn (lit) (dl-rename-anon-lit lit next-name))
+                    (get rule :body))}))))
+
+(define
+  dl-add-rule!
+  (fn
+    (db rule)
+    (cond
+      ((not (dict? rule))
+        (error (str "dl-add-rule!: expected rule dict, got " rule)))
+      ((not (has-key? rule :head))
+        (error (str "dl-add-rule!: rule missing :head, got " rule)))
+      ((not (and (list? (get rule :head))
+                 (> (len (get rule :head)) 0)
+                 (symbol? (first (get rule :head)))))
+        (error (str "dl-add-rule!: head must be a non-empty list "
+                    "starting with a relation-name symbol, got "
+                    (get rule :head))))
+      ((not (dl-args-simple? (get rule :head) 1 (len (get rule :head))))
+        (error (str "dl-add-rule!: rule head args must be variables or "
+                    "constants — compound terms (e.g. `(*(X, 2))`) are "
+                    "not legal in head position; introduce an `is`-bound "
+                    "intermediate in the body. got " (get rule :head))))
+      ((not (list? (if (has-key? rule :body) (get rule :body) (list))))
+        (error (str "dl-add-rule!: body must be a list of literals, got "
+                    (get rule :body))))
+      ((dl-reserved-rel? (dl-rel-name (get rule :head)))
+        (error (str "dl-add-rule!: '" (dl-rel-name (get rule :head))
+                    "' is a reserved name (built-in / aggregate / negation)")))
+      (else
+        (let ((rule (dl-rename-anon-rule rule)))
+          (let
+            ((err (dl-rule-check-safety rule)))
+            (cond
+              ((not (nil? err)) (error (str "dl-add-rule!: " err)))
+              (else
+                (let
+                  ((rules (get db :rules)))
+                  (do (append! rules rule) true))))))))))
+
+(define
+  dl-add-clause!
+  (fn
+    (db clause)
+    (cond
+      ((has-key? clause :query) false)
+      ((and (has-key? clause :body) (= (len (get clause :body)) 0))
+        (dl-add-fact! db (get clause :head)))
+      (else (dl-add-rule! db clause)))))
+
+(define
+  dl-load-program!
+  (fn
+    (db source)
+    (let
+      ((clauses (dl-parse source)))
+      (do (for-each (fn (c) (dl-add-clause! db c)) clauses) db))))
+
+(define
+  dl-program
+  (fn (source) (let ((db (dl-make-db))) (dl-load-program! db source))))
+
+(define dl-rules (fn (db) (get db :rules)))
+
+(define
+  dl-fact-count
+  (fn
+    (db)
+    (let
+      ((facts (get db :facts)) (total 0))
+      (do
+        (for-each
+          (fn (k) (set! total (+ total (len (get facts k)))))
+          (keys facts))
+        total))))
+
+;; Returns {<rel-name>: tuple-count} for debugging. Includes
+;; relations with any tuples plus all rule-head relations (so empty
+;; IDB shows as 0). Skips empty EDB-only entries that are placeholders
+;; from internal `dl-ensure-rel!` calls.
+(define
+  dl-summary
+  (fn
+    (db)
+    (let
+      ((facts (get db :facts))
+        (out {})
+        (rule-heads (list)))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (let ((h (dl-rel-name (get rule :head))))
+              (when
+                (and (not (nil? h)) (not (dl-member-string? h rule-heads)))
+                (append! rule-heads h))))
+          (dl-rules db))
+        (for-each
+          (fn
+            (k)
+            (let ((c (len (get facts k))))
+              (when
+                (or (> c 0) (dl-member-string? k rule-heads))
+                (dict-set! out k c))))
+          (keys facts))
+        ;; Add rule heads that have no facts (yet).
+        (for-each
+          (fn
+            (k)
+            (when (not (has-key? out k)) (dict-set! out k 0)))
+          rule-heads)
+        out))))

lib/datalog/demo.sx

@@ -0,0 +1,162 @@
+;; lib/datalog/demo.sx — example programs over rose-ash-shaped data.
+;;
+;; Phase 10 prototypes Datalog as a rose-ash query language. Wiring
+;; the EDB to actual PostgreSQL is out of scope for this loop (it
+;; would touch service code outside lib/datalog/), but the programs
+;; below show the shape of queries we want, and the test suite runs
+;; them against synthetic in-memory tuples loaded via dl-program-data.
+;;
+;; Seven thematic demos:
+;;
+;;   1. Federation — follow graph, transitive reach, mutuals, FOAF.
+;;   2. Content    — posts, tags, likes, popularity, "for you" feed.
+;;   3. Permissions — group membership and resource access.
+;;   4. Cooking-posts — canonical "posts about cooking by people I
+;;                      follow (transitively)" multi-domain query.
+;;   5. Tag co-occurrence — distinct (T1, T2) pairs with counts.
+;;   6. Shortest path  — weighted-DAG path enumeration + min agg.
+;;   7. Org chart      — transitive subordinate + headcount per mgr.
+
+;; ── Demo 1: federation follow graph ─────────────────────────────
+;; EDB: (follows ACTOR-A ACTOR-B) — A follows B.
+;; IDB:
+;;   (mutual A B)            — A follows B and B follows A
+;;   (reachable A B)         — transitive follow closure
+;;   (foaf A C)              — friend of a friend (mutual filter)
+(define
+  dl-demo-federation-rules
+  (quote
+    ((mutual A B <- (follows A B) (follows B A))
+     (reachable A B <- (follows A B))
+     (reachable A C <- (follows A B) (reachable B C))
+     (foaf A C <- (follows A B) (follows B C) (!= A C)))))
+
+;; ── Demo 2: content recommendation ──────────────────────────────
+;; EDB:
+;;   (authored ACTOR POST)
+;;   (tagged POST TAG)
+;;   (liked ACTOR POST)
+;; IDB:
+;;   (post-likes POST N)            — count of likes per post
+;;   (popular POST)                 — posts with >= 3 likes
+;;   (tagged-by-mutual ACTOR POST)  — post tagged TOPIC by someone
+;;                                    A's mutuals follow.
+(define
+  dl-demo-content-rules
+  (quote
+    ((post-likes P N <- (authored Author P) (count N L (liked L P)))
+     (popular P <- (authored Author P) (post-likes P N) (>= N 3))
+     (interesting Me P
+       <-
+       (follows Me Buddy)
+       (authored Buddy P)
+       (popular P)))))
+
+;; ── Demo 3: role-based permissions ──────────────────────────────
+;; EDB:
+;;   (member ACTOR GROUP)
+;;   (subgroup CHILD PARENT)
+;;   (allowed GROUP RESOURCE)
+;; IDB:
+;;   (in-group ACTOR GROUP)         — direct or via subgroup chain
+;;   (can-access ACTOR RESOURCE)    — actor inherits group permission
+(define
+  dl-demo-perm-rules
+  (quote
+    ((in-group A G <- (member A G))
+     (in-group A G <- (member A H) (subgroup-trans H G))
+     (subgroup-trans X Y <- (subgroup X Y))
+     (subgroup-trans X Z <- (subgroup X Y) (subgroup-trans Y Z))
+     (can-access A R <- (in-group A G) (allowed G R)))))
+
+;; ── Demo 4: cooking-posts (the canonical Phase 10 query) ────────
+;; "Posts about cooking by people I follow (transitively)."
+;; Combines federation (follows + transitive reach), authoring,
+;; tagging — the rose-ash multi-domain join.
+;;
+;; EDB:
+;;   (follows ACTOR-A ACTOR-B)
+;;   (authored ACTOR POST)
+;;   (tagged POST TAG)
+(define
+  dl-demo-cooking-rules
+  (quote
+    ((reach Me Them <- (follows Me Them))
+     (reach Me Them <- (follows Me X) (reach X Them))
+     (cooking-post-by-network Me P
+       <-
+       (reach Me Author)
+       (authored Author P)
+       (tagged P cooking)))))
+
+;; ── Demo 5: tag co-occurrence ───────────────────────────────────
+;; "Posts tagged with both T1 AND T2." Useful for narrowed-down
+;; recommendations like "vegetarian cooking" posts.
+;;
+;; EDB:
+;;   (tagged POST TAG)
+;; IDB:
+;;   (cotagged POST T1 T2)        — post has both T1 and T2 (T1 != T2)
+;;   (popular-pair T1 T2 N)       — count of posts cotagged (T1, T2)
+(define
+  dl-demo-tag-cooccur-rules
+  (quote
+    ((cotagged P T1 T2 <- (tagged P T1) (tagged P T2) (!= T1 T2))
+     ;; Distinct (T1, T2) pairs that occur somewhere.
+     (tag-pair T1 T2 <- (cotagged P T1 T2))
+     (tag-pair-count T1 T2 N
+       <-
+       (tag-pair T1 T2)
+       (count N P (cotagged P T1 T2))))))
+
+;; ── Demo 6: weighted-DAG shortest path ─────────────────────────
+;; "What's the cheapest way from X to Y?" Edge weights with `is`
+;; arithmetic to sum costs, then `min` aggregation to pick the
+;; shortest. Termination requires the graph to be a DAG (cycles
+;; would produce infinite distances without a bound; programs
+;; built on this should add a depth filter `(<, D, MAX)` if cycles
+;; are possible).
+;;
+;; EDB:
+;;   (edge FROM TO COST)
+;; IDB:
+;;   (path FROM TO COST)            — any path
+;;   (shortest FROM TO COST)        — minimum cost path
+(define
+  dl-demo-shortest-path-rules
+  (quote
+    ((path X Y W <- (edge X Y W))
+     (path X Z W
+       <-
+       (edge X Y W1)
+       (path Y Z W2)
+       (is W (+ W1 W2)))
+     (shortest X Y W <- (path X Y _) (min W C (path X Y C))))))
+
+;; ── Demo 7: org chart + transitive headcount ───────────────────
+;; Manager graph: each employee has a single manager. Compute the
+;; transitive subordinate set and headcount per manager.
+;;
+;; EDB:
+;;   (manager EMP MGR)            — EMP reports directly to MGR
+;; IDB:
+;;   (subordinate MGR EMP)        — EMP is in MGR's subtree
+;;   (headcount MGR N)            — number of subordinates under MGR
+(define
+  dl-demo-org-rules
+  (quote
+    ((subordinate Mgr Emp <- (manager Emp Mgr))
+     (subordinate Mgr Emp
+       <- (manager Mid Mgr) (subordinate Mid Emp))
+     (headcount Mgr N
+       <- (subordinate Mgr Anyone) (count N E (subordinate Mgr E))))))
+
+;; ── Loader stub ──────────────────────────────────────────────────
+;; Wiring to PostgreSQL would replace these helpers with calls into
+;; rose-ash's internal HTTP RPC (fetch_data → /internal/data/...).
+;; The shape returned by dl-load-from-edb! is the same in either case.
+(define
+  dl-demo-make
+  (fn
+    (facts rules)
+    (dl-program-data facts rules)))

lib/datalog/eval.sx

@@ -0,0 +1,512 @@
+;; lib/datalog/eval.sx — fixpoint evaluator (naive + semi-naive).
+;;
+;; Two saturators are exposed:
+;;   `dl-saturate-naive!` — re-joins each rule against the full DB every
+;;     iteration. Reference implementation; useful for differential tests.
+;;   `dl-saturate!`       — semi-naive default. Tracks per-relation delta
+;;     sets and substitutes one positive body literal per rule with the
+;;     delta of its relation, joining the rest against the previous-
+;;     iteration DB. Same fixpoint, dramatically less work on recursive
+;;     rules.
+;;
+;; Body literal kinds:
+;;   positive (rel arg ... arg)  → match against EDB+IDB tuples
+;;   built-in (< X Y), (is X e)  → constraint via dl-eval-builtin
+;;   negation {:neg lit}         → Phase 7
+
+(define
+  dl-match-positive
+  (fn
+    (lit db subst)
+    (let
+      ((rel (dl-rel-name lit)) (results (list)))
+      (cond
+        ((nil? rel) (error (str "dl-match-positive: bad literal " lit)))
+        (else
+          (let
+            ;; If the first argument walks to a non-variable (constant
+            ;; or already-bound var), use the first-arg index for
+            ;; this relation. Otherwise scan the full tuple list.
+            ((tuples
+               (cond
+                 ((>= (len lit) 2)
+                   (let ((walked (dl-walk (nth lit 1) subst)))
+                     (cond
+                       ((dl-var? walked) (dl-rel-tuples db rel))
+                       (else (dl-index-lookup db rel walked)))))
+                 (else (dl-rel-tuples db rel)))))
+            (do
+              (for-each
+                (fn
+                  (tuple)
+                  (let
+                    ((s (dl-unify lit tuple subst)))
+                    (when (not (nil? s)) (append! results s))))
+                tuples)
+              results)))))))
+
+;; Match a positive literal against the delta set for its relation only.
+(define
+  dl-match-positive-delta
+  (fn
+    (lit delta subst)
+    (let
+      ((rel (dl-rel-name lit)) (results (list)))
+      (let
+        ((tuples (if (has-key? delta rel) (get delta rel) (list))))
+        (do
+          (for-each
+            (fn
+              (tuple)
+              (let
+                ((s (dl-unify lit tuple subst)))
+                (when (not (nil? s)) (append! results s))))
+            tuples)
+          results)))))
+
+;; Naive matcher (for dl-saturate-naive! and dl-query post-saturation).
+(define
+  dl-match-negation
+  (fn
+    (inner db subst)
+    (let
+      ((walked (dl-apply-subst inner subst))
+        (matches (dl-match-positive inner db subst)))
+      (cond
+        ((= (len matches) 0) (list subst))
+        (else (list))))))
+
+(define
+  dl-match-lit
+  (fn
+    (lit db subst)
+    (cond
+      ((and (dict? lit) (has-key? lit :neg))
+        (dl-match-negation (get lit :neg) db subst))
+      ((dl-aggregate? lit) (dl-eval-aggregate lit db subst))
+      ((dl-builtin? lit)
+        (let
+          ((s (dl-eval-builtin lit subst)))
+          (if (nil? s) (list) (list s))))
+      ((and (list? lit) (> (len lit) 0))
+        (dl-match-positive lit db subst))
+      (else (error (str "datalog: unknown body-literal shape: " lit))))))
+
+(define
+  dl-find-bindings
+  (fn (lits db subst) (dl-fb-aux lits db subst 0 (len lits))))
+
+(define
+  dl-fb-aux
+  (fn
+    (lits db subst i n)
+    (cond
+      ((nil? subst) (list))
+      ((>= i n) (list subst))
+      (else
+        (let
+          ((options (dl-match-lit (nth lits i) db subst))
+            (results (list)))
+          (do
+            (for-each
+              (fn
+                (s)
+                (for-each
+                  (fn (s2) (append! results s2))
+                  (dl-fb-aux lits db s (+ i 1) n)))
+              options)
+            results))))))
+
+;; Naive: apply each rule against full DB until no new tuples.
+(define
+  dl-apply-rule!
+  (fn
+    (db rule)
+    (let
+      ((head (get rule :head)) (body (get rule :body)) (new? false))
+      (do
+        (for-each
+          (fn
+            (s)
+            (let
+              ((derived (dl-apply-subst head s)))
+              (when (dl-add-derived! db derived) (set! new? true))))
+          (dl-find-bindings body db (dl-empty-subst)))
+        new?))))
+
+;; Returns true iff one more saturation step would derive no new
+;; tuples (i.e. the db is at fixpoint). Useful in tests that want
+;; to assert "no work left" after a saturation call. Works under
+;; either saturator since both compute the same fixpoint.
+(define
+  dl-saturated?
+  (fn
+    (db)
+    (let ((any-new false))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (when (not any-new)
+              (for-each
+                (fn
+                  (s)
+                  (let ((derived (dl-apply-subst (get rule :head) s)))
+                    (when
+                      (and (not any-new)
+                           (not (dl-tuple-member?
+                                  derived
+                                  (dl-rel-tuples
+                                    db (dl-rel-name derived)))))
+                      (set! any-new true))))
+                (dl-find-bindings (get rule :body) db (dl-empty-subst)))))
+          (dl-rules db))
+        (not any-new)))))
+
+(define
+  dl-saturate-naive!
+  (fn
+    (db)
+    (let
+      ((changed true))
+      (do
+        (define
+          dl-snloop
+          (fn
+            ()
+            (when
+              changed
+              (do
+                (set! changed false)
+                (for-each
+                  (fn (r) (when (dl-apply-rule! db r) (set! changed true)))
+                  (dl-rules db))
+                (dl-snloop)))))
+        (dl-snloop)
+        db))))
+
+;; ── Semi-naive ───────────────────────────────────────────────────
+
+;; Take a snapshot dict {rel -> tuples} of every relation currently in
+;; the DB. Used as initial delta for the first iteration.
+(define
+  dl-snapshot-facts
+  (fn
+    (db)
+    (let
+      ((facts (get db :facts)) (out {}))
+      (do
+        (for-each
+          (fn (k) (dict-set! out k (dl-copy-list (get facts k))))
+          (keys facts))
+        out))))
+
+(define
+  dl-copy-list
+  (fn
+    (xs)
+    (let
+      ((out (list)))
+      (do (for-each (fn (x) (append! out x)) xs) out))))
+
+;; Does any relation in `delta` have ≥1 tuple?
+(define
+  dl-delta-empty?
+  (fn
+    (delta)
+    (let
+      ((ks (keys delta)) (any-non-empty false))
+      (do
+        (for-each
+          (fn
+            (k)
+            (when
+              (> (len (get delta k)) 0)
+              (set! any-non-empty true)))
+          ks)
+        (not any-non-empty)))))
+
+;; Find substitutions such that `lits` are all satisfied AND `delta-idx`
+;; is matched against the per-relation delta only. The other positive
+;; literals match against the snapshot DB (db.facts read at iteration
+;; start). Built-ins and negations behave as in `dl-match-lit`.
+(define
+  dl-find-bindings-semi
+  (fn
+    (lits db delta delta-idx subst)
+    (dl-fbs-aux lits db delta delta-idx 0 subst)))
+
+(define
+  dl-fbs-aux
+  (fn
+    (lits db delta delta-idx i subst)
+    (cond
+      ((nil? subst) (list))
+      ((>= i (len lits)) (list subst))
+      (else
+        (let
+          ((lit (nth lits i))
+            (options
+              (cond
+                ((and (dict? lit) (has-key? lit :neg))
+                  (dl-match-negation (get lit :neg) db subst))
+                ((dl-aggregate? lit) (dl-eval-aggregate lit db subst))
+                ((dl-builtin? lit)
+                  (let
+                    ((s (dl-eval-builtin lit subst)))
+                    (if (nil? s) (list) (list s))))
+                ((and (list? lit) (> (len lit) 0))
+                  (if
+                    (= i delta-idx)
+                    (dl-match-positive-delta lit delta subst)
+                    (dl-match-positive lit db subst)))
+                (else (error (str "datalog: unknown body-lit: " lit)))))
+            (results (list)))
+          (do
+            (for-each
+              (fn
+                (s)
+                (for-each
+                  (fn (s2) (append! results s2))
+                  (dl-fbs-aux lits db delta delta-idx (+ i 1) s)))
+              options)
+            results))))))
+
+;; Collect candidate head tuples from a rule using delta. Walks every
+;; positive body position and unions the resulting heads. For rules
+;; with no positive body literal, falls back to a naive single-pass
+;; (so static facts like `(p X) :- (= X 5).` derive on iteration 1).
+(define
+  dl-collect-rule-candidates
+  (fn
+    (rule db delta)
+    (let
+      ((head (get rule :head))
+        (body (get rule :body))
+        (out (list))
+        (saw-pos false))
+      (do
+        (define
+          dl-cri
+          (fn
+            (i)
+            (when
+              (< i (len body))
+              (do
+                (let
+                  ((lit (nth body i)))
+                  (when
+                    (dl-positive-lit? lit)
+                    (do
+                      (set! saw-pos true)
+                      (for-each
+                        (fn (s) (append! out (dl-apply-subst head s)))
+                        (dl-find-bindings-semi
+                          body
+                          db
+                          delta
+                          i
+                          (dl-empty-subst))))))
+                (dl-cri (+ i 1))))))
+        (dl-cri 0)
+        (when
+          (not saw-pos)
+          (for-each
+            (fn (s) (append! out (dl-apply-subst head s)))
+            (dl-find-bindings body db (dl-empty-subst))))
+        out))))
+
+;; Add a list of candidate tuples to db; collect newly-added ones into
+;; the new-delta dict (keyed by relation name).
+(define
+  dl-commit-candidates!
+  (fn
+    (db candidates new-delta)
+    (for-each
+      (fn
+        (lit)
+        (when
+          (dl-add-derived! db lit)
+          (let
+            ((rel (dl-rel-name lit)))
+            (do
+              (when
+                (not (has-key? new-delta rel))
+                (dict-set! new-delta rel (list)))
+              (append! (get new-delta rel) lit)))))
+      candidates)))
+
+(define
+  dl-saturate-rules!
+  (fn
+    (db rules)
+    (let
+      ((delta (dl-snapshot-facts db)))
+      (do
+        (define
+          dl-sr-step
+          (fn
+            ()
+            (let
+              ((pending (list)) (new-delta {}))
+              (do
+                (for-each
+                  (fn
+                    (rule)
+                    (for-each
+                      (fn (cand) (append! pending cand))
+                      (dl-collect-rule-candidates rule db delta)))
+                  rules)
+                (dl-commit-candidates! db pending new-delta)
+                (cond
+                  ((dl-delta-empty? new-delta) nil)
+                  (else (do (set! delta new-delta) (dl-sr-step))))))))
+        (dl-sr-step)
+        db))))
+
+;; Stratified driver: rejects non-stratifiable programs at saturation
+;; time, then iterates strata in increasing order, running semi-naive on
+;; the rules whose head sits in that stratum.
+(define
+  dl-saturate!
+  (fn
+    (db)
+    (let
+      ((err (dl-check-stratifiable db)))
+      (cond
+        ((not (nil? err)) (error (str "dl-saturate!: " err)))
+        (else
+          (let
+            ((strata (dl-compute-strata db)))
+            (let
+              ((grouped (dl-group-rules-by-stratum db strata)))
+              (let
+                ((groups (get grouped :groups))
+                  (max-s (get grouped :max)))
+                (do
+                  (define
+                    dl-strat-loop
+                    (fn
+                      (s)
+                      (when
+                        (<= s max-s)
+                        (let
+                          ((sk (str s)))
+                          (do
+                            (when
+                              (has-key? groups sk)
+                              (dl-saturate-rules! db (get groups sk)))
+                            (dl-strat-loop (+ s 1)))))))
+                  (dl-strat-loop 0)
+                  db)))))))))
+
+;; ── Querying ─────────────────────────────────────────────────────
+
+;; Coerce a query argument to a list of body literals. A single literal
+;; like `(p X)` (positive — head is a symbol) or `{:neg ...}` becomes
+;; `((p X))`. A list of literals like `((p X) (q X))` is returned as-is.
+(define
+  dl-query-coerce
+  (fn
+    (goal)
+    (cond
+      ((and (dict? goal) (has-key? goal :neg)) (list goal))
+      ((and (list? goal) (> (len goal) 0) (symbol? (first goal)))
+        (list goal))
+      ((list? goal) goal)
+      (else (error (str "dl-query: unrecognised goal shape: " goal))))))
+
+(define
+  dl-query
+  (fn
+    (db goal)
+    (do
+      (dl-saturate! db)
+      ;; Rename anonymous '_' vars in each goal literal so multiple
+      ;; occurrences do not unify together. Keep the user-facing var
+      ;; list (taken before renaming) so projected results retain user
+      ;; names.
+      (let
+        ((goals (dl-query-coerce goal))
+          ;; Start the renamer past any `_anon<N>` symbols the user
+          ;; may have written in the query — avoids collision.
+          (renamer
+            (dl-make-anon-renamer (dl-max-anon-num-list goal 0 0))))
+        (let
+          ((user-vars (dl-query-user-vars goals))
+            (renamed (map (fn (g) (dl-rename-anon-lit g renamer)) goals)))
+          (let
+            ((substs (dl-find-bindings renamed db (dl-empty-subst)))
+              (results (list)))
+            (do
+              (for-each
+                (fn
+                  (s)
+                  (let
+                    ((proj (dl-project-subst s user-vars)))
+                    (when
+                      (not (dl-tuple-member? proj results))
+                      (append! results proj))))
+                substs)
+              results)))))))
+
+(define
+  dl-query-user-vars
+  (fn
+    (goals)
+    (let ((seen (list)))
+      (do
+        (for-each
+          (fn
+            (g)
+            (cond
+              ((and (dict? g) (has-key? g :neg))
+                (for-each
+                  (fn
+                    (v)
+                    (when
+                      (and (not (= v "_")) (not (dl-member-string? v seen)))
+                      (append! seen v)))
+                  (dl-vars-of (get g :neg))))
+              ((dl-aggregate? g)
+                ;; Only the result var (first arg of the aggregate
+                ;; literal) is user-facing. The aggregated var and
+                ;; any vars in the inner goal are internal.
+                (let ((r (nth g 1)))
+                  (when
+                    (dl-var? r)
+                    (let ((rn (symbol->string r)))
+                      (when
+                        (and (not (= rn "_"))
+                             (not (dl-member-string? rn seen)))
+                        (append! seen rn))))))
+              (else
+                (for-each
+                  (fn
+                    (v)
+                    (when
+                      (and (not (= v "_")) (not (dl-member-string? v seen)))
+                      (append! seen v)))
+                  (dl-vars-of g)))))
+          goals)
+        seen))))
+
+(define
+  dl-project-subst
+  (fn
+    (subst names)
+    (let
+      ((out {}))
+      (do
+        (for-each
+          (fn
+            (n)
+            (let
+              ((sym (string->symbol n)))
+              (let
+                ((v (dl-walk sym subst)))
+                (dict-set! out n (dl-apply-subst v subst)))))
+          names)
+        out))))
+
+(define dl-relation (fn (db name) (dl-rel-tuples db name)))

lib/datalog/magic.sx

@@ -0,0 +1,464 @@
+;; lib/datalog/magic.sx — adornment analysis + sideways info passing.
+;;
+;; First step of the magic-sets transformation (Phase 6). Right now
+;; the saturator does not consume these — they are introspection
+;; helpers that future magic-set rewriting will build on top of.
+;;
+;; Definitions:
+;;   - An *adornment* of an n-ary literal is an n-character string
+;;     of "b" (bound — value already known at the call site) and
+;;     "f" (free — to be derived).
+;;   - SIPS (Sideways Information Passing Strategy) walks the body
+;;     of an adorned rule left-to-right tracking which variables
+;;     have been bound so far, computing each body literal's
+;;     adornment in turn.
+;;
+;; Usage:
+;;
+;;   (dl-adorn-goal '(ancestor tom X))
+;;     => "bf"
+;;
+;;   (dl-rule-sips
+;;     {:head (ancestor X Z)
+;;      :body ((parent X Y) (ancestor Y Z))}
+;;     "bf")
+;;   => ({:lit (parent X Y) :adornment "bf"}
+;;       {:lit (ancestor Y Z) :adornment "bf"})
+
+;; Per-arg adornment under the current bound-var name set.
+(define
+  dl-adorn-arg
+  (fn
+    (arg bound)
+    (cond
+      ((dl-var? arg)
+        (if (dl-member-string? (symbol->string arg) bound) "b" "f"))
+      (else "b"))))
+
+;; Adornment for the args of a literal (after the relation name).
+(define
+  dl-adorn-args
+  (fn
+    (args bound)
+    (cond
+      ((= (len args) 0) "")
+      (else
+        (str
+          (dl-adorn-arg (first args) bound)
+          (dl-adorn-args (rest args) bound))))))
+
+;; Adornment of a top-level goal under the empty bound-var set.
+(define
+  dl-adorn-goal
+  (fn (goal) (dl-adorn-args (rest goal) (list))))
+
+;; Adornment of a literal under an explicit bound set.
+(define
+  dl-adorn-lit
+  (fn (lit bound) (dl-adorn-args (rest lit) bound)))
+
+;; The set of variable names made bound by walking a positive
+;; literal whose adornment is known. Free positions add their
+;; vars to the bound set.
+(define
+  dl-vars-bound-by-lit
+  (fn
+    (lit bound)
+    (let ((args (rest lit)) (out (list)))
+      (do
+        (for-each
+          (fn (a)
+            (when
+              (and (dl-var? a)
+                   (not (dl-member-string? (symbol->string a) bound))
+                   (not (dl-member-string? (symbol->string a) out)))
+              (append! out (symbol->string a))))
+          args)
+        out))))
+
+;; Walk the rule body left-to-right tracking bound vars seeded by the
+;; head adornment. Returns a list of {:lit :adornment} entries.
+;;
+;; Negation, comparison, and built-ins are passed through with their
+;; adornment computed from the current bound set; they don't add new
+;; bindings (except `is`, which binds its left arg if a var). Aggregates
+;; are treated like is — the result var becomes bound.
+(define
+  dl-init-head-bound
+  (fn
+    (head adornment)
+    (let ((args (rest head)) (out (list)))
+      (do
+        (define
+          dl-ihb-loop
+          (fn
+            (i)
+            (when
+              (< i (len args))
+              (do
+                (let
+                  ((c (slice adornment i (+ i 1)))
+                    (a (nth args i)))
+                  (when
+                    (and (= c "b") (dl-var? a))
+                    (let ((n (symbol->string a)))
+                      (when
+                        (not (dl-member-string? n out))
+                        (append! out n)))))
+                (dl-ihb-loop (+ i 1))))))
+        (dl-ihb-loop 0)
+        out))))
+
+(define
+  dl-rule-sips
+  (fn
+    (rule head-adornment)
+    (let
+      ((bound (dl-init-head-bound (get rule :head) head-adornment))
+        (out (list)))
+      (do
+        (for-each
+          (fn
+            (lit)
+            (cond
+              ((and (dict? lit) (has-key? lit :neg))
+                (let ((target (get lit :neg)))
+                  (append!
+                    out
+                    {:lit lit :adornment (dl-adorn-lit target bound)})))
+              ((dl-builtin? lit)
+                (let ((adn (dl-adorn-lit lit bound)))
+                  (do
+                    (append! out {:lit lit :adornment adn})
+                    ;; `is` binds its left arg (if var) once RHS is ground.
+                    (when
+                      (and (= (dl-rel-name lit) "is") (dl-var? (nth lit 1)))
+                      (let ((n (symbol->string (nth lit 1))))
+                        (when
+                          (not (dl-member-string? n bound))
+                          (append! bound n)))))))
+              ((and (list? lit) (dl-aggregate? lit))
+                (let ((adn (dl-adorn-lit lit bound)))
+                  (do
+                    (append! out {:lit lit :adornment adn})
+                    ;; Result var (first arg) becomes bound.
+                    (when (dl-var? (nth lit 1))
+                      (let ((n (symbol->string (nth lit 1))))
+                        (when
+                          (not (dl-member-string? n bound))
+                          (append! bound n)))))))
+              ((and (list? lit) (> (len lit) 0))
+                (let ((adn (dl-adorn-lit lit bound)))
+                  (do
+                    (append! out {:lit lit :adornment adn})
+                    (for-each
+                      (fn (n)
+                        (when (not (dl-member-string? n bound))
+                          (append! bound n)))
+                      (dl-vars-bound-by-lit lit bound)))))))
+          (get rule :body))
+        out))))
+
+;; ── Magic predicate naming + bound-args extraction ─────────────
+;; These are building blocks for the magic-sets *transformation*
+;; itself. The transformation (which generates rewritten rules
+;; with magic_<rel>^<adornment> filters) is future work — for now
+;; these helpers can be used to inspect what such a transformation
+;; would produce.
+
+;; "magic_p^bf" given relation "p" and adornment "bf".
+(define
+  dl-magic-rel-name
+  (fn (rel adornment) (str "magic_" rel "^" adornment)))
+
+;; A magic predicate literal:
+;;   (magic_<rel>^<adornment> arg1 arg2 ...)
+(define
+  dl-magic-lit
+  (fn
+    (rel adornment bound-args)
+    (cons (string->symbol (dl-magic-rel-name rel adornment)) bound-args)))
+
+;; Extract bound args (those at "b" positions in `adornment`) from a
+;; literal `(rel arg1 arg2 ... argN)`. Returns the list of arg values.
+(define
+  dl-bound-args
+  (fn
+    (lit adornment)
+    (let ((args (rest lit)) (out (list)))
+      (do
+        (define
+          dl-ba-loop
+          (fn
+            (i)
+            (when
+              (< i (len args))
+              (do
+                (when
+                  (= (slice adornment i (+ i 1)) "b")
+                  (append! out (nth args i)))
+                (dl-ba-loop (+ i 1))))))
+        (dl-ba-loop 0)
+        out))))
+
+;; ── Magic-sets rewriter ─────────────────────────────────────────
+;;
+;; Given the original rule list and a query (rel, adornment) pair,
+;; generates the magic-rewritten program: a list of rules that
+;; (a) gate each original rule with a `magic_<rel>^<adn>` filter and
+;; (b) propagate the magic relation through SIPS so that only
+;; query-relevant tuples are derived. Seed facts are returned
+;; separately and must be added to the db at evaluation time.
+;;
+;; Output: {:rules <rewritten-rules> :seed <magic-seed-literal>}
+;;
+;; The rewriter only rewrites IDB rules; EDB facts pass through.
+;; Built-in predicates and negation in body literals are kept in
+;; place but do not generate propagation rules of their own.
+
+(define
+  dl-magic-pair-key
+  (fn (rel adornment) (str rel "^" adornment)))
+
+(define
+  dl-magic-rewrite
+  (fn
+    (rules query-rel query-adornment query-args)
+    (let
+      ((seen (list))
+        (queue (list))
+        (out (list)))
+      (do
+        (define
+          dl-mq-mark!
+          (fn
+            (rel adornment)
+            (let ((k (dl-magic-pair-key rel adornment)))
+              (when
+                (not (dl-member-string? k seen))
+                (do
+                  (append! seen k)
+                  (append! queue {:rel rel :adn adornment}))))))
+
+        (define
+          dl-mq-rewrite-rule!
+          (fn
+            (rule adn)
+            (let
+              ((head (get rule :head))
+                (body (get rule :body))
+                (sips (dl-rule-sips rule adn)))
+              (let
+                ((magic-filter
+                   (dl-magic-lit
+                     (dl-rel-name head)
+                     adn
+                     (dl-bound-args head adn))))
+                (do
+                  ;; Adorned rule: head :- magic-filter, body...
+                  (let ((new-body (list)))
+                    (do
+                      (append! new-body magic-filter)
+                      (for-each
+                        (fn (lit) (append! new-body lit))
+                        body)
+                      (append! out {:head head :body new-body})))
+                  ;; Propagation rules for each positive non-builtin
+                  ;; body literal at position i.
+                  (define
+                    dl-mq-prop-loop
+                    (fn
+                      (i)
+                      (when
+                        (< i (len body))
+                        (do
+                          (let
+                            ((lit (nth body i))
+                              (sip-entry (nth sips i)))
+                            (when
+                              (and (list? lit)
+                                   (> (len lit) 0)
+                                   (not (and (dict? lit) (has-key? lit :neg)))
+                                   (not (dl-builtin? lit))
+                                   (not (dl-aggregate? lit)))
+                              (let
+                                ((lit-adn (get sip-entry :adornment))
+                                  (lit-rel (dl-rel-name lit)))
+                                (let
+                                  ((prop-head
+                                     (dl-magic-lit
+                                       lit-rel
+                                       lit-adn
+                                       (dl-bound-args lit lit-adn))))
+                                  (let ((prop-body (list)))
+                                    (do
+                                      (append! prop-body magic-filter)
+                                      (define
+                                        dl-mq-prefix-loop
+                                        (fn
+                                          (j)
+                                          (when
+                                            (< j i)
+                                            (do
+                                              (append!
+                                                prop-body
+                                                (nth body j))
+                                              (dl-mq-prefix-loop (+ j 1))))))
+                                      (dl-mq-prefix-loop 0)
+                                      (append!
+                                        out
+                                        {:head prop-head :body prop-body})
+                                      (dl-mq-mark! lit-rel lit-adn)))))))
+                          (dl-mq-prop-loop (+ i 1))))))
+                  (dl-mq-prop-loop 0))))))
+
+        (dl-mq-mark! query-rel query-adornment)
+
+        (let ((idx 0))
+          (define
+            dl-mq-process
+            (fn
+              ()
+              (when
+                (< idx (len queue))
+                (let ((item (nth queue idx)))
+                  (do
+                    (set! idx (+ idx 1))
+                    (let
+                      ((rel (get item :rel)) (adn (get item :adn)))
+                      (for-each
+                        (fn
+                          (rule)
+                          (when
+                            (= (dl-rel-name (get rule :head)) rel)
+                            (dl-mq-rewrite-rule! rule adn)))
+                        rules))
+                    (dl-mq-process))))))
+          (dl-mq-process))
+
+        {:rules out
+         :seed
+         (dl-magic-lit
+           query-rel
+           query-adornment
+           query-args)}))))
+
+;; ── Top-level magic-sets driver ─────────────────────────────────
+;;
+;; (dl-magic-query db query-goal) — run `query-goal` under magic-sets
+;; evaluation. Builds a fresh internal db with:
+;;   - the caller's EDB facts (relations not headed by any rule),
+;;   - the magic seed fact, and
+;;   - the rewritten rules.
+;; Saturates and queries, returning the substitution list. The
+;; caller's db is untouched.
+;;
+;; Useful primarily as a perf alternative for queries that only
+;; need a small slice of a recursive relation. Equivalent to
+;; dl-query for any single fully-stratifiable program.
+
+(define
+  dl-magic-rule-heads
+  (fn
+    (rules)
+    (let ((seen (list)))
+      (do
+        (for-each
+          (fn
+            (r)
+            (let ((h (dl-rel-name (get r :head))))
+              (when
+                (and (not (nil? h)) (not (dl-member-string? h seen)))
+                (append! seen h))))
+          rules)
+        seen))))
+
+;; True iff any rule's body contains a literal kind that the magic
+;; rewriter doesn't propagate magic to — i.e. an aggregate or a
+;; negation. Used by dl-magic-query to decide whether to pre-saturate
+;; the source db (for correctness on stratified programs) or skip
+;; that step (preserving full magic-sets efficiency for pure
+;; positive programs).
+(define
+  dl-rule-has-nonprop-lit?
+  (fn
+    (body i n)
+    (cond
+      ((>= i n) false)
+      ((let ((lit (nth body i)))
+         (or (and (dict? lit) (has-key? lit :neg))
+             (dl-aggregate? lit)))
+        true)
+      (else (dl-rule-has-nonprop-lit? body (+ i 1) n)))))
+
+(define
+  dl-rules-need-presaturation?
+  (fn
+    (rules)
+    (cond
+      ((= (len rules) 0) false)
+      ((let ((body (get (first rules) :body)))
+         (dl-rule-has-nonprop-lit? body 0 (len body)))
+        true)
+      (else (dl-rules-need-presaturation? (rest rules))))))
+
+(define
+  dl-magic-query
+  (fn
+    (db query-goal)
+    ;; Magic-sets only applies to positive non-builtin / non-aggregate
+    ;; literals against rule-defined relations. For other goal shapes
+    ;; (built-ins, aggregates, EDB-only relations) the seed is either
+    ;; non-ground or unused; fall back to dl-query.
+    (cond
+      ((not (and (list? query-goal)
+                 (> (len query-goal) 0)
+                 (symbol? (first query-goal))))
+        (error (str "dl-magic-query: goal must be a positive literal "
+                    "(non-empty list with a symbol head), got " query-goal)))
+      ((or (dl-builtin? query-goal)
+           (dl-aggregate? query-goal)
+           (and (dict? query-goal) (has-key? query-goal :neg)))
+        (dl-query db query-goal))
+      (else
+        (do
+          ;; If the rule set has aggregates or negation, pre-saturate
+          ;; the source db before copying facts. The magic rewriter
+          ;; passes aggregate body lits and negated lits through
+          ;; unchanged (no magic propagation generated for them) — so
+          ;; if their inner-goal relation is IDB, it would be empty in
+          ;; the magic db. Pre-saturating ensures equivalence with
+          ;; `dl-query` for every stratified program. Pure positive
+          ;; programs skip this and keep the full magic-sets perf win
+          ;; from goal-directed re-derivation.
+          (when
+            (dl-rules-need-presaturation? (dl-rules db))
+            (dl-saturate! db))
+          (let
+            ((query-rel (dl-rel-name query-goal))
+              (query-adn (dl-adorn-goal query-goal)))
+            (let
+              ((query-args (dl-bound-args query-goal query-adn))
+                (rules (dl-rules db)))
+              (let
+                ((rewritten (dl-magic-rewrite rules query-rel query-adn query-args))
+                  (mdb (dl-make-db))
+                  (rule-heads (dl-magic-rule-heads rules)))
+            (do
+              ;; Copy ALL existing facts. EDB-only relations bring their
+              ;; tuples; mixed EDB+IDB relations bring both their EDB
+              ;; portion and any pre-saturated IDB tuples (which the
+              ;; rewritten rules would re-derive anyway). Skipping facts
+              ;; for rule-headed relations would leave the magic run
+              ;; without the EDB portion of mixed relations.
+              (for-each
+                (fn
+                  (rel)
+                  (for-each
+                    (fn (t) (dl-add-fact! mdb t))
+                    (dl-rel-tuples db rel)))
+                (keys (get db :facts)))
+              ;; Seed + rewritten rules.
+              (dl-add-fact! mdb (get rewritten :seed))
+              (for-each (fn (r) (dl-add-rule! mdb r)) (get rewritten :rules))
+              (dl-query mdb query-goal))))))))))

lib/datalog/parser.sx

@@ -0,0 +1,252 @@
+;; lib/datalog/parser.sx — Datalog tokens → AST
+;;
+;; Output shapes:
+;;   Literal (positive)  := (relname arg ... arg)        — SX list
+;;   Literal (negative)  := {:neg (relname arg ... arg)} — dict
+;;   Argument            := var-symbol | atom-symbol | number | string
+;;                        | (op-name arg ... arg)        — arithmetic compound
+;;   Fact                := {:head literal :body ()}
+;;   Rule                := {:head literal :body (lit ... lit)}
+;;   Query               := {:query (lit ... lit)}
+;;   Program             := list of facts / rules / queries
+;;
+;; Variables and constants are both SX symbols; the evaluator dispatches
+;; on first-char case ('A'..'Z' or '_' = variable, otherwise constant).
+;;
+;; The parser permits nested compounds in arg position to support
+;; arithmetic (e.g. (is Z (+ X Y))). Safety analysis at rule-load time
+;; rejects compounds whose head is not an arithmetic operator.
+
+(define
+  dl-pp-peek
+  (fn
+    (st)
+    (let
+      ((i (get st :idx)) (tokens (get st :tokens)))
+      (if (< i (len tokens)) (nth tokens i) {:type "eof" :value nil :pos 0}))))
+
+(define
+  dl-pp-peek2
+  (fn
+    (st)
+    (let
+      ((i (+ (get st :idx) 1)) (tokens (get st :tokens)))
+      (if (< i (len tokens)) (nth tokens i) {:type "eof" :value nil :pos 0}))))
+
+(define
+  dl-pp-advance!
+  (fn (st) (dict-set! st :idx (+ (get st :idx) 1))))
+
+(define
+  dl-pp-at?
+  (fn
+    (st type value)
+    (let
+      ((t (dl-pp-peek st)))
+      (and
+        (= (get t :type) type)
+        (or (= value nil) (= (get t :value) value))))))
+
+(define
+  dl-pp-error
+  (fn
+    (st msg)
+    (let
+      ((t (dl-pp-peek st)))
+      (error
+        (str
+          "Parse error at pos "
+          (get t :pos)
+          ": "
+          msg
+          " (got "
+          (get t :type)
+          " '"
+          (if (= (get t :value) nil) "" (get t :value))
+          "')")))))
+
+(define
+  dl-pp-expect!
+  (fn
+    (st type value)
+    (let
+      ((t (dl-pp-peek st)))
+      (if
+        (dl-pp-at? st type value)
+        (do (dl-pp-advance! st) t)
+        (dl-pp-error
+          st
+          (str "expected " type (if (= value nil) "" (str " '" value "'"))))))))
+
+;; Argument: variable, atom, number, string, or compound (relname/op + parens).
+(define
+  dl-pp-parse-arg
+  (fn
+    (st)
+    (let
+      ((t (dl-pp-peek st)))
+      (let
+        ((ty (get t :type)) (vv (get t :value)))
+        (cond
+          ((= ty "number") (do (dl-pp-advance! st) vv))
+          ((= ty "string") (do (dl-pp-advance! st) vv))
+          ((= ty "var") (do (dl-pp-advance! st) (string->symbol vv)))
+          ;; Negative numeric literal: `-` op directly followed by a
+          ;; number (no `(`) is parsed as a single negative number.
+          ;; This keeps `(-X Y)` (compound) and `-N` (literal) distinct.
+          ((and (= ty "op") (= vv "-")
+                (= (get (dl-pp-peek2 st) :type) "number"))
+            (do
+              (dl-pp-advance! st)
+              (let
+                ((n (get (dl-pp-peek st) :value)))
+                (do (dl-pp-advance! st) (- 0 n)))))
+          ((or (= ty "atom") (= ty "op"))
+            (do
+              (dl-pp-advance! st)
+              (if
+                (dl-pp-at? st "punct" "(")
+                (do
+                  (dl-pp-advance! st)
+                  (let
+                    ((args (dl-pp-parse-arg-list st)))
+                    (do
+                      (dl-pp-expect! st "punct" ")")
+                      (cons (string->symbol vv) args))))
+                (string->symbol vv))))
+          (else (dl-pp-error st "expected term")))))))
+
+;; Comma-separated args inside parens.
+(define
+  dl-pp-parse-arg-list
+  (fn
+    (st)
+    (let
+      ((args (list)))
+      (do
+        (append! args (dl-pp-parse-arg st))
+        (define
+          dl-pp-arg-loop
+          (fn
+            ()
+            (when
+              (dl-pp-at? st "punct" ",")
+              (do
+                (dl-pp-advance! st)
+                (append! args (dl-pp-parse-arg st))
+                (dl-pp-arg-loop)))))
+        (dl-pp-arg-loop)
+        args))))
+
+;; A positive literal: relname (atom or op) followed by optional (args).
+(define
+  dl-pp-parse-positive
+  (fn
+    (st)
+    (let
+      ((t (dl-pp-peek st)))
+      (let
+        ((ty (get t :type)) (vv (get t :value)))
+        (if
+          (or (= ty "atom") (= ty "op"))
+          (do
+            (dl-pp-advance! st)
+            (if
+              (dl-pp-at? st "punct" "(")
+              (do
+                (dl-pp-advance! st)
+                (let
+                  ((args (dl-pp-parse-arg-list st)))
+                  (do
+                    (dl-pp-expect! st "punct" ")")
+                    (cons (string->symbol vv) args))))
+              (list (string->symbol vv))))
+          (dl-pp-error st "expected literal head"))))))
+
+;; A body literal: positive, or not(positive).
+(define
+  dl-pp-parse-body-lit
+  (fn
+    (st)
+    (let
+      ((t1 (dl-pp-peek st)) (t2 (dl-pp-peek2 st)))
+      (if
+        (and
+          (= (get t1 :type) "atom")
+          (= (get t1 :value) "not")
+          (= (get t2 :type) "punct")
+          (= (get t2 :value) "("))
+        (do
+          (dl-pp-advance! st)
+          (dl-pp-advance! st)
+          (let
+            ((inner (dl-pp-parse-positive st)))
+            (do (dl-pp-expect! st "punct" ")") {:neg inner})))
+        (dl-pp-parse-positive st)))))
+
+;; Comma-separated body literals.
+(define
+  dl-pp-parse-body
+  (fn
+    (st)
+    (let
+      ((lits (list)))
+      (do
+        (append! lits (dl-pp-parse-body-lit st))
+        (define
+          dl-pp-body-loop
+          (fn
+            ()
+            (when
+              (dl-pp-at? st "punct" ",")
+              (do
+                (dl-pp-advance! st)
+                (append! lits (dl-pp-parse-body-lit st))
+                (dl-pp-body-loop)))))
+        (dl-pp-body-loop)
+        lits))))
+
+;; Single clause: fact, rule, or query. Consumes trailing dot.
+(define
+  dl-pp-parse-clause
+  (fn
+    (st)
+    (cond
+      ((dl-pp-at? st "op" "?-")
+        (do
+          (dl-pp-advance! st)
+          (let
+            ((body (dl-pp-parse-body st)))
+            (do (dl-pp-expect! st "punct" ".") {:query body}))))
+      (else
+        (let
+          ((head (dl-pp-parse-positive st)))
+          (cond
+            ((dl-pp-at? st "op" ":-")
+              (do
+                (dl-pp-advance! st)
+                (let
+                  ((body (dl-pp-parse-body st)))
+                  (do (dl-pp-expect! st "punct" ".") {:body body :head head}))))
+            (else (do (dl-pp-expect! st "punct" ".") {:body (list) :head head}))))))))
+
+(define
+  dl-parse-program
+  (fn
+    (tokens)
+    (let
+      ((st {:tokens tokens :idx 0}) (clauses (list)))
+      (do
+        (define
+          dl-pp-prog-loop
+          (fn
+            ()
+            (when
+              (not (dl-pp-at? st "eof" nil))
+              (do
+                (append! clauses (dl-pp-parse-clause st))
+                (dl-pp-prog-loop)))))
+        (dl-pp-prog-loop)
+        clauses))))
+
+(define dl-parse (fn (src) (dl-parse-program (dl-tokenize src))))

lib/datalog/scoreboard.json

@@ -0,0 +1,20 @@
+{
+  "lang": "datalog",
+  "total_passed": 276,
+  "total_failed": 0,
+  "total": 276,
+  "suites": [
+    {"name":"tokenize","passed":31,"failed":0,"total":31},
+    {"name":"parse","passed":23,"failed":0,"total":23},
+    {"name":"unify","passed":29,"failed":0,"total":29},
+    {"name":"eval","passed":44,"failed":0,"total":44},
+    {"name":"builtins","passed":26,"failed":0,"total":26},
+    {"name":"semi_naive","passed":8,"failed":0,"total":8},
+    {"name":"negation","passed":12,"failed":0,"total":12},
+    {"name":"aggregates","passed":23,"failed":0,"total":23},
+    {"name":"api","passed":22,"failed":0,"total":22},
+    {"name":"magic","passed":37,"failed":0,"total":37},
+    {"name":"demo","passed":21,"failed":0,"total":21}
+  ],
+  "generated": "2026-05-11T09:40:12+00:00"
+}

lib/datalog/scoreboard.md

@@ -0,0 +1,17 @@
+# datalog scoreboard
+
+**276 / 276 passing** (0 failure(s)).
+
+| Suite | Passed | Total | Status |
+|-------|--------|-------|--------|
+| tokenize | 31 | 31 | ok |
+| parse | 23 | 23 | ok |
+| unify | 29 | 29 | ok |
+| eval | 44 | 44 | ok |
+| builtins | 26 | 26 | ok |
+| semi_naive | 8 | 8 | ok |
+| negation | 12 | 12 | ok |
+| aggregates | 23 | 23 | ok |
+| api | 22 | 22 | ok |
+| magic | 37 | 37 | ok |
+| demo | 21 | 21 | ok |

lib/datalog/strata.sx

@@ -0,0 +1,323 @@
+;; lib/datalog/strata.sx — dependency graph, SCC analysis, stratum assignment.
+;;
+;; A program is stratifiable iff no cycle in its dependency graph passes
+;; through a negative edge. The stratum of relation R is the depth at which
+;; R can first be evaluated:
+;;
+;;   stratum(R) = max over edges (R → S) of:
+;;       stratum(S)         if the edge is positive
+;;       stratum(S) + 1     if the edge is negative
+;;
+;; All relations in the same SCC share a stratum (and the SCC must have only
+;; positive internal edges, else the program is non-stratifiable).
+
+;; Build dep graph: dict {head-rel-name -> ({:rel str :neg bool} ...)}.
+(define
+  dl-build-dep-graph
+  (fn
+    (db)
+    (let ((g {}))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (let
+              ((head-rel (dl-rel-name (get rule :head))))
+              (when
+                (not (nil? head-rel))
+                (do
+                  (when
+                    (not (has-key? g head-rel))
+                    (dict-set! g head-rel (list)))
+                  (let ((existing (get g head-rel)))
+                    (for-each
+                      (fn
+                        (lit)
+                        (cond
+                          ((dl-aggregate? lit)
+                            (let
+                              ((edge (dl-aggregate-dep-edge lit)))
+                              (when
+                                (not (nil? edge))
+                                (append! existing edge))))
+                          (else
+                            (let
+                              ((target
+                                 (cond
+                                   ((and (dict? lit) (has-key? lit :neg))
+                                     (dl-rel-name (get lit :neg)))
+                                   ((dl-builtin? lit) nil)
+                                   ((and (list? lit) (> (len lit) 0))
+                                     (dl-rel-name lit))
+                                   (else nil)))
+                                (neg?
+                                  (and (dict? lit) (has-key? lit :neg))))
+                              (when
+                                (not (nil? target))
+                                (append!
+                                  existing
+                                  {:rel target :neg neg?}))))))
+                      (get rule :body)))))))
+          (dl-rules db))
+        g))))
+
+;; All relations referenced — heads of rules + EDB names + body relations.
+(define
+  dl-all-relations
+  (fn
+    (db)
+    (let ((seen (list)))
+      (do
+        (for-each
+          (fn
+            (k)
+            (when (not (dl-member-string? k seen)) (append! seen k)))
+          (keys (get db :facts)))
+        (for-each
+          (fn
+            (rule)
+            (do
+              (let ((h (dl-rel-name (get rule :head))))
+                (when
+                  (and (not (nil? h)) (not (dl-member-string? h seen)))
+                  (append! seen h)))
+              (for-each
+                (fn
+                  (lit)
+                  (let
+                    ((t
+                       (cond
+                         ((dl-aggregate? lit)
+                           (let ((edge (dl-aggregate-dep-edge lit)))
+                             (if (nil? edge) nil (get edge :rel))))
+                         ((and (dict? lit) (has-key? lit :neg))
+                           (dl-rel-name (get lit :neg)))
+                         ((dl-builtin? lit) nil)
+                         ((and (list? lit) (> (len lit) 0))
+                           (dl-rel-name lit))
+                         (else nil))))
+                    (when
+                      (and (not (nil? t)) (not (dl-member-string? t seen)))
+                      (append! seen t))))
+                (get rule :body))))
+          (dl-rules db))
+        seen))))
+
+;; reach: dict {from: dict {to: edge-info}} where edge-info is
+;;   {:any bool :neg bool}
+;; meaning "any path from `from` to `to`" and "exists a negative-passing
+;; path from `from` to `to`".
+;;
+;; Floyd-Warshall over the dep graph. The 'neg' flag propagates through
+;; concatenation: if any edge along the path is negative, the path's
+;; flag is true.
+(define
+  dl-build-reach
+  (fn
+    (graph nodes)
+    (let ((reach {}))
+      (do
+        (for-each
+          (fn (n) (dict-set! reach n {}))
+          nodes)
+        (for-each
+          (fn
+            (head)
+            (when
+              (has-key? graph head)
+              (for-each
+                (fn
+                  (edge)
+                  (let
+                    ((target (get edge :rel)) (n (get edge :neg)))
+                    (let ((row (get reach head)))
+                      (cond
+                        ((has-key? row target)
+                          (let ((cur (get row target)))
+                            (dict-set!
+                              row
+                              target
+                              {:any true :neg (or n (get cur :neg))})))
+                        (else
+                          (dict-set! row target {:any true :neg n}))))))
+                (get graph head))))
+          nodes)
+        (for-each
+          (fn
+            (k)
+            (for-each
+              (fn
+                (i)
+                (let ((row-i (get reach i)))
+                  (when
+                    (has-key? row-i k)
+                    (let ((ik (get row-i k)) (row-k (get reach k)))
+                      (for-each
+                        (fn
+                          (j)
+                          (when
+                            (has-key? row-k j)
+                            (let ((kj (get row-k j)))
+                              (let
+                                ((combined-neg (or (get ik :neg) (get kj :neg))))
+                                (cond
+                                  ((has-key? row-i j)
+                                    (let ((cur (get row-i j)))
+                                      (dict-set!
+                                        row-i
+                                        j
+                                        {:any true
+                                         :neg (or combined-neg (get cur :neg))})))
+                                  (else
+                                    (dict-set!
+                                      row-i
+                                      j
+                                      {:any true :neg combined-neg})))))))
+                        nodes)))))
+              nodes))
+          nodes)
+        reach))))
+
+;; Returns nil on success, or error message string on failure.
+(define
+  dl-check-stratifiable
+  (fn
+    (db)
+    (let
+      ((graph (dl-build-dep-graph db))
+        (nodes (dl-all-relations db)))
+      (let ((reach (dl-build-reach graph nodes)) (err nil))
+        (do
+          (for-each
+            (fn
+              (rule)
+              (when
+                (nil? err)
+                (let ((head-rel (dl-rel-name (get rule :head))))
+                  (for-each
+                    (fn
+                      (lit)
+                      (cond
+                        ((and (dict? lit) (has-key? lit :neg))
+                          (let ((tgt (dl-rel-name (get lit :neg))))
+                            (when
+                              (and (not (nil? tgt))
+                                   (dl-reach-cycle? reach head-rel tgt))
+                              (set!
+                                err
+                                (str "non-stratifiable: relation " head-rel
+                                     " transitively depends through negation on "
+                                     tgt
+                                     " which depends back on " head-rel)))))
+                        ((dl-aggregate? lit)
+                          (let ((edge (dl-aggregate-dep-edge lit)))
+                            (when
+                              (not (nil? edge))
+                              (let ((tgt (get edge :rel)))
+                                (when
+                                  (and (not (nil? tgt))
+                                       (dl-reach-cycle? reach head-rel tgt))
+                                  (set!
+                                    err
+                                    (str "non-stratifiable: relation "
+                                         head-rel
+                                         " aggregates over " tgt
+                                         " which depends back on "
+                                         head-rel))))))))) 
+                    (get rule :body)))))
+            (dl-rules db))
+          err)))))
+
+(define
+  dl-reach-cycle?
+  (fn
+    (reach a b)
+    (and
+      (dl-reach-row-has? reach b a)
+      (dl-reach-row-has? reach a b))))
+
+(define
+  dl-reach-row-has?
+  (fn
+    (reach from to)
+    (let ((row (get reach from)))
+      (and (not (nil? row)) (has-key? row to)))))
+
+;; Compute stratum per relation. Iteratively propagate from EDB roots.
+;; Uses the per-relation max-stratum-of-deps formula. Stops when stable.
+(define
+  dl-compute-strata
+  (fn
+    (db)
+    (let
+      ((graph (dl-build-dep-graph db))
+        (nodes (dl-all-relations db))
+        (strata {}))
+      (do
+        (for-each (fn (n) (dict-set! strata n 0)) nodes)
+        (let ((changed true))
+          (do
+            (define
+              dl-cs-loop
+              (fn
+                ()
+                (when
+                  changed
+                  (do
+                    (set! changed false)
+                    (for-each
+                      (fn
+                        (head)
+                        (when
+                          (has-key? graph head)
+                          (for-each
+                            (fn
+                              (edge)
+                              (let
+                                ((tgt (get edge :rel))
+                                  (n (get edge :neg)))
+                                (let
+                                  ((tgt-strat
+                                     (if (has-key? strata tgt)
+                                       (get strata tgt) 0))
+                                    (cur (get strata head)))
+                                  (let
+                                    ((needed
+                                       (if n (+ tgt-strat 1) tgt-strat)))
+                                    (when
+                                      (> needed cur)
+                                      (do
+                                        (dict-set! strata head needed)
+                                        (set! changed true)))))))
+                            (get graph head))))
+                      nodes)
+                    (dl-cs-loop)))))
+            (dl-cs-loop)))
+        strata))))
+
+;; Group rules by their head's stratum. Returns dict {stratum-int -> rules}.
+(define
+  dl-group-rules-by-stratum
+  (fn
+    (db strata)
+    (let ((groups {}) (max-s 0))
+      (do
+        (for-each
+          (fn
+            (rule)
+            (let
+              ((head-rel (dl-rel-name (get rule :head))))
+              (let
+                ((s (if (has-key? strata head-rel)
+                       (get strata head-rel) 0)))
+                (do
+                  (when (> s max-s) (set! max-s s))
+                  (let
+                    ((sk (str s)))
+                    (do
+                      (when
+                        (not (has-key? groups sk))
+                        (dict-set! groups sk (list)))
+                      (append! (get groups sk) rule)))))))
+          (dl-rules db))
+        {:groups groups :max max-s}))))

lib/datalog/tests/aggregates.sx

@@ -0,0 +1,357 @@
+;; lib/datalog/tests/aggregates.sx — count / sum / min / max.
+
+(define dl-at-pass 0)
+(define dl-at-fail 0)
+(define dl-at-failures (list))
+
+(define
+  dl-at-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-at-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-at-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-at-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-at-deep=? (nth a i) (nth b i))) false)
+      (else (dl-at-deq-l? a b (+ i 1))))))
+
+(define
+  dl-at-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-at-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-at-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-at-set=?
+  (fn
+    (a b)
+    (and
+      (= (len a) (len b))
+      (dl-at-subset? a b)
+      (dl-at-subset? b a))))
+
+(define
+  dl-at-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-at-contains? ys (first xs))) false)
+      (else (dl-at-subset? (rest xs) ys)))))
+
+(define
+  dl-at-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-at-deep=? (first xs) target) true)
+      (else (dl-at-contains? (rest xs) target)))))
+
+(define
+  dl-at-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-at-deep=? got expected)
+      (set! dl-at-pass (+ dl-at-pass 1))
+      (do
+        (set! dl-at-fail (+ dl-at-fail 1))
+        (append!
+          dl-at-failures
+          (str
+            name
+            "\n    expected: " expected
+            "\n    got:      " got))))))
+
+(define
+  dl-at-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-at-set=? got expected)
+      (set! dl-at-pass (+ dl-at-pass 1))
+      (do
+        (set! dl-at-fail (+ dl-at-fail 1))
+        (append!
+          dl-at-failures
+          (str
+            name
+            "\n    expected (set): " expected
+            "\n    got:            " got))))))
+
+(define
+  dl-at-throws?
+  (fn
+    (thunk)
+    (let
+      ((threw false))
+      (do
+        (guard
+          (e (#t (set! threw true)))
+          (thunk))
+        threw))))
+
+(define
+  dl-at-run-all!
+  (fn
+    ()
+    (do
+      ;; count
+      (dl-at-test-set! "count siblings"
+        (dl-query
+          (dl-program
+            "parent(p, bob). parent(p, alice). parent(p, charlie).
+             sibling(X, Y) :- parent(P, X), parent(P, Y), !=(X, Y).
+             sib_count(N) :- count(N, S, sibling(bob, S)).")
+          (list (quote sib_count) (quote N)))
+        (list {:N 2}))
+
+      ;; sum
+      (dl-at-test-set! "sum prices"
+        (dl-query
+          (dl-program
+            "price(apple, 5). price(pear, 7). price(plum, 3).
+             total(T) :- sum(T, X, price(F, X)).")
+          (list (quote total) (quote T)))
+        (list {:T 15}))
+
+      ;; min
+      (dl-at-test-set! "min score"
+        (dl-query
+          (dl-program
+            "score(alice, 80). score(bob, 65). score(carol, 92).
+             lo(M) :- min(M, S, score(P, S)).")
+          (list (quote lo) (quote M)))
+        (list {:M 65}))
+
+      ;; max
+      (dl-at-test-set! "max score"
+        (dl-query
+          (dl-program
+            "score(alice, 80). score(bob, 65). score(carol, 92).
+             hi(M) :- max(M, S, score(P, S)).")
+          (list (quote hi) (quote M)))
+        (list {:M 92}))
+
+      ;; count over derived relation (stratification needed).
+      (dl-at-test-set! "count over derived"
+        (dl-query
+          (dl-program
+            "parent(a, b). parent(a, c). parent(b, d). parent(c, e).
+             ancestor(X, Y) :- parent(X, Y).
+             ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).
+             num_ancestors(N) :- count(N, X, ancestor(a, X)).")
+          (list (quote num_ancestors) (quote N)))
+        (list {:N 4}))
+
+      ;; count with no matches → 0.
+      (dl-at-test-set! "count empty"
+        (dl-query
+          (dl-program
+            "p(1). p(2).
+             zero(N) :- count(N, X, q(X)).")
+          (list (quote zero) (quote N)))
+        (list {:N 0}))
+
+      ;; sum with no matches → 0.
+      (dl-at-test-set! "sum empty"
+        (dl-query
+          (dl-program
+            "p(1). p(2).
+             total(T) :- sum(T, X, q(X)).")
+          (list (quote total) (quote T)))
+        (list {:T 0}))
+
+      ;; min with no matches → rule does not fire.
+      (dl-at-test-set! "min empty"
+        (dl-query
+          (dl-program
+            "p(1). p(2).
+             lo(M) :- min(M, X, q(X)).")
+          (list (quote lo) (quote M)))
+        (list))
+
+      ;; Aggregate with comparison filter on result.
+      (dl-at-test-set! "popularity threshold"
+        (dl-query
+          (dl-program
+            "post(p1). post(p2).
+             liked(u1, p1). liked(u2, p1). liked(u3, p1).
+             liked(u1, p2). liked(u2, p2).
+             popular(P) :- post(P), count(N, U, liked(U, P)), >=(N, 3).")
+          (list (quote popular) (quote P)))
+        (list {:P (quote p1)}))
+
+      ;; findall: collect distinct values into a list.
+      (dl-at-test-set! "findall over EDB"
+        (dl-query
+          (dl-program
+            "p(a). p(b). p(c).
+             all_p(L) :- findall(L, X, p(X)).")
+          (list (quote all_p) (quote L)))
+        (list {:L (list (quote a) (quote b) (quote c))}))
+
+      (dl-at-test-set! "findall over derived"
+        (dl-query
+          (dl-program
+            "parent(a, b). parent(b, c). parent(c, d).
+             ancestor(X, Y) :- parent(X, Y).
+             ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).
+             desc(L) :- findall(L, X, ancestor(a, X)).")
+          (list (quote desc) (quote L)))
+        (list {:L (list (quote b) (quote c) (quote d))}))
+
+      (dl-at-test-set! "findall empty"
+        (dl-query
+          (dl-program
+            "p(1).
+             all_q(L) :- findall(L, X, q(X)).")
+          (list (quote all_q) (quote L)))
+        (list {:L (list)}))
+
+      ;; Aggregate vs single distinct.
+      ;; Group-by via aggregate-in-rule-body. Per-user friend count
+      ;; over a friends relation. The U var is bound by the prior
+      ;; positive lit u(U) so the aggregate counts only U-rooted
+      ;; friends per group.
+      (dl-at-test-set! "group-by per-user friend count"
+        (dl-query
+          (dl-program
+            "u(alice). u(bob). u(carol).
+             f(alice, x). f(alice, y). f(bob, x).
+             counts(U, N) :- u(U), count(N, X, f(U, X)).")
+          (list (quote counts) (quote U) (quote N)))
+        (list
+          {:U (quote alice) :N 2}
+          {:U (quote bob) :N 1}
+          {:U (quote carol) :N 0}))
+
+      ;; Stratification: recursion through aggregation is rejected.
+      ;; Aggregate validates that second arg is a variable.
+      (dl-at-test! "agg second arg must be var"
+        (dl-at-throws?
+          (fn () (dl-eval "p(1). q(N) :- count(N, 5, p(X))." "?- q(N).")))
+        true)
+
+      ;; Aggregate validates that third arg is a positive literal.
+      (dl-at-test! "agg third arg must be a literal"
+        (dl-at-throws?
+          (fn () (dl-eval "p(1). q(N) :- count(N, X, 42)." "?- q(N).")))
+        true)
+
+      ;; Aggregate validates that the agg-var (2nd arg) appears in the
+      ;; goal. Without it every match contributes the same unbound
+      ;; symbol — count silently returns 1, sum raises a confusing
+      ;; "expected number" error, etc. Catch the mistake at safety
+      ;; check time instead.
+      (dl-at-test! "agg-var must appear in goal"
+        (dl-at-throws?
+          (fn ()
+            (dl-eval
+              "p(1). p(2). c(N) :- count(N, Y, p(X))."
+              "?- c(N).")))
+        true)
+
+      ;; Indirect recursion through aggregation also rejected.
+      ;; q -> r (via positive lit), r -> q (via aggregate body).
+      ;; The aggregate edge counts as negation for stratification.
+      (dl-at-test! "indirect agg cycle rejected"
+        (dl-at-throws?
+          (fn ()
+            (let ((db (dl-make-db)))
+              (do
+                (dl-add-rule! db
+                  {:head (list (quote q) (quote N))
+                   :body (list (list (quote r) (quote N)))})
+                (dl-add-rule! db
+                  {:head (list (quote r) (quote N))
+                   :body (list (list (quote count) (quote N) (quote X)
+                                     (list (quote q) (quote X))))})
+                (dl-saturate! db)))))
+        true)
+
+      (dl-at-test! "agg recursion rejected"
+        (dl-at-throws?
+          (fn ()
+            (let ((db (dl-make-db)))
+              (do
+                (dl-add-rule! db
+                  {:head (list (quote q) (quote N))
+                   :body (list (list (quote count) (quote N) (quote X)
+                                     (list (quote q) (quote X))))})
+                (dl-saturate! db)))))
+        true)
+
+      ;; Negation + aggregation in the same body — different strata.
+      (dl-at-test-set! "neg + agg coexist"
+        (dl-query
+          (dl-program
+            "u(a). u(b). u(c). banned(b).
+             active(X) :- u(X), not(banned(X)).
+             cnt(N) :- count(N, X, active(X)).")
+          (list (quote cnt) (quote N)))
+        (list {:N 2}))
+
+      ;; Min over a derived empty relation: no result.
+      (dl-at-test-set! "min over empty derived"
+        (dl-query
+          (dl-program
+            "s(50). s(60).
+             score(N) :- s(N), >(N, 100).
+             low(M) :- min(M, X, score(X)).")
+          (list (quote low) (quote M)))
+        (list))
+
+      ;; Aggregates as the top-level query goal (regression for
+      ;; dl-match-lit aggregate dispatch and projection cleanup).
+      (dl-at-test-set! "count as query goal"
+        (dl-query
+          (dl-program "p(1). p(2). p(3). p(4).")
+          (list (quote count) (quote N) (quote X) (list (quote p) (quote X))))
+        (list {:N 4}))
+
+      (dl-at-test-set! "findall as query goal"
+        (dl-query
+          (dl-program "p(1). p(2). p(3).")
+          (list (quote findall) (quote L) (quote X)
+                (list (quote p) (quote X))))
+        (list {:L (list 1 2 3)}))
+
+      (dl-at-test-set! "distinct counted once"
+        (dl-query
+          (dl-program
+            "rated(alice, x). rated(alice, y). rated(bob, x).
+             rater_count(N) :- count(N, U, rated(U, F)).")
+          (list (quote rater_count) (quote N)))
+        (list {:N 2})))))
+
+(define
+  dl-aggregates-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-at-pass 0)
+      (set! dl-at-fail 0)
+      (set! dl-at-failures (list))
+      (dl-at-run-all!)
+      {:passed dl-at-pass
+       :failed dl-at-fail
+       :total (+ dl-at-pass dl-at-fail)
+       :failures dl-at-failures})))

lib/datalog/tests/api.sx

@@ -0,0 +1,350 @@
+;; lib/datalog/tests/api.sx — SX-data embedding API.
+
+(define dl-api-pass 0)
+(define dl-api-fail 0)
+(define dl-api-failures (list))
+
+(define
+  dl-api-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-api-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-api-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-api-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-api-deep=? (nth a i) (nth b i))) false)
+      (else (dl-api-deq-l? a b (+ i 1))))))
+
+(define
+  dl-api-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-api-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-api-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-api-set=?
+  (fn
+    (a b)
+    (and
+      (= (len a) (len b))
+      (dl-api-subset? a b)
+      (dl-api-subset? b a))))
+
+(define
+  dl-api-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-api-contains? ys (first xs))) false)
+      (else (dl-api-subset? (rest xs) ys)))))
+
+(define
+  dl-api-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-api-deep=? (first xs) target) true)
+      (else (dl-api-contains? (rest xs) target)))))
+
+(define
+  dl-api-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-api-deep=? got expected)
+      (set! dl-api-pass (+ dl-api-pass 1))
+      (do
+        (set! dl-api-fail (+ dl-api-fail 1))
+        (append!
+          dl-api-failures
+          (str
+            name
+            "\n    expected: " expected
+            "\n    got:      " got))))))
+
+(define
+  dl-api-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-api-set=? got expected)
+      (set! dl-api-pass (+ dl-api-pass 1))
+      (do
+        (set! dl-api-fail (+ dl-api-fail 1))
+        (append!
+          dl-api-failures
+          (str
+            name
+            "\n    expected (set): " expected
+            "\n    got:            " got))))))
+
+(define
+  dl-api-run-all!
+  (fn
+    ()
+    (do
+      ;; dl-program-data with arrow form.
+      (dl-api-test-set! "data API ancestor closure"
+        (dl-query
+          (dl-program-data
+            (quote ((parent tom bob) (parent bob ann) (parent ann pat)))
+            (quote
+              ((ancestor X Y <- (parent X Y))
+               (ancestor X Z <- (parent X Y) (ancestor Y Z)))))
+          (quote (ancestor tom X)))
+        (list {:X (quote bob)} {:X (quote ann)} {:X (quote pat)}))
+
+      ;; dl-program-data with dict rules.
+      (dl-api-test-set! "data API with dict rules"
+        (dl-query
+          (dl-program-data
+            (quote ((p a) (p b) (p c)))
+            (list
+              {:head (quote (q X)) :body (quote ((p X)))}))
+          (quote (q X)))
+        (list {:X (quote a)} {:X (quote b)} {:X (quote c)}))
+
+      ;; dl-rule helper.
+      (dl-api-test-set! "dl-rule constructor"
+        (dl-query
+          (dl-program-data
+            (quote ((p 1) (p 2)))
+            (list (dl-rule (quote (q X)) (quote ((p X))))))
+          (quote (q X)))
+        (list {:X 1} {:X 2}))
+
+      ;; dl-assert! adds and re-derives.
+      (dl-api-test-set! "dl-assert! incremental"
+        (let
+          ((db (dl-program-data
+                 (quote ((parent tom bob) (parent bob ann)))
+                 (quote
+                   ((ancestor X Y <- (parent X Y))
+                    (ancestor X Z <- (parent X Y) (ancestor Y Z)))))))
+          (do
+            (dl-saturate! db)
+            (dl-assert! db (quote (parent ann pat)))
+            (dl-query db (quote (ancestor tom X)))))
+        (list {:X (quote bob)} {:X (quote ann)} {:X (quote pat)}))
+
+      ;; dl-retract! removes a fact and recomputes IDB.
+      (dl-api-test-set! "dl-retract! removes derived"
+        (let
+          ((db (dl-program-data
+                 (quote ((parent tom bob) (parent bob ann) (parent ann pat)))
+                 (quote
+                   ((ancestor X Y <- (parent X Y))
+                    (ancestor X Z <- (parent X Y) (ancestor Y Z)))))))
+          (do
+            (dl-saturate! db)
+            (dl-retract! db (quote (parent bob ann)))
+            (dl-query db (quote (ancestor tom X)))))
+        (list {:X (quote bob)}))
+
+      ;; dl-retract! on a relation with BOTH explicit facts AND a rule
+      ;; (a "mixed" relation) used to wipe the EDB portion when the IDB
+      ;; was re-derived, even when the retract didn't match anything.
+      ;; :edb-keys provenance now preserves user-asserted facts.
+      (dl-api-test-set! "dl-retract! preserves EDB in mixed relation"
+        (let
+          ((db (dl-program-data
+                 (quote ((p a) (p b) (q c)))
+                 (quote ((p X <- (q X)))))))
+          (do
+            (dl-saturate! db)
+            ;; Retract a non-existent tuple — should be a no-op.
+            (dl-retract! db (quote (p z)))
+            (dl-query db (quote (p X)))))
+        (list {:X (quote a)} {:X (quote b)} {:X (quote c)}))
+
+      ;; And retracting an actual EDB fact in a mixed relation drops
+      ;; only that fact; the derived portion stays.
+      (dl-api-test-set! "dl-retract! mixed: drop EDB, keep IDB"
+        (let
+          ((db (dl-program-data
+                 (quote ((p a) (p b) (q c)))
+                 (quote ((p X <- (q X)))))))
+          (do
+            (dl-saturate! db)
+            (dl-retract! db (quote (p a)))
+            (dl-query db (quote (p X)))))
+        (list {:X (quote b)} {:X (quote c)}))
+
+      ;; dl-program-data + dl-query with constants in head.
+      (dl-api-test-set! "constant-in-head data"
+        (dl-query
+          (dl-program-data
+            (quote ((edge a b) (edge b c) (edge c a)))
+            (quote
+              ((reach X Y <- (edge X Y))
+               (reach X Z <- (edge X Y) (reach Y Z)))))
+          (quote (reach a X)))
+        (list {:X (quote a)} {:X (quote b)} {:X (quote c)}))
+
+      ;; Assert into empty db.
+      (dl-api-test-set! "assert into empty"
+        (let
+          ((db (dl-program-data (list) (list))))
+          (do
+            (dl-assert! db (quote (p 1)))
+            (dl-assert! db (quote (p 2)))
+            (dl-query db (quote (p X)))))
+        (list {:X 1} {:X 2}))
+
+      ;; Multi-goal query: pass list of literals.
+      (dl-api-test-set! "multi-goal query"
+        (dl-query
+          (dl-program-data
+            (quote ((p 1) (p 2) (p 3) (q 2) (q 3)))
+            (list))
+          (list (quote (p X)) (quote (q X))))
+        (list {:X 2} {:X 3}))
+
+      ;; Multi-goal with comparison.
+      (dl-api-test-set! "multi-goal with comparison"
+        (dl-query
+          (dl-program-data
+            (quote ((n 1) (n 2) (n 3) (n 4) (n 5)))
+            (list))
+          (list (quote (n X)) (list (string->symbol ">") (quote X) 2)))
+        (list {:X 3} {:X 4} {:X 5}))
+
+      ;; dl-eval: single-call source + query.
+      (dl-api-test-set! "dl-eval ancestor"
+        (dl-eval
+          "parent(a, b). parent(b, c).
+           ancestor(X, Y) :- parent(X, Y).
+           ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z)."
+          "?- ancestor(a, X).")
+        (list {:X (quote b)} {:X (quote c)}))
+
+      (dl-api-test-set! "dl-eval multi-goal"
+        (dl-eval
+          "p(1). p(2). p(3). q(2). q(3)."
+          "?- p(X), q(X).")
+        (list {:X 2} {:X 3}))
+
+      ;; dl-rules-of: rules with head matching a relation name.
+      (dl-api-test! "dl-rules-of count"
+        (let
+          ((db (dl-program
+                 "p(1). q(X) :- p(X). r(X) :- p(X). q(2).")))
+          (len (dl-rules-of db "q")))
+        1)
+
+      (dl-api-test! "dl-rules-of empty"
+        (let
+          ((db (dl-program "p(1). p(2).")))
+          (len (dl-rules-of db "q")))
+        0)
+
+      ;; dl-clear-idb!: wipe rule-headed relations.
+      (dl-api-test! "dl-clear-idb! wipes IDB"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (do
+            (dl-saturate! db)
+            (dl-clear-idb! db)
+            (len (dl-relation db "ancestor"))))
+        0)
+
+      (dl-api-test! "dl-clear-idb! preserves EDB"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c).
+                  ancestor(X, Y) :- parent(X, Y).")))
+          (do
+            (dl-saturate! db)
+            (dl-clear-idb! db)
+            (len (dl-relation db "parent"))))
+        2)
+
+      ;; dl-eval-magic — routes single-goal queries through
+      ;; magic-sets evaluation.
+      (dl-api-test-set! "dl-eval-magic ancestor"
+        (dl-eval-magic
+          "parent(a, b). parent(b, c).
+           ancestor(X, Y) :- parent(X, Y).
+           ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z)."
+          "?- ancestor(a, X).")
+        (list {:X (quote b)} {:X (quote c)}))
+
+      ;; Equivalence: dl-eval and dl-eval-magic produce the same
+      ;; answers for any well-formed query (magic-sets is a perf
+      ;; alternative, not a semantic change).
+      (dl-api-test! "dl-eval ≡ dl-eval-magic on ancestor"
+        (let
+          ((source "parent(a, b). parent(b, c). parent(c, d).
+                    ancestor(X, Y) :- parent(X, Y).
+                    ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z)."))
+          (let
+            ((semi (dl-eval source "?- ancestor(a, X)."))
+              (magic (dl-eval-magic source "?- ancestor(a, X).")))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Comprehensive integration: recursion + stratified negation
+      ;; + aggregation + comparison composed in a single program.
+      ;; (Uses _Anything as a regular var instead of `_` so the
+      ;;  outer rule binds via the reach lit.)
+      (dl-api-test-set! "integration"
+        (dl-eval
+          (str
+            "edge(a, b). edge(b, c). edge(c, d). edge(a, d). "
+            "banned(c). "
+            "reach(X, Y) :- edge(X, Y). "
+            "reach(X, Z) :- edge(X, Y), reach(Y, Z). "
+            "safe(X, Y) :- reach(X, Y), not(banned(Y)). "
+            "reach_count(X, N) :- reach(X, Z), count(N, Y, safe(X, Y)). "
+            "popular(X) :- reach_count(X, N), >=(N, 2).")
+          "?- popular(X).")
+        (list {:X (quote a)}))
+
+      ;; dl-rule-from-list with no arrow → fact-style.
+      (dl-api-test-set! "no arrow → fact-like rule"
+        (let
+          ((rule (dl-rule-from-list (quote (foo X Y)))))
+          (list rule))
+        (list {:head (quote (foo X Y)) :body (list)}))
+
+      ;; dl-coerce-rule on dict passes through.
+      (dl-api-test-set! "coerce dict rule"
+        (let
+          ((d {:head (quote (h X)) :body (quote ((b X)))}))
+          (list (dl-coerce-rule d)))
+        (list {:head (quote (h X)) :body (quote ((b X)))})))))
+
+(define
+  dl-api-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-api-pass 0)
+      (set! dl-api-fail 0)
+      (set! dl-api-failures (list))
+      (dl-api-run-all!)
+      {:passed dl-api-pass
+       :failed dl-api-fail
+       :total (+ dl-api-pass dl-api-fail)
+       :failures dl-api-failures})))

lib/datalog/tests/builtins.sx

@@ -0,0 +1,285 @@
+;; lib/datalog/tests/builtins.sx — comparison + arithmetic body literals.
+
+(define dl-bt-pass 0)
+(define dl-bt-fail 0)
+(define dl-bt-failures (list))
+
+(define
+  dl-bt-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-bt-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let
+          ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-bt-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-bt-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-bt-deep=? (nth a i) (nth b i))) false)
+      (else (dl-bt-deq-l? a b (+ i 1))))))
+
+(define
+  dl-bt-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i))) (not (dl-bt-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-bt-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-bt-set=?
+  (fn
+    (a b)
+    (and (= (len a) (len b)) (dl-bt-subset? a b) (dl-bt-subset? b a))))
+
+(define
+  dl-bt-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-bt-contains? ys (first xs))) false)
+      (else (dl-bt-subset? (rest xs) ys)))))
+
+(define
+  dl-bt-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-bt-deep=? (first xs) target) true)
+      (else (dl-bt-contains? (rest xs) target)))))
+
+(define
+  dl-bt-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-bt-set=? got expected)
+      (set! dl-bt-pass (+ dl-bt-pass 1))
+      (do
+        (set! dl-bt-fail (+ dl-bt-fail 1))
+        (append!
+          dl-bt-failures
+          (str
+            name
+            "\n    expected (set): "
+            expected
+            "\n    got:            "
+            got))))))
+
+(define
+  dl-bt-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-bt-deep=? got expected)
+      (set! dl-bt-pass (+ dl-bt-pass 1))
+      (do
+        (set! dl-bt-fail (+ dl-bt-fail 1))
+        (append!
+          dl-bt-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define
+  dl-bt-throws?
+  (fn
+    (thunk)
+    (let
+      ((threw false))
+      (do (guard (e (#t (set! threw true))) (thunk)) threw))))
+
+(define
+  dl-bt-run-all!
+  (fn
+    ()
+    (do
+      (dl-bt-test-set!
+        "less than filter"
+        (dl-query
+          (dl-program
+            "age(alice, 30). age(bob, 17). age(carol, 22).\n             adult(X) :- age(X, A), >=(A, 18).")
+          (list (quote adult) (quote X)))
+        (list {:X (quote alice)} {:X (quote carol)}))
+      (dl-bt-test-set!
+        "less-equal filter"
+        (dl-query
+          (dl-program
+            "n(1). n(2). n(3). n(4). n(5).\n             small(X) :- n(X), <=(X, 3).")
+          (list (quote small) (quote X)))
+        (list {:X 1} {:X 2} {:X 3}))
+      (dl-bt-test-set!
+        "not-equal filter"
+        (dl-query
+          (dl-program
+            "p(1, 2). p(2, 2). p(3, 4).\n             diff(X, Y) :- p(X, Y), !=(X, Y).")
+          (list (quote diff) (quote X) (quote Y)))
+        (list {:X 1 :Y 2} {:X 3 :Y 4}))
+      (dl-bt-test-set!
+        "is plus"
+        (dl-query
+          (dl-program
+            "n(1). n(2). n(3).\n             succ(X, Y) :- n(X), is(Y, +(X, 1)).")
+          (list (quote succ) (quote X) (quote Y)))
+        (list {:X 1 :Y 2} {:X 2 :Y 3} {:X 3 :Y 4}))
+      (dl-bt-test-set!
+        "is multiply"
+        (dl-query
+          (dl-program
+            "n(2). n(3). n(4).\n             square(X, Y) :- n(X), is(Y, *(X, X)).")
+          (list (quote square) (quote X) (quote Y)))
+        (list {:X 2 :Y 4} {:X 3 :Y 9} {:X 4 :Y 16}))
+      (dl-bt-test-set!
+        "is nested expr"
+        (dl-query
+          (dl-program
+            "n(1). n(2). n(3).\n             f(X, Y) :- n(X), is(Y, *(+(X, 1), 2)).")
+          (list (quote f) (quote X) (quote Y)))
+        (list {:X 1 :Y 4} {:X 2 :Y 6} {:X 3 :Y 8}))
+      (dl-bt-test-set!
+        "is bound LHS — equality"
+        (dl-query
+          (dl-program
+            "n(1, 2). n(2, 5). n(3, 4).\n             succ(X, Y) :- n(X, Y), is(Y, +(X, 1)).")
+          (list (quote succ) (quote X) (quote Y)))
+        (list {:X 1 :Y 2} {:X 3 :Y 4}))
+      (dl-bt-test-set!
+        "triple via is"
+        (dl-query
+          (dl-program
+            "n(1). n(2). n(3).\n             triple(X, Y) :- n(X), is(Y, *(X, 3)).")
+          (list (quote triple) (quote X) (quote Y)))
+        (list {:X 1 :Y 3} {:X 2 :Y 6} {:X 3 :Y 9}))
+      (dl-bt-test-set!
+        "= unifies var with constant"
+        (dl-query
+          (dl-program "p(a). p(b).\n             qual(X) :- p(X), =(X, a).")
+          (list (quote qual) (quote X)))
+        (list {:X (quote a)}))
+      (dl-bt-test-set!
+        "= unifies two vars (one bound)"
+        (dl-query
+          (dl-program "p(a). p(b).\n             twin(X, Y) :- p(X), =(Y, X).")
+          (list (quote twin) (quote X) (quote Y)))
+        (list {:X (quote a) :Y (quote a)} {:X (quote b) :Y (quote b)}))
+      (dl-bt-test!
+        "big count"
+        (let
+          ((db (dl-program "n(0). n(1). n(2). n(3). n(4). n(5). n(6). n(7). n(8). n(9).\n                  big(X) :- n(X), >=(X, 5).")))
+          (do (dl-saturate! db) (len (dl-relation db "big"))))
+        5)
+      ;; Built-in / arithmetic literals work as standalone query goals
+      ;; (without needing a wrapper rule).
+      (dl-bt-test-set! "comparison-only goal true"
+        (dl-eval "" "?- <(1, 2).")
+        (list {}))
+
+      (dl-bt-test-set! "comparison-only goal false"
+        (dl-eval "" "?- <(2, 1).")
+        (list))
+
+      (dl-bt-test-set! "is goal binds"
+        (dl-eval "" "?- is(N, +(2, 3)).")
+        (list {:N 5}))
+
+      ;; Bounded successor: a recursive rule with a comparison
+      ;; guard terminates because the Herbrand base is effectively
+      ;; bounded.
+      (dl-bt-test-set! "bounded successor"
+        (dl-query
+          (dl-program
+            "nat(0).
+             nat(Y) :- nat(X), is(Y, +(X, 1)), <(Y, 5).")
+          (list (quote nat) (quote X)))
+        (list {:X 0} {:X 1} {:X 2} {:X 3} {:X 4}))
+
+      (dl-bt-test!
+        "unsafe — comparison without binder"
+        (dl-bt-throws? (fn () (dl-program "p(X) :- <(X, 5).")))
+        true)
+      (dl-bt-test!
+        "unsafe — comparison both unbound"
+        (dl-bt-throws? (fn () (dl-program "p(X, Y) :- <(X, Y), q(X).")))
+        true)
+      (dl-bt-test!
+        "unsafe — is uses unbound RHS var"
+        (dl-bt-throws?
+          (fn () (dl-program "p(X, Y) :- q(X), is(Y, +(X, Z)).")))
+        true)
+      (dl-bt-test!
+        "unsafe — is on its own"
+        (dl-bt-throws? (fn () (dl-program "p(Y) :- is(Y, +(X, 1)).")))
+        true)
+      (dl-bt-test!
+        "unsafe — = between two unbound"
+        (dl-bt-throws? (fn () (dl-program "p(X, Y) :- =(X, Y).")))
+        true)
+      (dl-bt-test!
+        "safe — is binds head var"
+        (dl-bt-throws?
+          (fn () (dl-program "n(1). p(Y) :- n(X), is(Y, +(X, 1)).")))
+        false)
+      (dl-bt-test!
+        "safe — comparison after binder"
+        (dl-bt-throws?
+          (fn () (dl-program "n(1). big(X) :- n(X), >=(X, 0).")))
+        false)
+      (dl-bt-test!
+        "safe — = binds head var"
+        (dl-bt-throws?
+          (fn () (dl-program "p(a). p(b). x(Y) :- p(X), =(Y, X).")))
+        false)
+
+      ;; Division by zero raises with a clear error. Without this guard
+      ;; SX's `/` returned IEEE infinity, which then silently flowed
+      ;; through comparisons and aggregations.
+      (dl-bt-test!
+        "is — division by zero raises"
+        (dl-bt-throws?
+          (fn ()
+            (dl-eval "p(10). q(R) :- p(X), is(R, /(X, 0))." "?- q(R).")))
+        true)
+
+      ;; Comparison ops `<`, `<=`, `>`, `>=` require both operands to
+      ;; have the same primitive type. Cross-type comparisons used to
+      ;; silently return false (for some pairs) or raise a confusing
+      ;; host-level error (for others) — now they all raise with a
+      ;; message that names the offending values.
+      (dl-bt-test!
+        "comparison — string vs number raises"
+        (dl-bt-throws?
+          (fn ()
+            (dl-eval "p(\"hello\"). q(X) :- p(X), <(X, 5)." "?- q(X).")))
+        true)
+
+      ;; `!=` is the exception — it's a polymorphic inequality test
+      ;; (uses dl-tuple-equal? underneath) so cross-type pairs are
+      ;; legitimate (and trivially unequal).
+      (dl-bt-test-set! "!= works across types"
+        (dl-query
+          (dl-program
+            "p(1). p(\"1\"). q(X) :- p(X), !=(X, 1).")
+          (quote (q X)))
+        (list {:X "1"})))))
+
+(define
+  dl-builtins-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-bt-pass 0)
+      (set! dl-bt-fail 0)
+      (set! dl-bt-failures (list))
+      (dl-bt-run-all!)
+      {:failures dl-bt-failures :total (+ dl-bt-pass dl-bt-fail) :passed dl-bt-pass :failed dl-bt-fail})))

lib/datalog/tests/demo.sx

@@ -0,0 +1,321 @@
+;; lib/datalog/tests/demo.sx — Phase 10 demo programs.
+
+(define dl-demo-pass 0)
+(define dl-demo-fail 0)
+(define dl-demo-failures (list))
+
+(define
+  dl-demo-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-demo-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-demo-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-demo-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-demo-deep=? (nth a i) (nth b i))) false)
+      (else (dl-demo-deq-l? a b (+ i 1))))))
+
+(define
+  dl-demo-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-demo-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-demo-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-demo-set=?
+  (fn
+    (a b)
+    (and
+      (= (len a) (len b))
+      (dl-demo-subset? a b)
+      (dl-demo-subset? b a))))
+
+(define
+  dl-demo-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-demo-contains? ys (first xs))) false)
+      (else (dl-demo-subset? (rest xs) ys)))))
+
+(define
+  dl-demo-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-demo-deep=? (first xs) target) true)
+      (else (dl-demo-contains? (rest xs) target)))))
+
+(define
+  dl-demo-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-demo-set=? got expected)
+      (set! dl-demo-pass (+ dl-demo-pass 1))
+      (do
+        (set! dl-demo-fail (+ dl-demo-fail 1))
+        (append!
+          dl-demo-failures
+          (str
+            name
+            "\n    expected (set): " expected
+            "\n    got:            " got))))))
+
+(define
+  dl-demo-run-all!
+  (fn
+    ()
+    (do
+      ;; ── Federation ──────────────────────────────────────────
+      (dl-demo-test-set! "mutuals"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob alice)
+                    (follows bob carol) (follows carol dave)))
+            dl-demo-federation-rules)
+          (quote (mutual alice X)))
+        (list {:X (quote bob)}))
+
+      (dl-demo-test-set! "reachable transitive"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob carol) (follows carol dave)))
+            dl-demo-federation-rules)
+          (quote (reachable alice X)))
+        (list {:X (quote bob)} {:X (quote carol)} {:X (quote dave)}))
+
+      (dl-demo-test-set! "foaf"
+        (dl-query
+          (dl-demo-make
+            (quote ((follows alice bob) (follows bob carol) (follows alice dave)))
+            dl-demo-federation-rules)
+          (quote (foaf alice X)))
+        (list {:X (quote carol)}))
+
+      ;; ── Content ─────────────────────────────────────────────
+      (dl-demo-test-set! "popular posts"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((authored alice p1) (authored bob p2) (authored carol p3)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)
+               (liked u1 p2)))
+            dl-demo-content-rules)
+          (quote (popular P)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "interesting feed"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((follows me alice) (follows me bob)
+               (authored alice p1) (authored bob p2)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)
+               (liked u4 p2)))
+            dl-demo-content-rules)
+          (quote (interesting me P)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "post likes count"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((authored alice p1)
+               (liked u1 p1) (liked u2 p1) (liked u3 p1)))
+            dl-demo-content-rules)
+          (quote (post-likes p1 N)))
+        (list {:N 3}))
+
+      ;; ── Permissions ─────────────────────────────────────────
+      (dl-demo-test-set! "direct group access"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member alice editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote alice)}))
+
+      (dl-demo-test-set! "subgroup access"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member bob writers)
+               (subgroup writers editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote bob)}))
+
+      (dl-demo-test-set! "transitive subgroup"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((member carol drafters)
+               (subgroup drafters writers)
+               (subgroup writers editors)
+               (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list {:X (quote carol)}))
+
+      ;; ── Cooking posts (canonical Phase 10 example) ─────────
+      (dl-demo-test-set! "cooking posts by network"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((follows me alice) (follows alice bob) (follows alice carol)
+               (authored alice p1) (authored bob p2)
+               (authored carol p3) (authored carol p4)
+               (tagged p1 travel) (tagged p2 cooking)
+               (tagged p3 cooking) (tagged p4 books)))
+            dl-demo-cooking-rules)
+          (quote (cooking-post-by-network me P)))
+        (list {:P (quote p2)} {:P (quote p3)}))
+
+      (dl-demo-test-set! "cooking — direct follow only"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((follows me bob)
+               (authored bob p1) (authored bob p2)
+               (tagged p1 cooking) (tagged p2 books)))
+            dl-demo-cooking-rules)
+          (quote (cooking-post-by-network me P)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "cooking — none in network"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((follows me bob)
+               (authored bob p1) (tagged p1 books)))
+            dl-demo-cooking-rules)
+          (quote (cooking-post-by-network me P)))
+        (list))
+
+      ;; ── Tag co-occurrence ──────────────────────────────────
+      (dl-demo-test-set! "cotagged posts"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((tagged p1 cooking) (tagged p1 vegetarian)
+               (tagged p2 cooking) (tagged p2 quick)
+               (tagged p3 vegetarian)))
+            dl-demo-tag-cooccur-rules)
+          (quote (cotagged P cooking vegetarian)))
+        (list {:P (quote p1)}))
+
+      (dl-demo-test-set! "tag pair count"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((tagged p1 cooking) (tagged p1 vegetarian)
+               (tagged p2 cooking) (tagged p2 quick)
+               (tagged p3 cooking) (tagged p3 vegetarian)))
+            dl-demo-tag-cooccur-rules)
+          (quote (tag-pair-count cooking vegetarian N)))
+        (list {:N 2}))
+
+      ;; ── Shortest path on a weighted DAG ──────────────────
+      (dl-demo-test-set! "shortest a→d via DAG"
+        (dl-query
+          (dl-demo-make
+            (quote ((edge a b 5) (edge b c 3) (edge a c 10) (edge c d 2)))
+            dl-demo-shortest-path-rules)
+          (quote (shortest a d W)))
+        (list {:W 10}))
+
+      (dl-demo-test-set! "shortest a→c picks 2-hop"
+        (dl-query
+          (dl-demo-make
+            (quote ((edge a b 5) (edge b c 3) (edge a c 10)))
+            dl-demo-shortest-path-rules)
+          (quote (shortest a c W)))
+        (list {:W 8}))
+
+      (dl-demo-test-set! "shortest unreachable empty"
+        (dl-query
+          (dl-demo-make
+            (quote ((edge a b 5) (edge b c 3)))
+            dl-demo-shortest-path-rules)
+          (quote (shortest a d W)))
+        (list))
+
+      ;; ── Org chart + headcount ─────────────────────────────
+      (dl-demo-test-set! "ceo subordinate transitive"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((manager ic1 mgr1) (manager ic2 mgr1)
+               (manager mgr1 vp1) (manager ic3 vp1)
+               (manager vp1 ceo)))
+            dl-demo-org-rules)
+          (quote (subordinate ceo X)))
+        (list
+          {:X (quote vp1)} {:X (quote mgr1)} {:X (quote ic1)}
+          {:X (quote ic2)} {:X (quote ic3)}))
+
+      (dl-demo-test-set! "ceo headcount = 5"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((manager ic1 mgr1) (manager ic2 mgr1)
+               (manager mgr1 vp1) (manager ic3 vp1)
+               (manager vp1 ceo)))
+            dl-demo-org-rules)
+          (quote (headcount ceo N)))
+        (list {:N 5}))
+
+      (dl-demo-test-set! "mgr1 headcount = 2"
+        (dl-query
+          (dl-demo-make
+            (quote
+              ((manager ic1 mgr1) (manager ic2 mgr1)
+               (manager mgr1 vp1) (manager ic3 vp1)
+               (manager vp1 ceo)))
+            dl-demo-org-rules)
+          (quote (headcount mgr1 N)))
+        (list {:N 2}))
+
+      (dl-demo-test-set! "no access without grant"
+        (dl-query
+          (dl-demo-make
+            (quote ((member dave outsiders) (allowed editors blog)))
+            dl-demo-perm-rules)
+          (quote (can-access X blog)))
+        (list)))))
+
+(define
+  dl-demo-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-demo-pass 0)
+      (set! dl-demo-fail 0)
+      (set! dl-demo-failures (list))
+      (dl-demo-run-all!)
+      {:passed dl-demo-pass
+       :failed dl-demo-fail
+       :total (+ dl-demo-pass dl-demo-fail)
+       :failures dl-demo-failures})))

lib/datalog/tests/eval.sx

@@ -0,0 +1,463 @@
+;; 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)
+      ;; Rule-shape sanity: empty-list head and non-list body raise
+      ;; clear errors rather than crashing inside the saturator.
+      (dl-et-test! "empty head rejected"
+        (dl-et-throws?
+          (fn ()
+            (dl-add-rule! (dl-make-db)
+              {:head (list) :body (list)})))
+        true)
+
+      (dl-et-test! "non-list body rejected"
+        (dl-et-throws?
+          (fn ()
+            (dl-add-rule! (dl-make-db)
+              {:head (list (quote p) (quote X)) :body 42})))
+        true)
+
+      ;; Reserved relation names rejected as rule/fact heads.
+      (dl-et-test!
+        "reserved name `not` as head rejected"
+        (dl-et-throws? (fn () (dl-program "not(X) :- p(X).")))
+        true)
+
+      (dl-et-test!
+        "reserved name `count` as head rejected"
+        (dl-et-throws?
+          (fn () (dl-program "count(N, X, p(X)) :- p(X).")))
+        true)
+
+      (dl-et-test!
+        "reserved name `<` as head rejected"
+        (dl-et-throws? (fn () (dl-program "<(X, 5) :- p(X).")))
+        true)
+
+      (dl-et-test!
+        "reserved name `is` as head rejected"
+        (dl-et-throws? (fn () (dl-program "is(N, +(1, 2)) :- p(N).")))
+        true)
+
+      ;; Body literal with a reserved-name positive head is rejected.
+      ;; The parser only treats outer-level `not(P)` as negation; nested
+      ;; `not(not(P))` would otherwise silently parse as a positive call
+      ;; to a relation named `not` and succeed vacuously. The safety
+      ;; checker now flags this so the user gets a clear error.
+      ;; Body literal with a reserved-name positive head is rejected.
+      ;; The parser only treats outer-level `not(P)` as negation; nested
+      ;; `not(not(P))` would otherwise silently parse as a positive call
+      ;; to a relation named `not` and succeed vacuously — so the safety
+      ;; checker now flags this to give the user a clear error.
+      (dl-et-test!
+        "nested not(not(...)) rejected"
+        (dl-et-throws?
+          (fn ()
+            (dl-program
+              "banned(a). u(a). vip(X) :- u(X), not(not(banned(X))).")))
+        true)
+
+      ;; A dict body literal that isn't `{:neg ...}` is almost always a
+      ;; typo — it would otherwise silently fall through to a confusing
+      ;; head-var-unbound safety error. Now caught with a clear message.
+      (dl-et-test!
+        "dict body lit without :neg rejected"
+        (dl-et-throws?
+          (fn ()
+            (let ((db (dl-make-db)))
+              (dl-add-rule! db
+                {:head (list (quote p) (quote X))
+                 :body (list {:weird "stuff"})}))))
+        true)
+
+      ;; Facts may only have simple-term args (number / string / symbol).
+      ;; A compound arg like `+(1, 2)` would otherwise be silently
+      ;; stored as the unreduced expression `(+ 1 2)` because dl-ground?
+      ;; sees no free variables.
+      (dl-et-test!
+        "compound arg in fact rejected"
+        (dl-et-throws? (fn () (dl-program "p(+(1, 2)).")))
+        true)
+
+      ;; Rule heads may only have variable or constant args — no
+      ;; compounds. Compound heads would be saturated as unreduced
+      ;; tuples rather than the arithmetic result the user expected.
+      (dl-et-test!
+        "compound arg in rule head rejected"
+        (dl-et-throws?
+          (fn () (dl-program "n(3). double(*(X, 2)) :- n(X).")))
+        true)
+
+      ;; The anonymous-variable renamer used to start at `_anon1`
+      ;; unconditionally; a rule that wrote `q(_anon1) :- p(_anon1, _)`
+      ;; (the user picking the same name the renamer would generate)
+      ;; would see the `_` renamed to `_anon1` too, collapsing the
+      ;; two positions in `p(_anon1, _)` to a single var. Now the
+      ;; renamer scans the rule for the max `_anon<N>` and starts past
+      ;; it, so user-written names of that form are preserved.
+      (dl-et-test-set! "anonymous-rename avoids user `_anon` collision"
+        (dl-query
+          (dl-program
+            "p(a, b). p(c, d). q(_anon1) :- p(_anon1, _).")
+          (quote (q X)))
+        (list {:X (quote a)} {:X (quote c)}))
+
+      (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)
+      ;; Underscore in head is unsafe — it's a fresh existential per
+      ;; occurrence after Phase 5d's anonymous-var renaming, and there's
+      ;; nothing in the body to bind it. (Old behavior accepted this by
+      ;; treating '_' as a literal name to skip; the renaming made it an
+      ;; ordinary unbound variable.)
+      (dl-et-test!
+        "underscore in head — unsafe"
+        (dl-et-throws? (fn () (dl-program "p(X, _) :- q(X).")))
+        true)
+      (dl-et-test!
+        "underscore in body only — safe"
+        (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)
+
+      ;; Anonymous variables: each occurrence must be independent.
+      (dl-et-test-set! "anon vars in rule are independent"
+        (dl-query
+          (dl-program
+            "p(a, b). p(c, d). q(X) :- p(X, _), p(_, Y).")
+          (list (quote q) (quote X)))
+        (list {:X (quote a)} {:X (quote c)}))
+
+      (dl-et-test-set! "anon vars in goal are independent"
+        (dl-query
+          (dl-program "p(1, 2, 3). p(4, 5, 6).")
+          (list (quote p) (quote _) (quote X) (quote _)))
+        (list {:X 2} {:X 5}))
+
+      ;; dl-summary: relation -> tuple-count for inspection.
+      (dl-et-test! "dl-summary basic"
+        (dl-summary
+          (let
+            ((db (dl-program "p(1). p(2). q(3).")))
+            (do (dl-saturate! db) db)))
+        {:p 2 :q 1})
+
+      (dl-et-test! "dl-summary empty IDB shown"
+        (dl-summary
+          (let
+            ((db (dl-program "r(X) :- s(X).")))
+            (do (dl-saturate! db) db)))
+        {:r 0})
+
+      (dl-et-test! "dl-summary mixed EDB and IDB"
+        (dl-summary
+          (let
+            ((db (dl-program
+                   "parent(a, b).
+                    ancestor(X, Y) :- parent(X, Y).
+                    ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+            (do (dl-saturate! db) db)))
+        {:parent 1 :ancestor 1})
+
+      (dl-et-test! "dl-summary empty db"
+        (dl-summary (dl-make-db))
+        {})
+
+      ;; Strategy hook: default semi-naive; :magic accepted but
+      ;; falls back to semi-naive (the transformation itself is
+      ;; deferred — Phase 6 in plan).
+      (dl-et-test! "default strategy"
+        (dl-get-strategy (dl-make-db))
+        :semi-naive)
+
+      (dl-et-test! "set strategy"
+        (let ((db (dl-make-db)))
+          (do (dl-set-strategy! db :magic) (dl-get-strategy db)))
+        :magic)
+
+      ;; Unknown strategy values are rejected so typos don't silently
+      ;; fall back to the default.
+      (dl-et-test!
+        "unknown strategy rejected"
+        (dl-et-throws?
+          (fn ()
+            (let ((db (dl-make-db)))
+              (dl-set-strategy! db :semi_naive))))
+        true)
+
+      ;; dl-saturated?: no-work-left predicate.
+      (dl-et-test! "saturated? after saturation"
+        (let ((db (dl-program
+                    "parent(a, b).
+                     ancestor(X, Y) :- parent(X, Y).")))
+          (do (dl-saturate! db) (dl-saturated? db)))
+        true)
+
+      (dl-et-test! "saturated? before saturation"
+        (let ((db (dl-program
+                    "parent(a, b).
+                     ancestor(X, Y) :- parent(X, Y).")))
+          (dl-saturated? db))
+        false)
+
+      ;; Disjunction via multiple rules — Datalog has no `;` in
+      ;; body, so disjunction is expressed as separate rules with
+      ;; the same head. Here plant_based(X) is satisfied by either
+      ;; vegan(X) or vegetarian(X).
+      (dl-et-test-set! "disjunction via multiple rules"
+        (dl-query
+          (dl-program
+            "vegan(alice). vegetarian(bob). meat_eater(carol).
+             plant_based(X) :- vegan(X).
+             plant_based(X) :- vegetarian(X).")
+          (list (quote plant_based) (quote X)))
+        (list {:X (quote alice)} {:X (quote bob)}))
+
+      ;; Bipartite-style join: pair-of-friends who share a hobby.
+      ;; Three-relation join exercising the planner's join order.
+      (dl-et-test-set! "bipartite friends-with-hobby"
+        (dl-query
+          (dl-program
+            "hobby(alice, climb). hobby(bob, paint).
+             hobby(carol, climb).
+             friend(alice, carol). friend(bob, alice).
+             match(A, B, H) :- friend(A, B), hobby(A, H), hobby(B, H).")
+          (list (quote match) (quote A) (quote B) (quote H)))
+        (list {:A (quote alice) :B (quote carol) :H (quote climb)}))
+
+      ;; Repeated variable (diagonal): p(X, X) only matches tuples
+      ;; whose two args are equal. The unifier handles this via the
+      ;; subst chain — first occurrence binds X, second occurrence
+      ;; checks against the binding.
+      (dl-et-test-set! "diagonal query"
+        (dl-query
+          (dl-program "p(1, 1). p(2, 3). p(4, 4). p(5, 5).")
+          (list (quote p) (quote X) (quote X)))
+        (list {:X 1} {:X 4} {:X 5}))
+
+      ;; A relation can be both EDB-seeded and rule-derived;
+      ;; saturate combines facts + derivations.
+      (dl-et-test-set! "mixed EDB + IDB same relation"
+        (dl-query
+          (dl-program
+            "link(a, b). link(c, d). link(e, c).
+             via(a, e).
+             link(X, Y) :- via(X, M), link(M, Y).")
+          (list (quote link) (quote a) (quote X)))
+        (list {:X (quote b)} {:X (quote c)}))
+
+      (dl-et-test! "saturated? after assert"
+        (let ((db (dl-program
+                    "parent(a, b).
+                     ancestor(X, Y) :- parent(X, Y).")))
+          (do
+            (dl-saturate! db)
+            (dl-add-fact! db (list (quote parent) (quote b) (quote c)))
+            (dl-saturated? db)))
+        false)
+
+      (dl-et-test-set! "magic-set still derives correctly"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (do
+            (dl-set-strategy! db :magic)
+            (dl-query db (list (quote ancestor) (quote a) (quote X)))))
+        (list {:X (quote b)} {:X (quote c)})))))
+
+(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})))

lib/datalog/tests/magic.sx

@@ -0,0 +1,528 @@
+;; lib/datalog/tests/magic.sx — adornment + SIPS analysis tests.
+
+(define dl-mt-pass 0)
+(define dl-mt-fail 0)
+(define dl-mt-failures (list))
+
+(define
+  dl-mt-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-mt-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-mt-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-mt-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-mt-deep=? (nth a i) (nth b i))) false)
+      (else (dl-mt-deq-l? a b (+ i 1))))))
+
+(define
+  dl-mt-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-mt-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-mt-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-mt-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-mt-deep=? got expected)
+      (set! dl-mt-pass (+ dl-mt-pass 1))
+      (do
+        (set! dl-mt-fail (+ dl-mt-fail 1))
+        (append!
+          dl-mt-failures
+          (str
+            name
+            "\n    expected: " expected
+            "\n    got:      " got))))))
+
+(define
+  dl-mt-run-all!
+  (fn
+    ()
+    (do
+      ;; Goal adornment.
+      (dl-mt-test! "adorn 0-ary"
+        (dl-adorn-goal (list (quote ready)))
+        "")
+      (dl-mt-test! "adorn all bound"
+        (dl-adorn-goal (list (quote p) 1 2 3))
+        "bbb")
+      (dl-mt-test! "adorn all free"
+        (dl-adorn-goal (list (quote p) (quote X) (quote Y)))
+        "ff")
+      (dl-mt-test! "adorn mixed"
+        (dl-adorn-goal (list (quote ancestor) (quote tom) (quote X)))
+        "bf")
+      (dl-mt-test! "adorn const var const"
+        (dl-adorn-goal (list (quote p) (quote a) (quote X) (quote b)))
+        "bfb")
+
+      ;; dl-adorn-lit with explicit bound set.
+      (dl-mt-test! "adorn lit with bound"
+        (dl-adorn-lit (list (quote p) (quote X) (quote Y)) (list "X"))
+        "bf")
+
+      ;; Rule SIPS — chain ancestor.
+      (dl-mt-test! "sips chain ancestor bf"
+        (dl-rule-sips
+          {:head (list (quote ancestor) (quote X) (quote Z))
+           :body (list (list (quote parent) (quote X) (quote Y))
+                       (list (quote ancestor) (quote Y) (quote Z)))}
+          "bf")
+        (list
+          {:lit (list (quote parent) (quote X) (quote Y)) :adornment "bf"}
+          {:lit (list (quote ancestor) (quote Y) (quote Z)) :adornment "bf"}))
+
+      ;; SIPS — head fully bound.
+      (dl-mt-test! "sips head bb"
+        (dl-rule-sips
+          {:head (list (quote q) (quote X) (quote Y))
+           :body (list (list (quote p) (quote X) (quote Z))
+                       (list (quote r) (quote Z) (quote Y)))}
+          "bb")
+        (list
+          {:lit (list (quote p) (quote X) (quote Z)) :adornment "bf"}
+          {:lit (list (quote r) (quote Z) (quote Y)) :adornment "bb"}))
+
+      ;; SIPS — comparison; vars must be bound by prior body lit.
+      (dl-mt-test! "sips with comparison"
+        (dl-rule-sips
+          {:head (list (quote q) (quote X))
+           :body (list (list (quote p) (quote X))
+                       (list (string->symbol "<") (quote X) 5))}
+          "f")
+        (list
+          {:lit (list (quote p) (quote X)) :adornment "f"}
+          {:lit (list (string->symbol "<") (quote X) 5) :adornment "bb"}))
+
+      ;; SIPS — `is` binds its left arg.
+      (dl-mt-test! "sips with is"
+        (dl-rule-sips
+          {:head (list (quote q) (quote X) (quote Y))
+           :body (list (list (quote p) (quote X))
+                       (list (quote is) (quote Y) (list (string->symbol "+") (quote X) 1)))}
+          "ff")
+        (list
+          {:lit (list (quote p) (quote X)) :adornment "f"}
+          {:lit (list (quote is) (quote Y)
+                      (list (string->symbol "+") (quote X) 1))
+           :adornment "fb"}))
+
+      ;; Magic predicate naming.
+      (dl-mt-test! "magic-rel-name"
+        (dl-magic-rel-name "ancestor" "bf")
+        "magic_ancestor^bf")
+
+      ;; Bound-args extraction.
+      (dl-mt-test! "bound-args bf"
+        (dl-bound-args (list (quote ancestor) (quote tom) (quote X)) "bf")
+        (list (quote tom)))
+
+      (dl-mt-test! "bound-args mixed"
+        (dl-bound-args (list (quote p) 1 (quote Y) 3) "bfb")
+        (list 1 3))
+
+      (dl-mt-test! "bound-args all-free"
+        (dl-bound-args (list (quote p) (quote X) (quote Y)) "ff")
+        (list))
+
+      ;; Magic literal construction.
+      (dl-mt-test! "magic-lit"
+        (dl-magic-lit "ancestor" "bf" (list (quote tom)))
+        (list (string->symbol "magic_ancestor^bf") (quote tom)))
+
+      ;; Magic-sets rewriter: structural sanity.
+      (dl-mt-test! "rewrite ancestor produces seed"
+        (let
+          ((rules
+             (list
+               {:head (list (quote ancestor) (quote X) (quote Y))
+                :body (list (list (quote parent) (quote X) (quote Y)))}
+               {:head (list (quote ancestor) (quote X) (quote Z))
+                :body
+                (list (list (quote parent) (quote X) (quote Y))
+                      (list (quote ancestor) (quote Y) (quote Z)))})))
+          (get
+            (dl-magic-rewrite rules "ancestor" "bf" (list (quote a)))
+            :seed))
+        (list (string->symbol "magic_ancestor^bf") (quote a)))
+
+      ;; Equivalence: rewritten program derives same ancestor tuples.
+      ;; In a chain a→b→c→d, magic-rewritten run still derives all
+      ;; ancestor pairs reachable from any node a/b/c/d propagated via
+      ;; magic_ancestor^bf — i.e. the full closure (6 tuples). Magic
+      ;; saves work only when the EDB has irrelevant nodes outside
+      ;; the seed's transitive cone.
+      (dl-mt-test! "magic-rewritten ancestor count"
+        (let
+          ((rules
+             (list
+               {:head (list (quote ancestor) (quote X) (quote Y))
+                :body (list (list (quote parent) (quote X) (quote Y)))}
+               {:head (list (quote ancestor) (quote X) (quote Z))
+                :body
+                (list (list (quote parent) (quote X) (quote Y))
+                      (list (quote ancestor) (quote Y) (quote Z)))}))
+            (edb (list
+                   (list (quote parent) (quote a) (quote b))
+                   (list (quote parent) (quote b) (quote c))
+                   (list (quote parent) (quote c) (quote d)))))
+          (let
+            ((rewritten (dl-magic-rewrite rules "ancestor" "bf" (list (quote a))))
+              (db (dl-make-db)))
+            (do
+              (for-each (fn (f) (dl-add-fact! db f)) edb)
+              (dl-add-fact! db (get rewritten :seed))
+              (for-each (fn (r) (dl-add-rule! db r)) (get rewritten :rules))
+              (dl-saturate! db)
+              (len (dl-relation db "ancestor")))))
+        6)
+
+      ;; dl-magic-query: end-to-end driver, doesn't mutate caller's db.
+      ;; Magic over a rule with negated body literal — propagation
+      ;; rules generated only for positive lits; negated lits pass
+      ;; through unchanged.
+      (dl-mt-test! "magic over rule with negation"
+        (let
+          ((db (dl-program
+                 "u(a). u(b). u(c). banned(b).
+                  active(X) :- u(X), not(banned(X)).")))
+          (let
+            ((semi (dl-query db (list (quote active) (quote X))))
+              (magic (dl-magic-query db (list (quote active) (quote X)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; All-bound query (existence check) generates an "bb"
+      ;; adornment chain. Verifies the rewriter walks multiple
+      ;; (rel, adn) pairs through the worklist.
+      (dl-mt-test! "magic existence check via bb"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c). parent(c, d).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (let
+            ((found (dl-magic-query
+                      db (list (quote ancestor) (quote a) (quote c))))
+              (missing (dl-magic-query
+                         db (list (quote ancestor) (quote a) (quote z)))))
+            (and (= (len found) 1) (= (len missing) 0))))
+        true)
+
+      ;; Magic equivalence on the federation demo.
+      (dl-mt-test! "magic ≡ semi on foaf demo"
+        (let
+          ((db (dl-program-data
+                 (quote ((follows alice bob)
+                         (follows bob carol)
+                         (follows alice dave)))
+                 dl-demo-federation-rules)))
+          (let
+            ((semi (dl-query db (quote (foaf alice X))))
+              (magic (dl-magic-query db (quote (foaf alice X)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Shape validation: dl-magic-query rejects non-list / non-
+      ;; dict goal shapes cleanly rather than crashing in `rest`.
+      (dl-mt-test! "magic rejects string goal"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-magic-query (dl-make-db) "foo"))
+            threw))
+        true)
+
+      (dl-mt-test! "magic rejects bare dict goal"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-magic-query (dl-make-db) {:foo "bar"}))
+            threw))
+        true)
+
+      ;; 3-stratum program under magic — distinct rule heads at
+      ;; strata 0/1/2 must all rewrite via the worklist.
+      (dl-mt-test! "magic 3-stratum program"
+        (let
+          ((db (dl-program
+                 "a(1). a(2). a(3). b(2).
+                  c(X) :- a(X), not(b(X)).
+                  d(X) :- c(X), not(banned(X)).
+                  banned(3).")))
+          (let
+            ((semi (dl-query db (list (quote d) (quote X))))
+              (magic (dl-magic-query db (list (quote d) (quote X)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Aggregate -> derived -> threshold chain via magic.
+      (dl-mt-test! "magic aggregate-derived chain"
+        (let
+          ((db (dl-program
+                 "src(1). src(2). src(3).
+                  cnt(N) :- count(N, X, src(X)).
+                  active(N) :- cnt(N), >=(N, 2).")))
+          (let
+            ((semi (dl-query db (list (quote active) (quote N))))
+              (magic (dl-magic-query db (list (quote active) (quote N)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Multi-relation rewrite chain: query r4 → propagate to r3,
+      ;; r2, r1, a. The worklist must process all of them; an
+      ;; earlier bug stopped after only the head pair.
+      (dl-mt-test! "magic chain through 4 rule levels"
+        (let
+          ((db (dl-program
+                 "a(1). a(2). r1(X) :- a(X). r2(X) :- r1(X).
+                  r3(X) :- r2(X). r4(X) :- r3(X).")))
+          (= 2 (len (dl-magic-query db (list (quote r4) (quote X))))))
+        true)
+
+      ;; Shortest-path demo via magic — exercises the rewriter
+      ;; against rules that mix recursive positive lits with an
+      ;; aggregate body literal.
+      (dl-mt-test! "magic on shortest-path demo"
+        (let
+          ((db (dl-program-data
+                 (quote ((edge a b 5) (edge b c 3) (edge a c 10)))
+                 dl-demo-shortest-path-rules)))
+          (let
+            ((semi (dl-query db (quote (shortest a c W))))
+              (magic (dl-magic-query db (quote (shortest a c W)))))
+            (and (= (len semi) (len magic))
+                 (= (len semi) 1))))
+        true)
+
+      ;; Same relation called with different adornment patterns
+      ;; in different rules. The worklist must enqueue and process
+      ;; each (rel, adornment) pair.
+      (dl-mt-test! "magic with multi-adornment same relation"
+        (let
+          ((db (dl-program
+                 "parent(p1, alice). parent(p2, bob).
+                  parent(g, p1). parent(g, p2).
+                  sibling(P1, P2) :- parent(G, P1), parent(G, P2),
+                                     !=(P1, P2).
+                  cousin(X, Y) :- parent(P1, X), parent(P2, Y),
+                                  sibling(P1, P2).")))
+          (let
+            ((semi (dl-query db (list (quote cousin) (quote alice) (quote Y))))
+              (magic (dl-magic-query db (list (quote cousin) (quote alice) (quote Y)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Magic over a rule whose body contains an aggregate.
+      ;; The rewriter passes aggregate body lits through unchanged
+      ;; (no propagation generated for them), so semi-naive's count
+      ;; logic still fires correctly under the rewritten program.
+      (dl-mt-test! "magic over rule with aggregate body"
+        (let
+          ((db (dl-program
+                 "post(p1). post(p2). post(p3).
+                  liked(u1, p1). liked(u2, p1). liked(u3, p1).
+                  liked(u1, p2).
+                  rich(P) :- post(P), count(N, U, liked(U, P)),
+                             >=(N, 2).")))
+          (let
+            ((semi (dl-query db (list (quote rich) (quote P))))
+              (magic (dl-magic-query db (list (quote rich) (quote P)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; Mixed EDB + IDB: a relation can be both EDB-seeded and
+      ;; rule-derived. dl-magic-query must include the EDB portion
+      ;; even though the relation has rules.
+      (dl-mt-test! "magic mixed EDB+IDB"
+        (len
+          (dl-magic-query
+            (dl-program
+              "link(a, b). link(c, d). link(e, c).
+               via(a, e).
+               link(X, Y) :- via(X, M), link(M, Y).")
+            (list (quote link) (quote a) (quote X))))
+        2)
+
+      ;; dl-magic-query falls back to dl-query for built-in,
+      ;; aggregate, and negation goals (the magic seed would
+      ;; otherwise be non-ground).
+      (dl-mt-test! "magic-query falls back on aggregate"
+        (let
+          ((r (dl-magic-query
+                (dl-program "p(1). p(2). p(3).")
+                (list (quote count) (quote N) (quote X)
+                      (list (quote p) (quote X))))))
+          (and (= (len r) 1) (= (get (first r) "N") 3)))
+        true)
+
+      (dl-mt-test! "magic-query equivalent to dl-query"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c). parent(c, d).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (let
+            ((semi (dl-query db (list (quote ancestor) (quote a) (quote X))))
+              (magic (dl-magic-query
+                       db (list (quote ancestor) (quote a) (quote X)))))
+            (= (len semi) (len magic))))
+        true)
+
+      ;; The magic rewriter passes aggregate body lits through
+      ;; unchanged, so an aggregate over an IDB relation would see an
+      ;; empty inner-goal in the magic db unless the IDB is already
+      ;; materialised. dl-magic-query now pre-saturates the source db
+      ;; to guarantee equivalence with dl-query for every stratified
+      ;; program. Previously this returned `({:N 0})` because `active`
+      ;; (IDB, derived through negation) was never derived in the
+      ;; magic db.
+      (dl-mt-test! "magic over aggregate-of-IDB matches vanilla"
+        (let
+          ((src
+             "u(a). u(b). u(c). u(d). banned(b). banned(d).
+              active(X) :- u(X), not(banned(X)).
+              n(N) :- count(N, X, active(X))."))
+          (let
+            ((vanilla (dl-eval src "?- n(N)."))
+              (magic (dl-eval-magic src "?- n(N).")))
+            (and (= (len vanilla) 1)
+                 (= (len magic) 1)
+                 (= (get (first vanilla) "N")
+                    (get (first magic) "N")))))
+        true)
+
+      ;; magic-query doesn't mutate caller db.
+      (dl-mt-test! "magic-query preserves caller db"
+        (let
+          ((db (dl-program
+                 "parent(a, b). parent(b, c).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (let
+            ((rules-before (len (dl-rules db))))
+            (do
+              (dl-magic-query db (list (quote ancestor) (quote a) (quote X)))
+              (= rules-before (len (dl-rules db))))))
+        true)
+
+      ;; Magic-sets benefit: query touches only one cluster of a
+      ;; multi-component graph. Semi-naive derives the full closure
+      ;; over both clusters; magic only the seeded one.
+      ;; Magic-vs-semi work shape: chain of 12. Semi-naive
+      ;; derives the full closure (78 = 12·13/2). A magic query
+      ;; rooted at node 0 returns the 12 descendants only —
+      ;; demonstrating that magic limits derivation to the
+      ;; query's transitive cone.
+      (dl-mt-test! "magic vs semi work-shape on chain-12"
+        (let
+          ((source (str
+                     "parent(0, 1). parent(1, 2). parent(2, 3). "
+                     "parent(3, 4). parent(4, 5). parent(5, 6). "
+                     "parent(6, 7). parent(7, 8). parent(8, 9). "
+                     "parent(9, 10). parent(10, 11). parent(11, 12). "
+                     "ancestor(X, Y) :- parent(X, Y). "
+                     "ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (let
+            ((db1 (dl-make-db)) (db2 (dl-make-db)))
+            (do
+              (dl-load-program! db1 source)
+              (dl-saturate! db1)
+              (dl-load-program! db2 source)
+              (let
+                ((semi-count (len (dl-relation db1 "ancestor")))
+                  (magic-count
+                    (len (dl-magic-query
+                           db2 (list (quote ancestor) 0 (quote X))))))
+                ;; Magic returns only descendants of 0 (12 of them).
+                (and (= semi-count 78) (= magic-count 12))))))
+        true)
+
+      ;; Magic + arithmetic: rules with `is` clauses pass through
+      ;; the rewriter unchanged (built-ins aren't propagated).
+      (dl-mt-test! "magic preserves arithmetic"
+        (let
+          ((source "n(1). n(2). n(3).
+                    doubled(X, Y) :- n(X), is(Y, *(X, 2))."))
+          (let
+            ((semi (dl-eval source "?- doubled(2, Y)."))
+              (magic (dl-eval-magic source "?- doubled(2, Y).")))
+            (= (len semi) (len magic))))
+        true)
+
+      (dl-mt-test! "magic skips irrelevant clusters"
+        (let
+          ;; Two disjoint chains. Query is rooted in cluster 1.
+          ((db (dl-program
+                 "parent(a, b). parent(b, c).
+                  parent(x, y). parent(y, z).
+                  ancestor(X, Y) :- parent(X, Y).
+                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (do
+            (dl-saturate! db)
+            (let
+              ((semi-count (len (dl-relation db "ancestor")))
+                (magic-results
+                  (dl-magic-query
+                    db (list (quote ancestor) (quote a) (quote X)))))
+              ;; Semi-naive derives 6 (3 in each cluster). Magic
+              ;; gives 3 query results (a's reachable: b, c).
+              (and (= semi-count 6) (= (len magic-results) 2)))))
+        true)
+
+      (dl-mt-test! "magic-rewritten finds same answers"
+        (let
+          ((rules
+             (list
+               {:head (list (quote ancestor) (quote X) (quote Y))
+                :body (list (list (quote parent) (quote X) (quote Y)))}
+               {:head (list (quote ancestor) (quote X) (quote Z))
+                :body
+                (list (list (quote parent) (quote X) (quote Y))
+                      (list (quote ancestor) (quote Y) (quote Z)))}))
+            (edb (list
+                   (list (quote parent) (quote a) (quote b))
+                   (list (quote parent) (quote b) (quote c)))))
+          (let
+            ((rewritten (dl-magic-rewrite rules "ancestor" "bf" (list (quote a))))
+              (db (dl-make-db)))
+            (do
+              (for-each (fn (f) (dl-add-fact! db f)) edb)
+              (dl-add-fact! db (get rewritten :seed))
+              (for-each (fn (r) (dl-add-rule! db r)) (get rewritten :rules))
+              (dl-saturate! db)
+              (len (dl-query db (list (quote ancestor) (quote a) (quote X)))))))
+        2))))
+
+(define
+  dl-magic-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-mt-pass 0)
+      (set! dl-mt-fail 0)
+      (set! dl-mt-failures (list))
+      (dl-mt-run-all!)
+      {:passed dl-mt-pass
+       :failed dl-mt-fail
+       :total (+ dl-mt-pass dl-mt-fail)
+       :failures dl-mt-failures})))

lib/datalog/tests/negation.sx

@@ -0,0 +1,252 @@
+;; lib/datalog/tests/negation.sx — stratified negation tests.
+
+(define dl-nt-pass 0)
+(define dl-nt-fail 0)
+(define dl-nt-failures (list))
+
+(define
+  dl-nt-deep=?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-nt-deq-l? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-nt-deq-d? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-nt-deq-l?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-nt-deep=? (nth a i) (nth b i))) false)
+      (else (dl-nt-deq-l? a b (+ i 1))))))
+
+(define
+  dl-nt-deq-d?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i)))
+         (not (dl-nt-deep=? (get a k) (get b k))))
+        false)
+      (else (dl-nt-deq-d? a b ka (+ i 1))))))
+
+(define
+  dl-nt-set=?
+  (fn
+    (a b)
+    (and
+      (= (len a) (len b))
+      (dl-nt-subset? a b)
+      (dl-nt-subset? b a))))
+
+(define
+  dl-nt-subset?
+  (fn
+    (xs ys)
+    (cond
+      ((= (len xs) 0) true)
+      ((not (dl-nt-contains? ys (first xs))) false)
+      (else (dl-nt-subset? (rest xs) ys)))))
+
+(define
+  dl-nt-contains?
+  (fn
+    (xs target)
+    (cond
+      ((= (len xs) 0) false)
+      ((dl-nt-deep=? (first xs) target) true)
+      (else (dl-nt-contains? (rest xs) target)))))
+
+(define
+  dl-nt-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-nt-deep=? got expected)
+      (set! dl-nt-pass (+ dl-nt-pass 1))
+      (do
+        (set! dl-nt-fail (+ dl-nt-fail 1))
+        (append!
+          dl-nt-failures
+          (str
+            name
+            "\n    expected: " expected
+            "\n    got:      " got))))))
+
+(define
+  dl-nt-test-set!
+  (fn
+    (name got expected)
+    (if
+      (dl-nt-set=? got expected)
+      (set! dl-nt-pass (+ dl-nt-pass 1))
+      (do
+        (set! dl-nt-fail (+ dl-nt-fail 1))
+        (append!
+          dl-nt-failures
+          (str
+            name
+            "\n    expected (set): " expected
+            "\n    got:            " got))))))
+
+(define
+  dl-nt-throws?
+  (fn
+    (thunk)
+    (let
+      ((threw false))
+      (do
+        (guard
+          (e (#t (set! threw true)))
+          (thunk))
+        threw))))
+
+(define
+  dl-nt-run-all!
+  (fn
+    ()
+    (do
+      ;; Negation against EDB-only relation.
+      (dl-nt-test-set! "not against EDB"
+        (dl-query
+          (dl-program
+            "p(1). p(2). p(3). r(2).
+             q(X) :- p(X), not(r(X)).")
+          (list (quote q) (quote X)))
+        (list {:X 1} {:X 3}))
+
+      ;; Negation against derived relation — needs stratification.
+      (dl-nt-test-set! "not against derived rel"
+        (dl-query
+          (dl-program
+            "p(1). p(2). p(3). s(2).
+             r(X) :- s(X).
+             q(X) :- p(X), not(r(X)).")
+          (list (quote q) (quote X)))
+        (list {:X 1} {:X 3}))
+
+      ;; Two-step strata: r derives via s; q derives via not r.
+      (dl-nt-test-set! "two-step strata"
+        (dl-query
+          (dl-program
+            "node(a). node(b). node(c). node(d).
+             edge(a, b). edge(b, c). edge(c, a).
+             reach(X, Y) :- edge(X, Y).
+             reach(X, Z) :- edge(X, Y), reach(Y, Z).
+             unreachable(X) :- node(X), not(reach(a, X)).")
+          (list (quote unreachable) (quote X)))
+        (list {:X (quote d)}))
+
+      ;; Combine negation with arithmetic and comparison.
+      (dl-nt-test-set! "negation with arithmetic"
+        (dl-query
+          (dl-program
+            "n(1). n(2). n(3). n(4). n(5). odd(1). odd(3). odd(5).
+             even(X) :- n(X), not(odd(X)).")
+          (list (quote even) (quote X)))
+        (list {:X 2} {:X 4}))
+
+      ;; Empty negation result.
+      (dl-nt-test-set! "negation always succeeds"
+        (dl-query
+          (dl-program
+            "p(1). p(2). q(X) :- p(X), not(r(X)).")
+          (list (quote q) (quote X)))
+        (list {:X 1} {:X 2}))
+
+      ;; Negation always fails.
+      (dl-nt-test-set! "negation always fails"
+        (dl-query
+          (dl-program
+            "p(1). p(2). r(1). r(2). q(X) :- p(X), not(r(X)).")
+          (list (quote q) (quote X)))
+        (list))
+
+      ;; Anonymous `_` in a negated literal is existentially quantified
+      ;; — it doesn't need to be bound by an earlier body lit. Without
+      ;; this exemption the safety check would reject the common idiom
+      ;; `orphan(X) :- person(X), not(parent(X, _))`.
+      (dl-nt-test-set! "negation with anonymous var — orphan idiom"
+        (dl-query
+          (dl-program
+            "person(a). person(b). person(c). parent(a, b).
+             orphan(X) :- person(X), not(parent(X, _)).")
+          (list (quote orphan) (quote X)))
+        (list {:X (quote b)} {:X (quote c)}))
+
+      ;; Multiple anonymous vars are each independently existential.
+      (dl-nt-test-set! "negation with multiple anonymous vars"
+        (dl-query
+          (dl-program
+            "u(a). u(b). u(c). edge(a, x). edge(b, y).
+             solo(X) :- u(X), not(edge(X, _)).")
+          (list (quote solo) (quote X)))
+        (list {:X (quote c)}))
+
+      ;; Stratifiability checks.
+      (dl-nt-test! "non-stratifiable rejected"
+        (dl-nt-throws?
+          (fn ()
+            (let ((db (dl-make-db)))
+              (do
+                (dl-add-rule!
+                  db
+                  {:head (list (quote p) (quote X))
+                   :body (list (list (quote q) (quote X))
+                               {:neg (list (quote r) (quote X))})})
+                (dl-add-rule!
+                  db
+                  {:head (list (quote r) (quote X))
+                   :body (list (list (quote p) (quote X)))})
+                (dl-add-fact! db (list (quote q) 1))
+                (dl-saturate! db)))))
+        true)
+
+      (dl-nt-test! "stratifiable accepted"
+        (dl-nt-throws?
+          (fn ()
+            (dl-program
+              "p(1). p(2). r(2).
+               q(X) :- p(X), not(r(X)).")))
+        false)
+
+      ;; Multi-stratum chain.
+      (dl-nt-test-set! "three-level strata"
+        (dl-query
+          (dl-program
+            "a(1). a(2). a(3). a(4).
+             b(X) :- a(X), not(c(X)).
+             c(X) :- d(X).
+             d(2).
+             d(4).")
+          (list (quote b) (quote X)))
+        (list {:X 1} {:X 3}))
+
+      ;; Safety violation: negation refers to unbound var.
+      (dl-nt-test! "negation safety violation"
+        (dl-nt-throws?
+          (fn ()
+            (dl-program
+              "p(1). q(X) :- p(X), not(r(Y)).")))
+        true))))
+
+(define
+  dl-negation-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-nt-pass 0)
+      (set! dl-nt-fail 0)
+      (set! dl-nt-failures (list))
+      (dl-nt-run-all!)
+      {:passed dl-nt-pass
+       :failed dl-nt-fail
+       :total (+ dl-nt-pass dl-nt-fail)
+       :failures dl-nt-failures})))

lib/datalog/tests/parse.sx

@@ -0,0 +1,179 @@
+;; lib/datalog/tests/parse.sx — parser unit tests
+;;
+;; Run via: bash lib/datalog/conformance.sh
+;; Or:      (load "lib/datalog/tokenizer.sx") (load "lib/datalog/parser.sx")
+;;          (load "lib/datalog/tests/parse.sx") (dl-parse-tests-run!)
+
+(define dl-pt-pass 0)
+(define dl-pt-fail 0)
+(define dl-pt-failures (list))
+
+;; Order-independent structural equality. Lists compared positionally,
+;; dicts as sets of (key, value) pairs. Numbers via = (so 30.0 = 30).
+(define
+  dl-deep-equal?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-deep-equal-list? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let
+          ((ka (keys a)) (kb (keys b)))
+          (and
+            (= (len ka) (len kb))
+            (dl-deep-equal-dict? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-deep-equal-list?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-deep-equal? (nth a i) (nth b i))) false)
+      (else (dl-deep-equal-list? a b (+ i 1))))))
+
+(define
+  dl-deep-equal-dict?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i))) (not (dl-deep-equal? (get a k) (get b k))))
+        false)
+      (else (dl-deep-equal-dict? a b ka (+ i 1))))))
+
+(define
+  dl-pt-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-deep-equal? got expected)
+      (set! dl-pt-pass (+ dl-pt-pass 1))
+      (do
+        (set! dl-pt-fail (+ dl-pt-fail 1))
+        (append!
+          dl-pt-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define
+  dl-pt-throws?
+  (fn
+    (thunk)
+    (let
+      ((threw false))
+      (do (guard (e (#t (set! threw true))) (thunk)) threw))))
+
+(define
+  dl-pt-run-all!
+  (fn
+    ()
+    (do
+      (dl-pt-test! "empty program" (dl-parse "") (list))
+      (dl-pt-test! "fact" (dl-parse "parent(tom, bob).") (list {:body (list) :head (list (quote parent) (quote tom) (quote bob))}))
+      (dl-pt-test!
+        "two facts"
+        (dl-parse "parent(tom, bob). parent(bob, ann).")
+        (list {:body (list) :head (list (quote parent) (quote tom) (quote bob))} {:body (list) :head (list (quote parent) (quote bob) (quote ann))}))
+      (dl-pt-test! "zero-ary fact" (dl-parse "ready.") (list {:body (list) :head (list (quote ready))}))
+      (dl-pt-test!
+        "rule one body lit"
+        (dl-parse "ancestor(X, Y) :- parent(X, Y).")
+        (list {:body (list (list (quote parent) (quote X) (quote Y))) :head (list (quote ancestor) (quote X) (quote Y))}))
+      (dl-pt-test!
+        "recursive rule"
+        (dl-parse "ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")
+        (list {:body (list (list (quote parent) (quote X) (quote Y)) (list (quote ancestor) (quote Y) (quote Z))) :head (list (quote ancestor) (quote X) (quote Z))}))
+      (dl-pt-test!
+        "query single"
+        (dl-parse "?- ancestor(tom, X).")
+        (list {:query (list (list (quote ancestor) (quote tom) (quote X)))}))
+      (dl-pt-test!
+        "query multi"
+        (dl-parse "?- p(X), q(X).")
+        (list {:query (list (list (quote p) (quote X)) (list (quote q) (quote X)))}))
+      (dl-pt-test!
+        "negation"
+        (dl-parse "safe(X) :- person(X), not(parent(X, _)).")
+        (list {:body (list (list (quote person) (quote X)) {:neg (list (quote parent) (quote X) (quote _))}) :head (list (quote safe) (quote X))}))
+      (dl-pt-test!
+        "number arg"
+        (dl-parse "age(alice, 30).")
+        (list {:body (list) :head (list (quote age) (quote alice) 30)}))
+      (dl-pt-test!
+        "string arg"
+        (dl-parse "label(x, \"hi\").")
+        (list {:body (list) :head (list (quote label) (quote x) "hi")}))
+      ;; Quoted 'atoms' parse as strings — a uppercase-starting name
+      ;; in quotes used to misclassify as a variable and reject the
+      ;; fact as non-ground.
+      (dl-pt-test!
+        "quoted atom arg parses as string"
+        (dl-parse "p('Hello World').")
+        (list {:body (list) :head (list (quote p) "Hello World")}))
+      (dl-pt-test!
+        "comparison literal"
+        (dl-parse "p(X) :- <(X, 5).")
+        (list {:body (list (list (string->symbol "<") (quote X) 5)) :head (list (quote p) (quote X))}))
+      (dl-pt-test!
+        "is with arith"
+        (dl-parse "succ(X, Y) :- nat(X), is(Y, +(X, 1)).")
+        (list {:body (list (list (quote nat) (quote X)) (list (quote is) (quote Y) (list (string->symbol "+") (quote X) 1))) :head (list (quote succ) (quote X) (quote Y))}))
+      (dl-pt-test!
+        "mixed program"
+        (dl-parse "p(a). p(b). q(X) :- p(X). ?- q(Y).")
+        (list {:body (list) :head (list (quote p) (quote a))} {:body (list) :head (list (quote p) (quote b))} {:body (list (list (quote p) (quote X))) :head (list (quote q) (quote X))} {:query (list (list (quote q) (quote Y)))}))
+      (dl-pt-test!
+        "comments skipped"
+        (dl-parse "% comment\nfoo(a).\n/* block */ bar(b).")
+        (list {:body (list) :head (list (quote foo) (quote a))} {:body (list) :head (list (quote bar) (quote b))}))
+      (dl-pt-test!
+        "underscore var"
+        (dl-parse "p(X) :- q(X, _).")
+        (list {:body (list (list (quote q) (quote X) (quote _))) :head (list (quote p) (quote X))}))
+      ;; Negative number literals parse as one negative number,
+      ;; while subtraction (`-(X, Y)`) compound is preserved.
+      (dl-pt-test!
+        "negative integer literal"
+        (dl-parse "n(-3).")
+        (list {:head (list (quote n) -3) :body (list)}))
+
+      (dl-pt-test!
+        "subtraction compound preserved"
+        (dl-parse "r(X) :- is(X, -(10, 3)).")
+        (list
+          {:head (list (quote r) (quote X))
+           :body (list (list (quote is) (quote X)
+                             (list (string->symbol "-") 10 3)))}))
+
+      (dl-pt-test!
+        "number as relation name raises"
+        (dl-pt-throws? (fn () (dl-parse "1(X) :- p(X).")))
+        true)
+
+      (dl-pt-test!
+        "var as relation name raises"
+        (dl-pt-throws? (fn () (dl-parse "P(X).")))
+        true)
+
+      (dl-pt-test!
+        "missing dot raises"
+        (dl-pt-throws? (fn () (dl-parse "p(a)")))
+        true)
+      (dl-pt-test!
+        "trailing comma raises"
+        (dl-pt-throws? (fn () (dl-parse "p(a,).")))
+        true))))
+
+(define
+  dl-parse-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-pt-pass 0)
+      (set! dl-pt-fail 0)
+      (set! dl-pt-failures (list))
+      (dl-pt-run-all!)
+      {:failures dl-pt-failures :total (+ dl-pt-pass dl-pt-fail) :passed dl-pt-pass :failed dl-pt-fail})))

lib/datalog/tests/semi_naive.sx

@@ -0,0 +1,153 @@
+;; lib/datalog/tests/semi_naive.sx — semi-naive correctness vs naive.
+;;
+;; Strategy: differential — run both saturators on each program and
+;; compare the resulting per-relation tuple counts. Counting (not
+;; element-wise set equality) keeps the suite fast under the bundled
+;; conformance session; correctness on the inhabitants is covered by
+;; eval.sx and builtins.sx (which use dl-saturate! by default — the
+;; semi-naive saturator).
+
+(define dl-sn-pass 0)
+(define dl-sn-fail 0)
+(define dl-sn-failures (list))
+
+(define
+  dl-sn-test!
+  (fn
+    (name got expected)
+    (if
+      (equal? got expected)
+      (set! dl-sn-pass (+ dl-sn-pass 1))
+      (do
+        (set! dl-sn-fail (+ dl-sn-fail 1))
+        (append!
+          dl-sn-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+;; Load `source` into both a semi-naive and a naive db and return a
+;; list of (rel-name semi-count naive-count) triples. Both sets must
+;; have the same union of relation names.
+(define
+  dl-sn-counts
+  (fn
+    (source)
+    (let
+      ((db-s (dl-program source)) (db-n (dl-program source)))
+      (do
+        (dl-saturate! db-s)
+        (dl-saturate-naive! db-n)
+        (let
+          ((out (list)))
+          (do
+            (for-each
+              (fn
+                (k)
+                (append!
+                  out
+                  (list
+                    k
+                    (len (dl-relation db-s k))
+                    (len (dl-relation db-n k)))))
+              (keys (get db-s :facts)))
+            out))))))
+
+(define
+  dl-sn-counts-agree?
+  (fn
+    (counts)
+    (cond
+      ((= (len counts) 0) true)
+      (else
+        (let
+          ((row (first counts)))
+          (and
+            (= (nth row 1) (nth row 2))
+            (dl-sn-counts-agree? (rest counts))))))))
+
+(define
+  dl-sn-chain-source
+  (fn
+    (n)
+    (let
+      ((parts (list "")))
+      (do
+        (define
+          dl-sn-loop
+          (fn
+            (i)
+            (when
+              (< i n)
+              (do
+                (append! parts (str "parent(" i ", " (+ i 1) "). "))
+                (dl-sn-loop (+ i 1))))))
+        (dl-sn-loop 0)
+        (str
+          (join "" parts)
+          "ancestor(X, Y) :- parent(X, Y). "
+          "ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))))
+
+(define
+  dl-sn-run-all!
+  (fn
+    ()
+    (do
+      (dl-sn-test!
+        "ancestor closure counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "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)."))
+        true)
+      (dl-sn-test!
+        "cyclic reach counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "edge(1, 2). edge(2, 3). edge(3, 1). edge(3, 4).\n             reach(X, Y) :- edge(X, Y).\n             reach(X, Z) :- edge(X, Y), reach(Y, Z)."))
+        true)
+      (dl-sn-test!
+        "same-gen counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "parent(a, b). parent(a, c). parent(b, d). parent(c, e).\n             person(a). person(b). person(c). person(d). person(e).\n             sg(X, X) :- person(X).\n             sg(X, Y) :- parent(P1, X), sg(P1, P2), parent(P2, Y)."))
+        true)
+      (dl-sn-test!
+        "rules with builtins counts match"
+        (dl-sn-counts-agree?
+          (dl-sn-counts
+            "n(1). n(2). n(3). n(4). n(5).\n             small(X) :- n(X), <(X, 5).\n             succ(X, Y) :- n(X), <(X, 5), is(Y, +(X, 1))."))
+        true)
+      (dl-sn-test!
+        "static rule fires under semi-naive"
+        (dl-sn-counts-agree?
+          (dl-sn-counts "p(a). p(b). q(X) :- p(X), =(X, a)."))
+        true)
+      ;; Chain length 12 — multiple semi-naive iterations against
+      ;; the recursive ancestor rule (differential vs naive).
+      (dl-sn-test!
+        "chain-12 ancestor counts match"
+        (dl-sn-counts-agree? (dl-sn-counts (dl-sn-chain-source 12)))
+        true)
+      ;; Chain length 25 — semi-naive only — first-arg index makes
+      ;; this tractable in conformance budget.
+      (dl-sn-test!
+        "chain-25 ancestor count value (semi only)"
+        (let
+          ((db (dl-program (dl-sn-chain-source 25))))
+          (do (dl-saturate! db) (len (dl-relation db "ancestor"))))
+        325)
+      (dl-sn-test!
+        "query through semi saturate"
+        (let
+          ((db (dl-program "parent(a, b). parent(b, c).\n                  ancestor(X, Y) :- parent(X, Y).\n                  ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).")))
+          (len (dl-query db (list (quote ancestor) (quote a) (quote X)))))
+        2))))
+
+(define
+  dl-semi-naive-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-sn-pass 0)
+      (set! dl-sn-fail 0)
+      (set! dl-sn-failures (list))
+      (dl-sn-run-all!)
+      {:failures dl-sn-failures :total (+ dl-sn-pass dl-sn-fail) :passed dl-sn-pass :failed dl-sn-fail})))

lib/datalog/tests/tokenize.sx

@@ -0,0 +1,189 @@
+;; lib/datalog/tests/tokenize.sx — tokenizer unit tests
+;;
+;; Run via: bash lib/datalog/conformance.sh
+;; Or:      (load "lib/datalog/tokenizer.sx") (load "lib/datalog/tests/tokenize.sx")
+;;          (dl-tokenize-tests-run!)
+
+(define dl-tk-pass 0)
+(define dl-tk-fail 0)
+(define dl-tk-failures (list))
+
+(define
+  dl-tk-test!
+  (fn
+    (name got expected)
+    (if
+      (= got expected)
+      (set! dl-tk-pass (+ dl-tk-pass 1))
+      (do
+        (set! dl-tk-fail (+ dl-tk-fail 1))
+        (append!
+          dl-tk-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define dl-tk-types (fn (toks) (map (fn (t) (get t :type)) toks)))
+(define dl-tk-values (fn (toks) (map (fn (t) (get t :value)) toks)))
+
+(define
+  dl-tk-run-all!
+  (fn
+    ()
+    (do
+      (dl-tk-test! "empty" (dl-tk-types (dl-tokenize "")) (list "eof"))
+      (dl-tk-test!
+        "atom dot"
+        (dl-tk-types (dl-tokenize "foo."))
+        (list "atom" "punct" "eof"))
+      (dl-tk-test!
+        "atom dot value"
+        (dl-tk-values (dl-tokenize "foo."))
+        (list "foo" "." nil))
+      (dl-tk-test!
+        "var"
+        (dl-tk-types (dl-tokenize "X."))
+        (list "var" "punct" "eof"))
+      (dl-tk-test!
+        "underscore var"
+        (dl-tk-types (dl-tokenize "_x."))
+        (list "var" "punct" "eof"))
+      (dl-tk-test!
+        "integer"
+        (dl-tk-values (dl-tokenize "42"))
+        (list 42 nil))
+      (dl-tk-test!
+        "decimal"
+        (dl-tk-values (dl-tokenize "3.14"))
+        (list 3.14 nil))
+      (dl-tk-test!
+        "string"
+        (dl-tk-values (dl-tokenize "\"hello\""))
+        (list "hello" nil))
+      ;; Quoted 'atoms' tokenize as strings — see the type-table
+      ;; comment in lib/datalog/tokenizer.sx for the rationale.
+      (dl-tk-test!
+        "quoted atom as string"
+        (dl-tk-types (dl-tokenize "'two words'"))
+        (list "string" "eof"))
+      (dl-tk-test!
+        "quoted atom value"
+        (dl-tk-values (dl-tokenize "'two words'"))
+        (list "two words" nil))
+      ;; A quoted atom whose name would otherwise be a variable
+      ;; (uppercase / leading underscore) is now safely a string —
+      ;; this was the bug that motivated the type change.
+      (dl-tk-test!
+        "quoted Uppercase as string"
+        (dl-tk-types (dl-tokenize "'Hello'"))
+        (list "string" "eof"))
+      (dl-tk-test! ":-" (dl-tk-values (dl-tokenize ":-")) (list ":-" nil))
+      (dl-tk-test! "?-" (dl-tk-values (dl-tokenize "?-")) (list "?-" nil))
+      (dl-tk-test! "<=" (dl-tk-values (dl-tokenize "<=")) (list "<=" nil))
+      (dl-tk-test! ">=" (dl-tk-values (dl-tokenize ">=")) (list ">=" nil))
+      (dl-tk-test! "!=" (dl-tk-values (dl-tokenize "!=")) (list "!=" nil))
+      (dl-tk-test!
+        "single op values"
+        (dl-tk-values (dl-tokenize "< > = + - * /"))
+        (list "<" ">" "=" "+" "-" "*" "/" nil))
+      (dl-tk-test!
+        "single op types"
+        (dl-tk-types (dl-tokenize "< > = + - * /"))
+        (list "op" "op" "op" "op" "op" "op" "op" "eof"))
+      (dl-tk-test!
+        "punct"
+        (dl-tk-values (dl-tokenize "( ) , ."))
+        (list "(" ")" "," "." nil))
+      (dl-tk-test!
+        "fact tokens"
+        (dl-tk-types (dl-tokenize "parent(tom, bob)."))
+        (list "atom" "punct" "atom" "punct" "atom" "punct" "punct" "eof"))
+      (dl-tk-test!
+        "rule shape"
+        (dl-tk-types (dl-tokenize "p(X) :- q(X)."))
+        (list
+          "atom"
+          "punct"
+          "var"
+          "punct"
+          "op"
+          "atom"
+          "punct"
+          "var"
+          "punct"
+          "punct"
+          "eof"))
+      (dl-tk-test!
+        "comparison literal"
+        (dl-tk-values (dl-tokenize "<(X, 5)"))
+        (list "<" "(" "X" "," 5 ")" nil))
+      (dl-tk-test!
+        "is form"
+        (dl-tk-values (dl-tokenize "is(Y, +(X, 1))"))
+        (list "is" "(" "Y" "," "+" "(" "X" "," 1 ")" ")" nil))
+      (dl-tk-test!
+        "line comment"
+        (dl-tk-types (dl-tokenize "% comment line\nfoo."))
+        (list "atom" "punct" "eof"))
+      (dl-tk-test!
+        "block comment"
+        (dl-tk-types (dl-tokenize "/* a\nb */ x."))
+        (list "atom" "punct" "eof"))
+      ;; Unexpected characters surface at tokenize time rather
+      ;; than being silently consumed (previously `?(X)` parsed as
+      ;; if the leading `?` weren't there).
+      (dl-tk-test!
+        "unexpected char raises"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-tokenize "?(X)"))
+            threw))
+        true)
+
+      ;; Unterminated string / quoted-atom must raise.
+      (dl-tk-test!
+        "unterminated string raises"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-tokenize "\"unclosed"))
+            threw))
+        true)
+
+      (dl-tk-test!
+        "unterminated quoted atom raises"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-tokenize "'unclosed"))
+            threw))
+        true)
+
+      ;; Unterminated block comment must raise — previously it was
+      ;; silently consumed to EOF.
+      (dl-tk-test!
+        "unterminated block comment raises"
+        (let ((threw false))
+          (do
+            (guard (e (#t (set! threw true)))
+              (dl-tokenize "/* unclosed comment"))
+            threw))
+        true)
+      (dl-tk-test!
+        "whitespace"
+        (dl-tk-types (dl-tokenize "  foo  ,\t bar  ."))
+        (list "atom" "punct" "atom" "punct" "eof"))
+      (dl-tk-test!
+        "positions"
+        (map (fn (t) (get t :pos)) (dl-tokenize "foo bar"))
+        (list 0 4 7)))))
+
+(define
+  dl-tokenize-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-tk-pass 0)
+      (set! dl-tk-fail 0)
+      (set! dl-tk-failures (list))
+      (dl-tk-run-all!)
+      {:failures dl-tk-failures :total (+ dl-tk-pass dl-tk-fail) :passed dl-tk-pass :failed dl-tk-fail})))

lib/datalog/tests/unify.sx

@@ -0,0 +1,194 @@
+;; lib/datalog/tests/unify.sx — unification + substitution tests.
+
+(define dl-ut-pass 0)
+(define dl-ut-fail 0)
+(define dl-ut-failures (list))
+
+(define
+  dl-ut-deep-equal?
+  (fn
+    (a b)
+    (cond
+      ((and (list? a) (list? b))
+        (and (= (len a) (len b)) (dl-ut-deq-list? a b 0)))
+      ((and (dict? a) (dict? b))
+        (let
+          ((ka (keys a)) (kb (keys b)))
+          (and (= (len ka) (len kb)) (dl-ut-deq-dict? a b ka 0))))
+      ((and (number? a) (number? b)) (= a b))
+      (else (equal? a b)))))
+
+(define
+  dl-ut-deq-list?
+  (fn
+    (a b i)
+    (cond
+      ((>= i (len a)) true)
+      ((not (dl-ut-deep-equal? (nth a i) (nth b i))) false)
+      (else (dl-ut-deq-list? a b (+ i 1))))))
+
+(define
+  dl-ut-deq-dict?
+  (fn
+    (a b ka i)
+    (cond
+      ((>= i (len ka)) true)
+      ((let ((k (nth ka i))) (not (dl-ut-deep-equal? (get a k) (get b k))))
+        false)
+      (else (dl-ut-deq-dict? a b ka (+ i 1))))))
+
+(define
+  dl-ut-test!
+  (fn
+    (name got expected)
+    (if
+      (dl-ut-deep-equal? got expected)
+      (set! dl-ut-pass (+ dl-ut-pass 1))
+      (do
+        (set! dl-ut-fail (+ dl-ut-fail 1))
+        (append!
+          dl-ut-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define
+  dl-ut-run-all!
+  (fn
+    ()
+    (do
+      (dl-ut-test! "var? uppercase" (dl-var? (quote X)) true)
+      (dl-ut-test! "var? underscore" (dl-var? (quote _foo)) true)
+      (dl-ut-test! "var? lowercase" (dl-var? (quote tom)) false)
+      (dl-ut-test! "var? number" (dl-var? 5) false)
+      (dl-ut-test! "var? string" (dl-var? "hi") false)
+      (dl-ut-test! "var? list" (dl-var? (list 1)) false)
+      (dl-ut-test!
+        "atom-atom match"
+        (dl-unify (quote tom) (quote tom) (dl-empty-subst))
+        {})
+      (dl-ut-test!
+        "atom-atom fail"
+        (dl-unify (quote tom) (quote bob) (dl-empty-subst))
+        nil)
+      (dl-ut-test!
+        "num-num match"
+        (dl-unify 5 5 (dl-empty-subst))
+        {})
+      (dl-ut-test!
+        "num-num fail"
+        (dl-unify 5 6 (dl-empty-subst))
+        nil)
+      (dl-ut-test!
+        "string match"
+        (dl-unify "hi" "hi" (dl-empty-subst))
+        {})
+      (dl-ut-test! "string fail" (dl-unify "hi" "bye" (dl-empty-subst)) nil)
+      (dl-ut-test!
+        "var-atom binds"
+        (dl-unify (quote X) (quote tom) (dl-empty-subst))
+        {:X (quote tom)})
+      (dl-ut-test!
+        "atom-var binds"
+        (dl-unify (quote tom) (quote X) (dl-empty-subst))
+        {:X (quote tom)})
+      (dl-ut-test!
+        "var-var same"
+        (dl-unify (quote X) (quote X) (dl-empty-subst))
+        {})
+      (dl-ut-test!
+        "var-var bind"
+        (let
+          ((s (dl-unify (quote X) (quote Y) (dl-empty-subst))))
+          (dl-walk (quote X) s))
+        (quote Y))
+      (dl-ut-test!
+        "tuple match"
+        (dl-unify
+          (list (quote parent) (quote X) (quote bob))
+          (list (quote parent) (quote tom) (quote Y))
+          (dl-empty-subst))
+        {:X (quote tom) :Y (quote bob)})
+      (dl-ut-test!
+        "tuple arity mismatch"
+        (dl-unify
+          (list (quote p) (quote X))
+          (list (quote p) (quote a) (quote b))
+          (dl-empty-subst))
+        nil)
+      (dl-ut-test!
+        "tuple head mismatch"
+        (dl-unify
+          (list (quote p) (quote X))
+          (list (quote q) (quote X))
+          (dl-empty-subst))
+        nil)
+      (dl-ut-test!
+        "walk chain"
+        (let
+          ((s1 (dl-unify (quote X) (quote Y) (dl-empty-subst))))
+          (let
+            ((s2 (dl-unify (quote Y) (quote tom) s1)))
+            (dl-walk (quote X) s2)))
+        (quote tom))
+
+      ;; Walk with circular substitution must not infinite-loop.
+      ;; Cycles return the current term unchanged.
+      (dl-ut-test!
+        "walk circular subst no hang"
+        (let ((s (dl-bind (quote B) (quote A)
+                   (dl-bind (quote A) (quote B) (dl-empty-subst)))))
+          (dl-walk (quote A) s))
+        (quote A))
+      (dl-ut-test!
+        "apply subst on tuple"
+        (let
+          ((s (dl-bind (quote X) (quote tom) (dl-empty-subst))))
+          (dl-apply-subst (list (quote parent) (quote X) (quote Y)) s))
+        (list (quote parent) (quote tom) (quote Y)))
+      (dl-ut-test!
+        "ground? all const"
+        (dl-ground?
+          (list (quote p) (quote tom) 5)
+          (dl-empty-subst))
+        true)
+      (dl-ut-test!
+        "ground? unbound var"
+        (dl-ground? (list (quote p) (quote X)) (dl-empty-subst))
+        false)
+      (dl-ut-test!
+        "ground? bound var"
+        (let
+          ((s (dl-bind (quote X) (quote tom) (dl-empty-subst))))
+          (dl-ground? (list (quote p) (quote X)) s))
+        true)
+      (dl-ut-test!
+        "ground? bare var"
+        (dl-ground? (quote X) (dl-empty-subst))
+        false)
+      (dl-ut-test!
+        "vars-of basic"
+        (dl-vars-of
+          (list (quote p) (quote X) (quote tom) (quote Y) (quote X)))
+        (list "X" "Y"))
+      (dl-ut-test!
+        "vars-of ground"
+        (dl-vars-of (list (quote p) (quote tom) (quote bob)))
+        (list))
+      (dl-ut-test!
+        "vars-of nested compound"
+        (dl-vars-of
+          (list
+            (quote is)
+            (quote Z)
+            (list (string->symbol "+") (quote X) 1)))
+        (list "Z" "X")))))
+
+(define
+  dl-unify-tests-run!
+  (fn
+    ()
+    (do
+      (set! dl-ut-pass 0)
+      (set! dl-ut-fail 0)
+      (set! dl-ut-failures (list))
+      (dl-ut-run-all!)
+      {:failures dl-ut-failures :total (+ dl-ut-pass dl-ut-fail) :passed dl-ut-pass :failed dl-ut-fail})))

lib/datalog/tokenizer.sx

@@ -0,0 +1,269 @@
+;; lib/datalog/tokenizer.sx — Datalog source → token stream
+;;
+;; Tokens: {:type T :value V :pos P}
+;; Types:
+;;   "atom"    — lowercase-start bare identifier
+;;   "var"     — uppercase-start or _-start ident (value is the name)
+;;   "number"  — numeric literal (decoded to number)
+;;   "string"  — "..." string literal OR quoted 'atom' (treated as a
+;;               string value to avoid the var-vs-atom ambiguity that
+;;               would arise from a quoted atom whose name starts with
+;;               an uppercase letter or underscore)
+;;   "punct"   — ( ) , .
+;;   "op"      — :- ?- <= >= != < > = + - * /
+;;   "eof"
+;;
+;; Datalog has no function symbols in arg position; the parser still
+;; accepts nested compounds for arithmetic ((is X (+ A B))) but safety
+;; analysis rejects non-arithmetic nesting at rule-load time.
+
+(define dl-make-token (fn (type value pos) {:type type :value value :pos pos}))
+
+(define dl-digit? (fn (c) (and (>= c "0") (<= c "9"))))
+(define dl-lower? (fn (c) (and (>= c "a") (<= c "z"))))
+(define dl-upper? (fn (c) (and (>= c "A") (<= c "Z"))))
+
+(define
+  dl-ident-char?
+  (fn (c) (or (dl-lower? c) (dl-upper? c) (dl-digit? c) (= c "_"))))
+
+(define dl-ws? (fn (c) (or (= c " ") (= c "\t") (= c "\n") (= c "\r"))))
+
+(define
+  dl-tokenize
+  (fn
+    (src)
+    (let
+      ((tokens (list)) (pos 0) (src-len (len src)))
+      (define
+        dl-peek
+        (fn
+          (offset)
+          (if (< (+ pos offset) src-len) (nth src (+ pos offset)) nil)))
+      (define cur (fn () (dl-peek 0)))
+      (define advance! (fn (n) (set! pos (+ pos n))))
+      (define
+        at?
+        (fn
+          (s)
+          (let
+            ((sl (len s)))
+            (and (<= (+ pos sl) src-len) (= (slice src pos (+ pos sl)) s)))))
+      (define
+        dl-emit!
+        (fn
+          (type value start)
+          (append! tokens (dl-make-token type value start))))
+      (define
+        skip-line-comment!
+        (fn
+          ()
+          (when
+            (and (< pos src-len) (not (= (cur) "\n")))
+            (do (advance! 1) (skip-line-comment!)))))
+      (define
+        skip-block-comment!
+        (fn
+          ()
+          (cond
+            ((>= pos src-len)
+              (error (str "Tokenizer: unterminated block comment "
+                          "(started at position " pos ")")))
+            ((and (= (cur) "*") (< (+ pos 1) src-len) (= (dl-peek 1) "/"))
+              (advance! 2))
+            (else (do (advance! 1) (skip-block-comment!))))))
+      (define
+        skip-ws!
+        (fn
+          ()
+          (cond
+            ((>= pos src-len) nil)
+            ((dl-ws? (cur)) (do (advance! 1) (skip-ws!)))
+            ((= (cur) "%")
+              (do (advance! 1) (skip-line-comment!) (skip-ws!)))
+            ((and (= (cur) "/") (< (+ pos 1) src-len) (= (dl-peek 1) "*"))
+              (do (advance! 2) (skip-block-comment!) (skip-ws!)))
+            (else nil))))
+      (define
+        read-ident
+        (fn
+          (start)
+          (do
+            (when
+              (and (< pos src-len) (dl-ident-char? (cur)))
+              (do (advance! 1) (read-ident start)))
+            (slice src start pos))))
+      (define
+        read-decimal-digits!
+        (fn
+          ()
+          (when
+            (and (< pos src-len) (dl-digit? (cur)))
+            (do (advance! 1) (read-decimal-digits!)))))
+      (define
+        read-number
+        (fn
+          (start)
+          (do
+            (read-decimal-digits!)
+            (when
+              (and
+                (< pos src-len)
+                (= (cur) ".")
+                (< (+ pos 1) src-len)
+                (dl-digit? (dl-peek 1)))
+              (do (advance! 1) (read-decimal-digits!)))
+            (parse-number (slice src start pos)))))
+      (define
+        read-quoted
+        (fn
+          (quote-char)
+          (let
+            ((chars (list)))
+            (advance! 1)
+            (define
+              loop
+              (fn
+                ()
+                (cond
+                  ((>= pos src-len)
+                    (error
+                      (str "Tokenizer: unterminated "
+                           (if (= quote-char "'") "quoted atom" "string")
+                           " (started near position " pos ")")))
+                  ((= (cur) "\\")
+                    (do
+                      (advance! 1)
+                      (when
+                        (< pos src-len)
+                        (let
+                          ((ch (cur)))
+                          (do
+                            (cond
+                              ((= ch "n") (append! chars "\n"))
+                              ((= ch "t") (append! chars "\t"))
+                              ((= ch "r") (append! chars "\r"))
+                              ((= ch "\\") (append! chars "\\"))
+                              ((= ch "'") (append! chars "'"))
+                              ((= ch "\"") (append! chars "\""))
+                              (else (append! chars ch)))
+                            (advance! 1))))
+                      (loop)))
+                  ((= (cur) quote-char) (advance! 1))
+                  (else
+                    (do (append! chars (cur)) (advance! 1) (loop))))))
+            (loop)
+            (join "" chars))))
+      (define
+        scan!
+        (fn
+          ()
+          (do
+            (skip-ws!)
+            (when
+              (< pos src-len)
+              (let
+                ((ch (cur)) (start pos))
+                (cond
+                  ((at? ":-")
+                    (do
+                      (dl-emit! "op" ":-" start)
+                      (advance! 2)
+                      (scan!)))
+                  ((at? "?-")
+                    (do
+                      (dl-emit! "op" "?-" start)
+                      (advance! 2)
+                      (scan!)))
+                  ((at? "<=")
+                    (do
+                      (dl-emit! "op" "<=" start)
+                      (advance! 2)
+                      (scan!)))
+                  ((at? ">=")
+                    (do
+                      (dl-emit! "op" ">=" start)
+                      (advance! 2)
+                      (scan!)))
+                  ((at? "!=")
+                    (do
+                      (dl-emit! "op" "!=" start)
+                      (advance! 2)
+                      (scan!)))
+                  ((dl-digit? ch)
+                    (do
+                      (dl-emit! "number" (read-number start) start)
+                      (scan!)))
+                  ((= ch "'")
+                    ;; Quoted 'atoms' tokenize as strings so a name
+                    ;; like 'Hello World' doesn't get misclassified
+                    ;; as a variable by dl-var? (which inspects the
+                    ;; symbol's first character).
+                    (do (dl-emit! "string" (read-quoted "'") start) (scan!)))
+                  ((= ch "\"")
+                    (do (dl-emit! "string" (read-quoted "\"") start) (scan!)))
+                  ((dl-lower? ch)
+                    (do (dl-emit! "atom" (read-ident start) start) (scan!)))
+                  ((or (dl-upper? ch) (= ch "_"))
+                    (do (dl-emit! "var" (read-ident start) start) (scan!)))
+                  ((= ch "(")
+                    (do
+                      (dl-emit! "punct" "(" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch ")")
+                    (do
+                      (dl-emit! "punct" ")" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch ",")
+                    (do
+                      (dl-emit! "punct" "," start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch ".")
+                    (do
+                      (dl-emit! "punct" "." start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "<")
+                    (do
+                      (dl-emit! "op" "<" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch ">")
+                    (do
+                      (dl-emit! "op" ">" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "=")
+                    (do
+                      (dl-emit! "op" "=" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "+")
+                    (do
+                      (dl-emit! "op" "+" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "-")
+                    (do
+                      (dl-emit! "op" "-" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "*")
+                    (do
+                      (dl-emit! "op" "*" start)
+                      (advance! 1)
+                      (scan!)))
+                  ((= ch "/")
+                    (do
+                      (dl-emit! "op" "/" start)
+                      (advance! 1)
+                      (scan!)))
+                  (else (error
+                          (str "Tokenizer: unexpected character '" ch
+                               "' at position " start)))))))))
+      (scan!)
+      (dl-emit! "eof" nil pos)
+      tokens)))

lib/datalog/unify.sx

@@ -0,0 +1,171 @@
+;; lib/datalog/unify.sx — unification + substitution for Datalog terms.
+;;
+;; Term taxonomy (after parsing):
+;;   variable  — SX symbol whose first char is uppercase A–Z or '_'.
+;;   constant  — SX symbol whose first char is lowercase a–z (atom name).
+;;   number    — numeric literal.
+;;   string    — string literal.
+;;   compound  — SX list (functor arg ... arg). In core Datalog these
+;;               only appear as arithmetic expressions (see Phase 4
+;;               safety analysis); compound-against-compound unification
+;;               is supported anyway for completeness.
+;;
+;; Substitutions are immutable dicts keyed by variable name (string).
+;; A failed unification returns nil; success returns the extended subst.
+
+(define dl-empty-subst (fn () {}))
+
+(define
+  dl-var?
+  (fn
+    (term)
+    (and
+      (symbol? term)
+      (let
+        ((name (symbol->string term)))
+        (and
+          (> (len name) 0)
+          (let
+            ((c (slice name 0 1)))
+            (or (and (>= c "A") (<= c "Z")) (= c "_"))))))))
+
+;; Walk: chase variable bindings until we hit a non-variable or an unbound
+;; variable. The result is either a non-variable term or an unbound var.
+(define
+  dl-walk
+  (fn (term subst) (dl-walk-aux term subst (list))))
+
+;; Internal: walk with a visited-var set so circular substitutions
+;; (from raw dl-bind misuse) don't infinite-loop. Cycles return the
+;; current term unchanged.
+(define
+  dl-walk-aux
+  (fn
+    (term subst visited)
+    (if
+      (dl-var? term)
+      (let
+        ((name (symbol->string term)))
+        (cond
+          ((dl-member? name visited) term)
+          ((and (dict? subst) (has-key? subst name))
+            (let ((seen (list)))
+              (do
+                (for-each (fn (v) (append! seen v)) visited)
+                (append! seen name)
+                (dl-walk-aux (get subst name) subst seen))))
+          (else term)))
+      term)))
+
+;; Bind a variable symbol to a value in subst, returning a new subst.
+(define
+  dl-bind
+  (fn (var-sym value subst) (assoc subst (symbol->string var-sym) value)))
+
+(define
+  dl-unify
+  (fn
+    (t1 t2 subst)
+    (if
+      (nil? subst)
+      nil
+      (let
+        ((u1 (dl-walk t1 subst)) (u2 (dl-walk t2 subst)))
+        (cond
+          ((dl-var? u1)
+            (cond
+              ((and (dl-var? u2) (= (symbol->string u1) (symbol->string u2)))
+                subst)
+              (else (dl-bind u1 u2 subst))))
+          ((dl-var? u2) (dl-bind u2 u1 subst))
+          ((and (list? u1) (list? u2))
+            (if
+              (= (len u1) (len u2))
+              (dl-unify-list u1 u2 subst 0)
+              nil))
+          ((and (number? u1) (number? u2)) (if (= u1 u2) subst nil))
+          ((and (string? u1) (string? u2)) (if (= u1 u2) subst nil))
+          ((and (symbol? u1) (symbol? u2))
+            (if (= (symbol->string u1) (symbol->string u2)) subst nil))
+          (else nil))))))
+
+(define
+  dl-unify-list
+  (fn
+    (a b subst i)
+    (cond
+      ((nil? subst) nil)
+      ((>= i (len a)) subst)
+      (else
+        (dl-unify-list
+          a
+          b
+          (dl-unify (nth a i) (nth b i) subst)
+          (+ i 1))))))
+
+;; Apply substitution: walk the term and recurse into lists.
+(define
+  dl-apply-subst
+  (fn
+    (term subst)
+    (let
+      ((w (dl-walk term subst)))
+      (if (list? w) (map (fn (x) (dl-apply-subst x subst)) w) w))))
+
+;; Ground? — true iff no free variables remain after walking.
+(define
+  dl-ground?
+  (fn
+    (term subst)
+    (let
+      ((w (dl-walk term subst)))
+      (cond
+        ((dl-var? w) false)
+        ((list? w) (dl-ground-list? w subst 0))
+        (else true)))))
+
+(define
+  dl-ground-list?
+  (fn
+    (xs subst i)
+    (cond
+      ((>= i (len xs)) true)
+      ((not (dl-ground? (nth xs i) subst)) false)
+      (else (dl-ground-list? xs subst (+ i 1))))))
+
+;; Return the list of variable names appearing in a term (deduped, in
+;; left-to-right order). Useful for safety analysis later.
+(define
+  dl-vars-of
+  (fn (term) (let ((seen (list))) (do (dl-vars-of-aux term seen) seen))))
+
+(define
+  dl-vars-of-aux
+  (fn
+    (term acc)
+    (cond
+      ((dl-var? term)
+        (let
+          ((name (symbol->string term)))
+          (when (not (dl-member? name acc)) (append! acc name))))
+      ((list? term) (dl-vars-of-list term acc 0))
+      (else nil))))
+
+(define
+  dl-vars-of-list
+  (fn
+    (xs acc i)
+    (when
+      (< i (len xs))
+      (do
+        (dl-vars-of-aux (nth xs i) acc)
+        (dl-vars-of-list xs acc (+ i 1))))))
+
+(define
+  dl-member?
+  (fn
+    (x xs)
+    (cond
+      ((= (len xs) 0) false)
+      ((= (first xs) x) true)
+      (else (dl-member? x (rest xs))))))

lib/ocaml/baseline/abundant.ml

@@ -1,23 +0,0 @@
-let div_sum n =
-  let s = ref 1 in
-  let i = ref 2 in
-  while !i * !i <= n do
-    if n mod !i = 0 then begin
-      s := !s + !i;
-      let q = n / !i in
-      if q <> !i then s := !s + q
-    end;
-    i := !i + 1
-  done;
-  if n = 1 then 0 else !s
-
-let count_abundant n =
-  let c = ref 0 in
-  for i = 12 to n - 1 do
-    if div_sum i > i then c := !c + 1
-  done;
-  !c
-
-;;
-
-count_abundant 100

lib/ocaml/baseline/ackermann.ml

@@ -1,8 +0,0 @@
-let rec ack m n =
-  if m = 0 then n + 1
-  else if n = 0 then ack (m - 1) 1
-  else ack (m - 1) (ack m (n - 1))
-
-;;
-
-ack 3 4

lib/ocaml/baseline/activity_select.ml

@@ -1,31 +0,0 @@
-let max_nonoverlap intervals =
-  let arr = Array.of_list intervals in
-  let n = Array.length arr in
-  let sorted = Array.make n (0, 0) in
-  for i = 0 to n - 1 do
-    sorted.(i) <- arr.(i)
-  done;
-  for i = 0 to n - 1 do
-    for j = 0 to n - 2 - i do
-      let (_, e1) = sorted.(j) in
-      let (_, e2) = sorted.(j + 1) in
-      if e1 > e2 then begin
-        let t = sorted.(j) in
-        sorted.(j) <- sorted.(j + 1);
-        sorted.(j + 1) <- t
-      end
-    done
-  done;
-  let count = ref 0 in
-  let last_end = ref (-1000000) in
-  for i = 0 to n - 1 do
-    let (s, e) = sorted.(i) in
-    if s >= !last_end then begin
-      count := !count + 1;
-      last_end := e
-    end
-  done;
-  !count
-;;
-
-max_nonoverlap [(1, 4); (3, 5); (0, 6); (5, 7); (3, 8); (5, 9); (6, 10); (8, 11); (8, 12); (2, 13); (12, 14)]

lib/ocaml/baseline/adler32.ml

@@ -1,13 +0,0 @@
-let adler32 s =
-  let a = ref 1 in
-  let b = ref 0 in
-  let m = 65521 in
-  for i = 0 to String.length s - 1 do
-    a := (!a + Char.code s.[i]) mod m;
-    b := (!b + !a) mod m
-  done;
-  !b * 65536 + !a
-
-;;
-
-adler32 "Wikipedia"

lib/ocaml/baseline/anagram_check.ml

@@ -1,23 +0,0 @@
-let to_counts s =
-  let counts = Array.make 256 0 in
-  for i = 0 to String.length s - 1 do
-    let c = Char.code s.[i] in
-    counts.(c) <- counts.(c) + 1
-  done;
-  counts
-
-let same_counts a b =
-  let result = ref true in
-  for i = 0 to 255 do
-    if a.(i) <> b.(i) then result := false
-  done;
-  !result
-
-let is_anagram s t = same_counts (to_counts s) (to_counts t)
-
-;;
-
-(if is_anagram "listen" "silent" then 1 else 0) +
-(if is_anagram "hello" "world" then 1 else 0) +
-(if is_anagram "anagram" "nagaram" then 1 else 0) +
-(if is_anagram "abc" "abcd" then 1 else 0)

lib/ocaml/baseline/anagram_groups.ml

@@ -1,29 +0,0 @@
-let canonical s =
-  let chars = Array.make 26 0 in
-  for i = 0 to String.length s - 1 do
-    let k = Char.code s.[i] - Char.code 'a' in
-    if k >= 0 && k < 26 then chars.(k) <- chars.(k) + 1
-  done;
-  let buf = Buffer.create 26 in
-  for i = 0 to 25 do
-    for _ = 1 to chars.(i) do
-      Buffer.add_string buf (String.make 1 (Char.chr (i + Char.code 'a')))
-    done
-  done;
-  Buffer.contents buf
-
-let group_anagrams xs =
-  let h = Hashtbl.create 8 in
-  List.iter (fun s ->
-    let k = canonical s in
-    let cur = match Hashtbl.find_opt h k with
-              | Some xs -> xs
-              | None -> []
-    in
-    Hashtbl.replace h k (s :: cur)
-  ) xs;
-  Hashtbl.length h
-
-;;
-
-group_anagrams ["eat"; "tea"; "tan"; "ate"; "nat"; "bat"]

lib/ocaml/baseline/anagrams.ml

@@ -1,26 +0,0 @@
-(* Baseline: count anagram groups using Hashtbl + sort *)
-
-(* Sort the chars in a string to get its anagram-equivalence key *)
-let canonical s =
-  let n = String.length s in
-  let chars = ref [] in
-  for i = 0 to n - 1 do
-    chars := (String.get s i) :: !chars
-  done ;
-  let sorted = List.sort compare !chars in
-  String.concat "" sorted
-;;
-
-let count_groups words =
-  let counts = Hashtbl.create 16 in
-  List.iter
-    (fun w ->
-      let k = canonical w in
-      match Hashtbl.find_opt counts k with
-      | None -> Hashtbl.add counts k 1
-      | Some n -> Hashtbl.replace counts k (n + 1))
-    words ;
-  Hashtbl.length counts
-;;
-
-count_groups ["eat"; "tea"; "tan"; "ate"; "nat"; "bat"]

lib/ocaml/baseline/atm.ml

@@ -1,17 +0,0 @@
-type account = { mutable balance : int }
-
-exception Insufficient
-
-let withdraw acct amt =
-  if amt > acct.balance then raise Insufficient
-  else acct.balance <- acct.balance - amt
-
-let deposit acct amt = acct.balance <- acct.balance + amt
-
-;;
-
-let a = { balance = 100 } in
-deposit a 50;
-withdraw a 30;
-try (withdraw a 200; -1)
-with Insufficient -> a.balance

lib/ocaml/baseline/bag.ml

@@ -1,18 +0,0 @@
-let count_words text =
-  let words = String.split_on_char ' ' text in
-  let counts = Hashtbl.create 8 in
-  List.iter (fun w ->
-    let n = match Hashtbl.find_opt counts w with
-            | Some n -> n + 1
-            | None -> 1
-    in
-    Hashtbl.replace counts w n
-  ) words;
-  counts
-
-let max_count counts =
-  Hashtbl.fold (fun _ v acc -> if v > acc then v else acc) counts 0
-
-;;
-
-max_count (count_words "the quick brown fox jumps over the lazy dog the fox")

lib/ocaml/baseline/balance.ml

@@ -1,25 +0,0 @@
-let is_balanced s =
-  let stack = Stack.create () in
-  let n = String.length s in
-  let ok = ref true in
-  let i = ref 0 in
-  while !i < n && !ok do
-    let c = s.[!i] in
-    (if c = '(' || c = '[' || c = '{' then Stack.push c stack
-     else if c = ')' then
-       (if Stack.is_empty stack || Stack.pop stack <> '(' then ok := false)
-     else if c = ']' then
-       (if Stack.is_empty stack || Stack.pop stack <> '[' then ok := false)
-     else if c = '}' then
-       (if Stack.is_empty stack || Stack.pop stack <> '{' then ok := false));
-    i := !i + 1
-  done;
-  !ok && Stack.is_empty stack
-
-;;
-
-(if is_balanced "({[abc]d}e)" then 1 else 0) +
-(if is_balanced "(a]" then 1 else 0) +
-(if is_balanced "{[}]" then 1 else 0) +
-(if is_balanced "(())" then 1 else 0) +
-(if is_balanced "" then 1 else 0)

lib/ocaml/baseline/base_n.ml

@@ -1,19 +0,0 @@
-let to_base_n n base =
-  let digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" in
-  if n = 0 then "0"
-  else begin
-    let m = ref (abs n) in
-    let acc = ref "" in
-    while !m > 0 do
-      acc := String.make 1 digits.[!m mod base] ^ !acc;
-      m := !m / base
-    done;
-    if n < 0 then "-" ^ !acc else !acc
-  end
-
-;;
-
-String.length (to_base_n 255 16) +
-String.length (to_base_n 1024 2) +
-String.length (to_base_n 100 10) +
-String.length (to_base_n 0 16)

lib/ocaml/baseline/bf_full.ml

@@ -1,42 +0,0 @@
-let interpret prog =
-  let mem = Array.make 256 0 in
-  let ptr = ref 0 in
-  let pc = ref 0 in
-  let n = String.length prog in
-  let acc = ref 0 in
-  while !pc < n do
-    let c = prog.[!pc] in
-    (if c = '>' then ptr := !ptr + 1
-     else if c = '<' then ptr := !ptr - 1
-     else if c = '+' then mem.(!ptr) <- mem.(!ptr) + 1
-     else if c = '-' then mem.(!ptr) <- mem.(!ptr) - 1
-     else if c = '.' then acc := !acc + mem.(!ptr)
-     else if c = '[' then begin
-       if mem.(!ptr) = 0 then begin
-         let depth = ref 1 in
-         while !depth > 0 do
-           pc := !pc + 1;
-           let c = prog.[!pc] in
-           if c = '[' then depth := !depth + 1
-           else if c = ']' then depth := !depth - 1
-         done
-       end
-     end
-     else if c = ']' then begin
-       if mem.(!ptr) <> 0 then begin
-         let depth = ref 1 in
-         while !depth > 0 do
-           pc := !pc - 1;
-           let c = prog.[!pc] in
-           if c = ']' then depth := !depth + 1
-           else if c = '[' then depth := !depth - 1
-         done
-       end
-     end);
-    pc := !pc + 1
-  done;
-  !acc
-
-;;
-
-interpret "+++[.-]"

lib/ocaml/baseline/bfs.ml

@@ -1,43 +0,0 @@
-(* Baseline: graph BFS using Queue + Hashtbl visited set.
-   Returns the count of reachable nodes. *)
-
-(* Adjacency as an assoc list of (node, neighbors). *)
-let graph =
-  [ ("A", ["B"; "C"])
-  ; ("B", ["D"])
-  ; ("C", ["D"; "E"])
-  ; ("D", ["F"])
-  ; ("E", ["F"])
-  ; ("F", [])
-  ]
-;;
-
-let neighbors n =
-  match List.assoc_opt n graph with
-  | None -> []
-  | Some ns -> ns
-;;
-
-let bfs start =
-  let visited = Hashtbl.create 16 in
-  let q = Queue.create () in
-  Queue.push start q ;
-  Hashtbl.add visited start true ;
-  let rec loop () =
-    if Queue.is_empty q then ()
-    else
-      let v = Queue.pop q in
-      List.iter
-        (fun n ->
-          if not (Hashtbl.mem visited n) then begin
-            Hashtbl.add visited n true ;
-            Queue.push n q
-          end)
-        (neighbors v) ;
-      loop ()
-  in
-  loop () ;
-  Hashtbl.length visited
-;;
-
-bfs "A"

lib/ocaml/baseline/bfs_grid.ml

@@ -1,42 +0,0 @@
-let h = 5
-let w = 5
-
-let grid = [|
-  [| 0; 0; 1; 0; 0 |];
-  [| 1; 0; 1; 0; 1 |];
-  [| 0; 0; 0; 0; 0 |];
-  [| 0; 1; 1; 1; 0 |];
-  [| 0; 0; 0; 0; 0 |]
-|]
-
-let step dist q r c nr nc =
-  if nr >= 0 && nr < h && nc >= 0 && nc < w
-     && grid.(nr).(nc) = 0 && dist.(nr).(nc) = -1 then begin
-    dist.(nr).(nc) <- dist.(r).(c) + 1;
-    Queue.push (nr * 10 + nc) q
-  end
-
-let bfs sr sc tr tc =
-  let dist = Array.init h (fun _ -> Array.make w (-1)) in
-  let q = Queue.create () in
-  dist.(sr).(sc) <- 0;
-  Queue.push (sr * 10 + sc) q;
-  let go = ref true in
-  while !go do
-    if Queue.is_empty q then go := false
-    else if dist.(tr).(tc) <> -1 then go := false
-    else begin
-      let rc = Queue.pop q in
-      let r = rc / 10 in
-      let c = rc mod 10 in
-      step dist q r c (r - 1) c;
-      step dist q r c (r + 1) c;
-      step dist q r c r (c - 1);
-      step dist q r c r (c + 1)
-    end
-  done;
-  dist.(tr).(tc)
-
-;;
-
-bfs 0 0 4 4

lib/ocaml/baseline/bigint_add.ml

@@ -1,24 +0,0 @@
-let bigint_add a b =
-  let rec aux a b carry =
-    match (a, b) with
-    | ([], []) -> if carry = 0 then [] else [carry]
-    | (x :: xs, []) ->
-      let s = x + carry in
-      (s mod 10) :: aux xs [] (s / 10)
-    | ([], y :: ys) ->
-      let s = y + carry in
-      (s mod 10) :: aux [] ys (s / 10)
-    | (x :: xs, y :: ys) ->
-      let s = x + y + carry in
-      (s mod 10) :: aux xs ys (s / 10)
-  in
-  aux a b 0
-
-;;
-
-let r1 = bigint_add [9;9;9] [1] in
-let r2 = bigint_add [5;6;7] [8;9;1] in
-let r3 = bigint_add [9;9;9;9;9;9;9;9] [1] in
-List.fold_left (+) 0 r1
-  + List.fold_left (+) 0 r2
-  + List.length r3

lib/ocaml/baseline/binary_heap.ml

@@ -1,47 +0,0 @@
-let parent i = (i - 1) / 2
-let lchild i = 2 * i + 1
-let rchild i = 2 * i + 2
-
-let swap a i j =
-  let t = a.(i) in
-  a.(i) <- a.(j);
-  a.(j) <- t
-
-let rec sift_up a i =
-  if i > 0 && a.(parent i) > a.(i) then begin
-    swap a i (parent i);
-    sift_up a (parent i)
-  end
-
-let rec sift_down a n i =
-  let l = lchild i and r = rchild i in
-  let smallest = ref i in
-  if l < n && a.(l) < a.(!smallest) then smallest := l;
-  if r < n && a.(r) < a.(!smallest) then smallest := r;
-  if !smallest <> i then begin
-    swap a i !smallest;
-    sift_down a n !smallest
-  end
-
-let push a size x =
-  a.(!size) <- x;
-  size := !size + 1;
-  sift_up a (!size - 1)
-
-let pop a size =
-  let m = a.(0) in
-  size := !size - 1;
-  a.(0) <- a.(!size);
-  sift_down a !size 0;
-  m
-
-;;
-
-let a = Array.make 20 0 in
-let s = ref 0 in
-List.iter (fun x -> push a s x) [9; 4; 7; 1; 8; 3; 5; 2; 6];
-let total = ref 0 in
-for _ = 1 to 9 do
-  total := !total * 10 + pop a s
-done;
-!total

lib/ocaml/baseline/bipartite.ml

@@ -1,39 +0,0 @@
-let is_bipartite n adj =
-  let color = Array.make n (-1) in
-  let ok = ref true in
-  let q = Queue.create () in
-  for src = 0 to n - 1 do
-    if color.(src) = -1 then begin
-      color.(src) <- 0;
-      Queue.push src q;
-      while not (Queue.is_empty q) do
-        let u = Queue.pop q in
-        List.iter (fun v ->
-          if color.(v) = -1 then begin
-            color.(v) <- 1 - color.(u);
-            Queue.push v q
-          end else if color.(v) = color.(u) then
-            ok := false
-        ) adj.(u)
-      done
-    end
-  done;
-  let zeros = ref 0 in
-  for i = 0 to n - 1 do
-    if color.(i) = 0 then zeros := !zeros + 1
-  done;
-  if !ok then !zeros else -1
-
-;;
-
-let n = 7 in
-let adj = [|
-  [1; 3];
-  [0; 2; 4];
-  [1; 5];
-  [0; 4; 6];
-  [1; 3];
-  [2; 6];
-  [3; 5]
-|] in
-is_bipartite n adj

lib/ocaml/baseline/bisect.ml

@@ -1,13 +0,0 @@
-let bisect f lo hi =
-  let lo = ref lo and hi = ref hi in
-  for _ = 1 to 50 do
-    let mid = (!lo +. !hi) /. 2.0 in
-    if f mid = 0.0 || f !lo *. f mid < 0.0 then hi := mid
-    else lo := mid
-  done;
-  !lo
-
-;;
-
-let r = bisect (fun x -> x *. x -. 2.0) 1.0 2.0 in
-int_of_float (r *. 100.0)

lib/ocaml/baseline/bits.ml

@@ -1,12 +0,0 @@
-let popcount n =
-  let count = ref 0 in
-  let m = ref n in
-  while !m > 0 do
-    if !m land 1 = 1 then count := !count + 1;
-    m := !m lsr 1
-  done;
-  !count
-
-;;
-
-popcount 1023 + popcount 5 + popcount 1024 + popcount 0xff

lib/ocaml/baseline/bowling.ml

@@ -1,24 +0,0 @@
-let bowling_score frames =
-  let arr = Array.of_list frames in
-  let n = Array.length arr in
-  let total = ref 0 in
-  let i = ref 0 in
-  let frame = ref 1 in
-  while !frame <= 10 && !i < n do
-    if arr.(!i) = 10 then begin
-      total := !total + 10 + arr.(!i + 1) + arr.(!i + 2);
-      i := !i + 1
-    end else if !i + 1 < n && arr.(!i) + arr.(!i + 1) = 10 then begin
-      total := !total + 10 + arr.(!i + 2);
-      i := !i + 2
-    end else begin
-      total := !total + arr.(!i) + arr.(!i + 1);
-      i := !i + 2
-    end;
-    frame := !frame + 1
-  done;
-  !total
-
-;;
-
-bowling_score [10; 7; 3; 9; 0; 10; 0; 8; 8; 2; 0; 6; 10; 10; 10; 8; 1]

lib/ocaml/baseline/bracket_match.ml

@@ -1,32 +0,0 @@
-let bracket_match s =
-  let n = String.length s in
-  let stack = ref [] in
-  let ok = ref true in
-  let i = ref 0 in
-  while !ok && !i < n do
-    let c = s.[!i] in
-    if c = '(' || c = '[' || c = '{' then
-      stack := c :: !stack
-    else if c = ')' || c = ']' || c = '}' then begin
-      match !stack with
-      | [] -> ok := false
-      | top :: rest ->
-        let pair =
-          (c = ')' && top = '(') ||
-          (c = ']' && top = '[') ||
-          (c = '}' && top = '{')
-        in
-        if pair then stack := rest else ok := false
-    end;
-    i := !i + 1
-  done;
-  if !ok && !stack = [] then 1 else 0
-
-;;
-
-let strings = ["()"; "[{()}]"; "({[}])"; ""; "(("; "()[](){}"; "(a(b)c)"; "(()"; "])"] in
-let count = ref 0 in
-List.iter (fun s ->
-  count := !count + bracket_match s
-) strings;
-!count

lib/ocaml/baseline/brainfuck.ml

@@ -1,20 +0,0 @@
-let interpret prog =
-  let mem = Array.make 256 0 in
-  let ptr = ref 0 in
-  let pc = ref 0 in
-  let n = String.length prog in
-  let acc = ref 0 in
-  while !pc < n do
-    let c = prog.[!pc] in
-    (if c = '>' then ptr := !ptr + 1
-     else if c = '<' then ptr := !ptr - 1
-     else if c = '+' then mem.(!ptr) <- mem.(!ptr) + 1
-     else if c = '-' then mem.(!ptr) <- mem.(!ptr) - 1
-     else if c = '.' then acc := !acc + mem.(!ptr));
-    pc := !pc + 1
-  done;
-  !acc
-
-;;
-
-interpret "+++++.+++++.+++++.+++++.+++++."

lib/ocaml/baseline/bs_bounds.ml

@@ -1,27 +0,0 @@
-let lower_bound arr x =
-  let lo = ref 0 and hi = ref (Array.length arr) in
-  while !lo < !hi do
-    let mid = (!lo + !hi) / 2 in
-    if arr.(mid) < x then lo := mid + 1
-    else hi := mid
-  done;
-  !lo
-
-let upper_bound arr x =
-  let lo = ref 0 and hi = ref (Array.length arr) in
-  while !lo < !hi do
-    let mid = (!lo + !hi) / 2 in
-    if arr.(mid) <= x then lo := mid + 1
-    else hi := mid
-  done;
-  !lo
-
-;;
-
-let a = [| 1; 2; 2; 3; 3; 3; 5; 7; 9 |] in
-let cnt3 = upper_bound a 3 - lower_bound a 3 in
-let cnt2 = upper_bound a 2 - lower_bound a 2 in
-let cnt5 = upper_bound a 5 - lower_bound a 5 in
-let cnt9 = upper_bound a 9 - lower_bound a 9 in
-let cnt4 = upper_bound a 4 - lower_bound a 4 in
-cnt3 * 1000 + cnt2 * 100 + cnt5 * 10 + cnt9 + cnt4

lib/ocaml/baseline/bs_rotated.ml

@@ -1,25 +0,0 @@
-let bs_rotated arr target =
-  let lo = ref 0 in
-  let hi = ref (Array.length arr - 1) in
-  let result = ref (-1) in
-  while !lo <= !hi && !result = -1 do
-    let mid = (!lo + !hi) / 2 in
-    if arr.(mid) = target then result := mid
-    else if arr.(!lo) <= arr.(mid) then begin
-      if target >= arr.(!lo) && target < arr.(mid) then
-        hi := mid - 1
-      else
-        lo := mid + 1
-    end else begin
-      if target > arr.(mid) && target <= arr.(!hi) then
-        lo := mid + 1
-      else
-        hi := mid - 1
-    end
-  done;
-  !result
-
-;;
-
-let a = [| 4; 5; 6; 7; 0; 1; 2 |] in
-bs_rotated a 0 + bs_rotated a 7 * 10 + bs_rotated a 3 * 100

lib/ocaml/baseline/bsearch.ml

@@ -1,16 +0,0 @@
-let bsearch arr target =
-  let n = Array.length arr in
-  let lo = ref 0 and hi = ref (n - 1) in
-  let found = ref (-1) in
-  while !lo <= !hi && !found = -1 do
-    let mid = (!lo + !hi) / 2 in
-    if arr.(mid) = target then found := mid
-    else if arr.(mid) < target then lo := mid + 1
-    else hi := mid - 1
-  done;
-  !found
-
-;;
-
-let a = Array.of_list [1;3;5;7;9;11;13;15;17;19;21] in
-bsearch a 13 + bsearch a 5 + bsearch a 100

lib/ocaml/baseline/btree.ml

@@ -1,25 +0,0 @@
-(* Baseline: binary search tree with insert + in-order traversal *)
-type 'a tree =
-  | Leaf
-  | Node of 'a * 'a tree * 'a tree
-;;
-
-let rec insert x t =
-  match t with
-  | Leaf -> Node (x, Leaf, Leaf)
-  | Node (v, l, r) ->
-    if x < v then Node (v, insert x l, r)
-    else if x > v then Node (v, l, insert x r)
-    else t
-;;
-
-let rec inorder t =
-  match t with
-  | Leaf -> []
-  | Node (v, l, r) -> List.append (inorder l) (v :: inorder r)
-;;
-
-let from_list xs = List.fold_left (fun t x -> insert x t) Leaf xs ;;
-
-let t = from_list [5; 3; 8; 1; 4; 7; 9; 2] ;;
-List.fold_left (fun a b -> a + b) 0 (inorder t)

lib/ocaml/baseline/caesar.ml

@@ -1,14 +0,0 @@
-let shift_char c k =
-  let n = Char.code c in
-  if n >= 97 && n <= 122 then
-    Char.chr (((n - 97 + k) mod 26 + 26) mod 26 + 97)
-  else c
-
-let encode s k =
-  String.init (String.length s) (fun i -> shift_char s.[i] k)
-;;
-
-(* ROT13 round-trip: encode (encode "hello" 13) 13 = "hello".
-   Sum the codes of two chars to give a deterministic integer check. *)
-let r = encode (encode "hello" 13) 13 in
-Char.code r.[0] + Char.code r.[4]

lib/ocaml/baseline/calc.ml

@@ -1,76 +0,0 @@
-(* Baseline: recursive-descent calculator for "+", "*", parens, ints. *)
-type expr =
-  | Lit of int
-  | Add of expr * expr
-  | Mul of expr * expr
-;;
-
-let parse_input src =
-  let pos = ref 0 in
-  let peek () = if !pos < String.length src then String.get src !pos else "" in
-  let advance () = pos := !pos + 1 in
-  let skip_ws () =
-    while !pos < String.length src && peek () = " " do advance () done
-  in
-
-  let rec parse_atom () =
-    skip_ws () ;
-    if peek () = "(" then begin
-      advance () ;
-      let e = parse_expr () in
-      skip_ws () ;
-      advance () ; (* consume ')' *)
-      e
-    end
-    else
-      let start = !pos in
-      let rec digits () =
-        if !pos < String.length src then
-          let c = peek () in
-          if c >= "0" && c <= "9" then begin advance () ; digits () end
-          else ()
-      in
-      digits () ;
-      let n = Int.of_string (String.sub src start (!pos - start)) in
-      Lit n
-
-  and parse_term () =
-    skip_ws () ;
-    let lhs = ref (parse_atom ()) in
-    let rec loop () =
-      skip_ws () ;
-      if peek () = "*" then begin
-        advance () ;
-        lhs := Mul (!lhs, parse_atom ()) ;
-        loop ()
-      end
-    in
-    loop () ;
-    !lhs
-
-  and parse_expr () =
-    skip_ws () ;
-    let lhs = ref (parse_term ()) in
-    let rec loop () =
-      skip_ws () ;
-      if peek () = "+" then begin
-        advance () ;
-        lhs := Add (!lhs, parse_term ()) ;
-        loop ()
-      end
-    in
-    loop () ;
-    !lhs
-  in
-  parse_expr ()
-;;
-
-let rec eval e =
-  match e with
-  | Lit n -> n
-  | Add (a, b) -> eval a + eval b
-  | Mul (a, b) -> eval a * eval b
-;;
-
-(* (1 + 2) * 3 + 4 = 9 + 4 = 13 *)
-eval (parse_input "(1 + 2) * 3 + 4")

lib/ocaml/baseline/catalan.ml

@@ -1,13 +0,0 @@
-let catalan n =
-  let dp = Array.make (n + 1) 0 in
-  dp.(0) <- 1;
-  for i = 1 to n do
-    for j = 0 to i - 1 do
-      dp.(i) <- dp.(i) + dp.(j) * dp.(i - 1 - j)
-    done
-  done;
-  dp.(n)
-
-;;
-
-catalan 5

lib/ocaml/baseline/closures.ml

@@ -1,5 +0,0 @@
-(* Baseline: closures + curried application *)
-let make_adder n = fun x -> n + x ;;
-let add5 = make_adder 5 ;;
-let add10 = make_adder 10 ;;
-add5 100 + add10 200

lib/ocaml/baseline/coin_change.ml

@@ -1,15 +0,0 @@
-let coin_change coins target =
-  let dp = Array.make (target + 1) (target + 1) in
-  dp.(0) <- 0;
-  for i = 1 to target do
-    List.iter (fun c ->
-      if c <= i && dp.(i - c) + 1 < dp.(i) then
-        dp.(i) <- dp.(i - c) + 1
-    ) coins
-  done;
-  if dp.(target) > target then -1
-  else dp.(target)
-
-;;
-
-coin_change [1; 5; 10; 25] 67

lib/ocaml/baseline/coin_min.ml

@@ -1,16 +0,0 @@
-let coin_min coins amount =
-  let dp = Array.make (amount + 1) (-1) in
-  dp.(0) <- 0;
-  for i = 1 to amount do
-    List.iter (fun c ->
-      if c <= i && dp.(i - c) >= 0 then begin
-        let cand = dp.(i - c) + 1 in
-        if dp.(i) < 0 || cand < dp.(i) then dp.(i) <- cand
-      end
-    ) coins
-  done;
-  dp.(amount)
-
-;;
-
-coin_min [1; 5; 10; 25] 67

lib/ocaml/baseline/combinations.ml

@@ -1,12 +0,0 @@
-let rec choose k xs =
-  if k = 0 then [[]]
-  else
-    match xs with
-    | [] -> []
-    | h :: rest ->
-      List.map (fun c -> h :: c) (choose (k - 1) rest)
-      @ choose k rest
-
-;;
-
-List.length (choose 4 [1; 2; 3; 4; 5; 6; 7; 8; 9])

lib/ocaml/baseline/convex_hull.ml

@@ -1,43 +0,0 @@
-let cross ox oy ax ay bx by =
-  (ax - ox) * (by - oy) - (ay - oy) * (bx - ox)
-
-let hull_size pts =
-  let n = List.length pts in
-  if n < 3 then n
-  else begin
-    let sorted = List.sort (fun (a, b) (c, d) ->
-      if a <> c then compare a c else compare b d) pts in
-    let arr = Array.of_list sorted in
-    let h = Array.make (2 * n) (0, 0) in
-    let k = ref 0 in
-    for i = 0 to n - 1 do
-      let (xi, yi) = arr.(i) in
-      let cont = ref true in
-      while !cont && !k >= 2 do
-        let (ox, oy) = h.(!k - 2) in
-        let (ax, ay) = h.(!k - 1) in
-        if cross ox oy ax ay xi yi <= 0 then k := !k - 1
-        else cont := false
-      done;
-      h.(!k) <- (xi, yi);
-      k := !k + 1
-    done;
-    let lo = !k + 1 in
-    for i = n - 2 downto 0 do
-      let (xi, yi) = arr.(i) in
-      let cont = ref true in
-      while !cont && !k >= lo do
-        let (ox, oy) = h.(!k - 2) in
-        let (ax, ay) = h.(!k - 1) in
-        if cross ox oy ax ay xi yi <= 0 then k := !k - 1
-        else cont := false
-      done;
-      h.(!k) <- (xi, yi);
-      k := !k + 1
-    done;
-    !k - 1
-  end
-
-;;
-
-hull_size [(0, 0); (1, 1); (2, 0); (2, 2); (0, 2); (1, 0); (3, 3); (5, 1)]

lib/ocaml/baseline/count_bits.ml

@@ -1,14 +0,0 @@
-let count_bits n =
-  let result = Array.make (n + 1) 0 in
-  for i = 1 to n do
-    result.(i) <- result.(i / 2) + (i mod 2)
-  done;
-  let sum = ref 0 in
-  for i = 0 to n do
-    sum := !sum + result.(i)
-  done;
-  !sum
-
-;;
-
-count_bits 100

lib/ocaml/baseline/count_change.ml

@@ -1,13 +0,0 @@
-let count_ways coins target =
-  let dp = Array.make (target + 1) 0 in
-  dp.(0) <- 1;
-  List.iter (fun c ->
-    for i = c to target do
-      dp.(i) <- dp.(i) + dp.(i - c)
-    done
-  ) coins;
-  dp.(target)
-
-;;
-
-count_ways [1; 2; 5; 10; 25] 50

lib/ocaml/baseline/count_inversions.ml

@@ -1,42 +0,0 @@
-let count_inv arr =
-  let n = Array.length arr in
-  let temp = Array.make n 0 in
-  let count = ref 0 in
-  let rec merge lo mid hi =
-    let i = ref lo and j = ref (mid + 1) and k = ref lo in
-    while !i <= mid && !j <= hi do
-      if arr.(!i) <= arr.(!j) then begin
-        temp.(!k) <- arr.(!i);
-        i := !i + 1
-      end else begin
-        temp.(!k) <- arr.(!j);
-        count := !count + (mid - !i + 1);
-        j := !j + 1
-      end;
-      k := !k + 1
-    done;
-    while !i <= mid do
-      temp.(!k) <- arr.(!i);
-      i := !i + 1; k := !k + 1
-    done;
-    while !j <= hi do
-      temp.(!k) <- arr.(!j);
-      j := !j + 1; k := !k + 1
-    done;
-    for x = lo to hi do
-      arr.(x) <- temp.(x)
-    done
-  and sort lo hi =
-    if lo < hi then begin
-      let mid = (lo + hi) / 2 in
-      sort lo mid;
-      sort (mid + 1) hi;
-      merge lo mid hi
-    end
-  in
-  sort 0 (n - 1);
-  !count
-
-;;
-
-count_inv [|8; 4; 2; 1; 3; 5; 7; 6|]

lib/ocaml/baseline/count_palindromes.ml

@@ -1,17 +0,0 @@
-let count_pal s =
-  let n = String.length s in
-  let count = ref 0 in
-  for c = 0 to 2 * n - 2 do
-    let l = ref (c / 2) in
-    let r = ref ((c + 1) / 2) in
-    while !l >= 0 && !r < n && s.[!l] = s.[!r] do
-      count := !count + 1;
-      l := !l - 1;
-      r := !r + 1
-    done
-  done;
-  !count
-
-;;
-
-count_pal "aabaa"

lib/ocaml/baseline/count_paths_dag.ml

@@ -1,42 +0,0 @@
-let n = 6
-let adj = [|
-  [1; 2];
-  [3];
-  [3; 4];
-  [5];
-  [5];
-  []
-|]
-
-let in_deg = Array.make n 0
-let paths = Array.make n 0
-
-let count_paths () =
-  for u = 0 to n - 1 do
-    List.iter (fun v -> in_deg.(v) <- in_deg.(v) + 1) adj.(u)
-  done;
-  let order = ref [] in
-  let q = Queue.create () in
-  for v = 0 to n - 1 do
-    if in_deg.(v) = 0 then Queue.push v q
-  done;
-  while not (Queue.is_empty q) do
-    let u = Queue.pop q in
-    order := u :: !order;
-    List.iter (fun v ->
-      in_deg.(v) <- in_deg.(v) - 1;
-      if in_deg.(v) = 0 then Queue.push v q
-    ) adj.(u)
-  done;
-  paths.(0) <- 1;
-  let topo = List.rev !order in
-  List.iter (fun u ->
-    List.iter (fun v ->
-      paths.(v) <- paths.(v) + paths.(u)
-    ) adj.(u)
-  ) topo;
-  paths.(n - 1)
-
-;;
-
-count_paths ()

lib/ocaml/baseline/count_subarrays_k.ml

@@ -1,16 +0,0 @@
-let count_subarr_sum_k arr k =
-  let n = Array.length arr in
-  let prefix = Array.make (n + 1) 0 in
-  for i = 0 to n - 1 do
-    prefix.(i + 1) <- prefix.(i) + arr.(i)
-  done;
-  let count = ref 0 in
-  for i = 0 to n - 1 do
-    for j = i + 1 to n do
-      if prefix.(j) - prefix.(i) = k then count := !count + 1
-    done
-  done;
-  !count
-;;
-
-count_subarr_sum_k [| 1; 1; 1; 2; -1; 3; 1; -2; 4 |] 3

lib/ocaml/baseline/csv.ml

@@ -1,12 +0,0 @@
-let sum_second_col text =
-  let lines = String.split_on_char '\n' text in
-  List.fold_left (fun acc line ->
-    let fields = String.split_on_char ',' line in
-    if List.length fields >= 2 then
-      acc + int_of_string (List.nth fields 1)
-    else acc
-  ) 0 lines
-
-;;
-
-sum_second_col "a,1,extra\nb,2,extra\nc,3,extra\nd,4,extra"

lib/ocaml/baseline/daily_temperatures.ml

@@ -1,24 +0,0 @@
-let daily_temperatures temps =
-  let n = Array.length temps in
-  let answer = Array.make n 0 in
-  let stack = ref [] in
-  for i = 0 to n - 1 do
-    let cont = ref true in
-    while !cont do
-      match !stack with
-      | top :: rest when temps.(top) < temps.(i) ->
-        answer.(top) <- i - top;
-        stack := rest
-      | _ -> cont := false
-    done;
-    stack := i :: !stack
-  done;
-  let sum = ref 0 in
-  for i = 0 to n - 1 do
-    sum := !sum + answer.(i)
-  done;
-  !sum
-
-;;
-
-daily_temperatures [| 73; 74; 75; 71; 69; 72; 76; 73 |]

lib/ocaml/baseline/dijkstra.ml

@@ -1,37 +0,0 @@
-let n = 5
-
-let edges = [|
-  [(1, 4); (2, 1)];
-  [(3, 1)];
-  [(1, 2); (3, 5)];
-  [(4, 3)];
-  []
-|]
-
-let dijkstra src =
-  let dist = Array.make n 1000000 in
-  dist.(src) <- 0;
-  let visited = Array.make n false in
-  for _ = 0 to n - 1 do
-    let u = ref (-1) in
-    let best = ref 1000000 in
-    for v = 0 to n - 1 do
-      if (not visited.(v)) && dist.(v) < !best then begin
-        best := dist.(v);
-        u := v
-      end
-    done;
-    if !u >= 0 then begin
-      visited.(!u) <- true;
-      List.iter (fun (v, w) ->
-        if dist.(!u) + w < dist.(v) then
-          dist.(v) <- dist.(!u) + w
-      ) edges.(!u)
-    end
-  done;
-  dist
-
-;;
-
-let d = dijkstra 0 in
-d.(4)

lib/ocaml/baseline/distinct_subseq.ml

@@ -1,20 +0,0 @@
-let count_subseq s t =
-  let m = String.length s in
-  let n = String.length t in
-  let dp = Array.init (m + 1) (fun _ -> Array.make (n + 1) 0) in
-  for i = 0 to m do
-    dp.(i).(0) <- 1
-  done;
-  for i = 1 to m do
-    for j = 1 to n do
-      if s.[i - 1] = t.[j - 1] then
-        dp.(i).(j) <- dp.(i - 1).(j) + dp.(i - 1).(j - 1)
-      else
-        dp.(i).(j) <- dp.(i - 1).(j)
-    done
-  done;
-  dp.(m).(n)
-
-;;
-
-count_subseq "rabbbit" "rabbit"

lib/ocaml/baseline/dp_word_break.ml

@@ -1,27 +0,0 @@
-let word_break s words =
-  let n = String.length s in
-  let dp = Array.make (n + 1) false in
-  dp.(0) <- true;
-  for i = 1 to n do
-    List.iter (fun w ->
-      let wl = String.length w in
-      if i >= wl && dp.(i - wl) then begin
-        let prefix = String.sub s (i - wl) wl in
-        if prefix = w then dp.(i) <- true
-      end
-    ) words
-  done;
-  if dp.(n) then 1 else 0
-
-let count_ok strings words =
-  let count = ref 0 in
-  List.iter (fun s ->
-    count := !count + word_break s words
-  ) strings;
-  !count
-
-;;
-
-let dict = ["apple"; "pen"; "pine"; "pineapple"; "cats"; "cat"; "and"; "sand"; "dog"] in
-let inputs = ["applepenapple"; "pineapplepenapple"; "catsanddog"; "catsandog"; "applesand"] in
-count_ok inputs dict

lib/ocaml/baseline/egg_drop.ml

@@ -1,26 +0,0 @@
-let egg_drop eggs floors =
-  let dp = Array.init (eggs + 1) (fun _ -> Array.make (floors + 1) 0) in
-  for f = 1 to floors do
-    dp.(1).(f) <- f
-  done;
-  for e = 1 to eggs do
-    dp.(e).(0) <- 0;
-    dp.(e).(1) <- 1
-  done;
-  for e = 2 to eggs do
-    for f = 2 to floors do
-      let best = ref 100000000 in
-      for k = 1 to f do
-        let bre = dp.(e - 1).(k - 1) in
-        let sur = dp.(e).(f - k) in
-        let cand = 1 + (if bre > sur then bre else sur) in
-        if cand < !best then best := cand
-      done;
-      dp.(e).(f) <- !best
-    done
-  done;
-  dp.(eggs).(floors)
-
-;;
-
-egg_drop 2 36

lib/ocaml/baseline/euler1.ml

@@ -1,10 +0,0 @@
-let euler1 limit =
-  let sum = ref 0 in
-  for i = 1 to limit - 1 do
-    if i mod 3 = 0 || i mod 5 = 0 then sum := !sum + i
-  done;
-  !sum
-
-;;
-
-euler1 1000

lib/ocaml/baseline/euler10.ml

@@ -1,22 +0,0 @@
-let sieve_sum n =
-  let s = Array.make (n + 1) true in
-  s.(0) <- false;
-  s.(1) <- false;
-  for i = 2 to n do
-    if s.(i) then begin
-      let j = ref (i * i) in
-      while !j <= n do
-        s.(!j) <- false;
-        j := !j + i
-      done
-    end
-  done;
-  let total = ref 0 in
-  for i = 2 to n do
-    if s.(i) then total := !total + i
-  done;
-  !total
-
-;;
-
-sieve_sum 100

lib/ocaml/baseline/euler14.ml

@@ -1,25 +0,0 @@
-let collatz_len n =
-  let m = ref n in
-  let c = ref 0 in
-  while !m > 1 do
-    if !m mod 2 = 0 then m := !m / 2
-    else m := 3 * !m + 1;
-    c := !c + 1
-  done;
-  !c
-
-let euler14 limit =
-  let best = ref 0 in
-  let best_n = ref 0 in
-  for n = 2 to limit do
-    let l = collatz_len n in
-    if l > !best then begin
-      best := l;
-      best_n := n
-    end
-  done;
-  !best_n
-
-;;
-
-euler14 100

lib/ocaml/baseline/euler16.ml

@@ -1,14 +0,0 @@
-let euler16 n =
-  let p = ref 1 in
-  for _ = 1 to n do p := !p * 2 done;
-  let sum = ref 0 in
-  let m = ref !p in
-  while !m > 0 do
-    sum := !sum + !m mod 10;
-    m := !m / 10
-  done;
-  !sum
-
-;;
-
-euler16 15

lib/ocaml/baseline/euler2.ml

@@ -1,15 +0,0 @@
-let euler2 limit =
-  let a = ref 1 in
-  let b = ref 2 in
-  let sum = ref 0 in
-  while !a <= limit do
-    if !a mod 2 = 0 then sum := !sum + !a;
-    let c = !a + !b in
-    a := !b;
-    b := c
-  done;
-  !sum
-
-;;
-
-euler2 4000000

lib/ocaml/baseline/euler21_small.ml

@@ -1,25 +0,0 @@
-let div_sum n =
-  let s = ref 1 in
-  let i = ref 2 in
-  while !i * !i <= n do
-    if n mod !i = 0 then begin
-      s := !s + !i;
-      let q = n / !i in
-      if q <> !i then s := !s + q
-    end;
-    i := !i + 1
-  done;
-  if n = 1 then 0 else !s
-
-let euler21 limit =
-  let total = ref 0 in
-  for a = 2 to limit do
-    let b = div_sum a in
-    if b <> a && b > a && b <= limit && div_sum b = a then
-      total := !total + a + b
-  done;
-  !total
-
-;;
-
-euler21 300

lib/ocaml/baseline/euler25.ml

@@ -1,17 +0,0 @@
-let euler25 n =
-  let a = ref 1 in
-  let b = ref 1 in
-  let i = ref 2 in
-  let target = ref 1 in
-  for _ = 1 to n - 1 do target := !target * 10 done;
-  while !b < !target do
-    let c = !a + !b in
-    a := !b;
-    b := c;
-    i := !i + 1
-  done;
-  !i
-
-;;
-
-euler25 12

lib/ocaml/baseline/euler28.ml

@@ -1,15 +0,0 @@
-let euler28 n =
-  let s = ref 1 in
-  let k = ref 1 in
-  for layer = 1 to (n - 1) / 2 do
-    let step = 2 * layer in
-    for _ = 1 to 4 do
-      k := !k + step;
-      s := !s + !k
-    done
-  done;
-  !s
-
-;;
-
-euler28 7

lib/ocaml/baseline/euler29_small.ml

@@ -1,14 +0,0 @@
-let euler29 n =
-  let h = Hashtbl.create 64 in
-  for a = 2 to n do
-    for b = 2 to n do
-      let p = ref 1 in
-      for _ = 1 to b do p := !p * a done;
-      Hashtbl.replace h !p ()
-    done
-  done;
-  Hashtbl.length h
-
-;;
-
-euler29 5

lib/ocaml/baseline/euler3.ml

@@ -1,15 +0,0 @@
-let largest_prime_factor n =
-  let m = ref n in
-  let factor = ref 2 in
-  let largest = ref 0 in
-  while !m > 1 do
-    if !m mod !factor = 0 then begin
-      largest := !factor;
-      m := !m / !factor
-    end else factor := !factor + 1
-  done;
-  !largest
-
-;;
-
-largest_prime_factor 13195

lib/ocaml/baseline/euler30_cube.ml

@@ -1,22 +0,0 @@
-let pow_digit_sum n p =
-  let m = ref n in
-  let s = ref 0 in
-  while !m > 0 do
-    let d = !m mod 10 in
-    let pd = ref 1 in
-    for _ = 1 to p do pd := !pd * d done;
-    s := !s + !pd;
-    m := !m / 10
-  done;
-  !s
-
-let euler30 p limit =
-  let total = ref 0 in
-  for n = 2 to limit do
-    if pow_digit_sum n p = n then total := !total + n
-  done;
-  !total
-
-;;
-
-euler30 3 999

lib/ocaml/baseline/euler34_small.ml

@@ -1,24 +0,0 @@
-let fact n =
-  let r = ref 1 in
-  for i = 2 to n do r := !r * i done;
-  !r
-
-let digit_fact_sum n =
-  let m = ref n in
-  let s = ref 0 in
-  while !m > 0 do
-    s := !s + fact (!m mod 10);
-    m := !m / 10
-  done;
-  !s
-
-let euler34 limit =
-  let total = ref 0 in
-  for n = 3 to limit do
-    if digit_fact_sum n = n then total := !total + n
-  done;
-  !total
-
-;;
-
-euler34 2000

lib/ocaml/baseline/euler36.ml

@@ -1,41 +0,0 @@
-let pal_dec n =
-  let s = string_of_int n in
-  let len = String.length s in
-  let p = ref true in
-  for i = 0 to len / 2 - 1 do
-    if s.[i] <> s.[len - 1 - i] then p := false
-  done;
-  !p
-
-let to_binary n =
-  if n = 0 then "0"
-  else
-    let buf = Buffer.create 32 in
-    let m = ref n in
-    let stack = ref [] in
-    while !m > 0 do
-      stack := (!m mod 2) :: !stack;
-      m := !m / 2
-    done;
-    List.iter (fun d -> Buffer.add_string buf (string_of_int d)) !stack;
-    Buffer.contents buf
-
-let pal_bin n =
-  let s = to_binary n in
-  let len = String.length s in
-  let p = ref true in
-  for i = 0 to len / 2 - 1 do
-    if s.[i] <> s.[len - 1 - i] then p := false
-  done;
-  !p
-
-let euler36 limit =
-  let sum = ref 0 in
-  for n = 1 to limit - 1 do
-    if pal_dec n && pal_bin n then sum := !sum + n
-  done;
-  !sum
-
-;;
-
-euler36 1000

lib/ocaml/baseline/euler40_small.ml

@@ -1,22 +0,0 @@
-let euler40 () =
-  let buf = Buffer.create 4096 in
-  let len = ref 0 in
-  let i = ref 1 in
-  while !len < 1500 do
-    let s = string_of_int !i in
-    Buffer.add_string buf s;
-    len := !len + String.length s;
-    i := !i + 1
-  done;
-  let s = Buffer.contents buf in
-  let prod = ref 1 in
-  let positions = [1; 10; 100; 1000] in
-  List.iter (fun p ->
-    let c = s.[p - 1] in
-    prod := !prod * (Char.code c - Char.code '0')
-  ) positions;
-  !prod
-
-;;
-
-euler40 ()

lib/ocaml/baseline/euler4_small.ml

@@ -1,21 +0,0 @@
-let is_pal n =
-  let s = string_of_int n in
-  let len = String.length s in
-  let p = ref true in
-  for i = 0 to len / 2 - 1 do
-    if s.[i] <> s.[len - 1 - i] then p := false
-  done;
-  !p
-
-let euler4 lo hi =
-  let m = ref 0 in
-  for a = lo to hi do
-    for b = a to hi do
-      let p = a * b in
-      if p > !m && is_pal p then m := p
-    done
-  done;
-  !m
-;;
-
-euler4 10 99

lib/ocaml/baseline/euler5.ml

@@ -1,11 +0,0 @@
-let rec gcd a b = if b = 0 then a else gcd b (a mod b)
-let lcm a b = a * b / gcd a b
-let euler5 n =
-  let r = ref 1 in
-  for i = 2 to n do
-    r := lcm !r i
-  done;
-  !r
-;;
-
-euler5 20

lib/ocaml/baseline/euler6.ml

@@ -1,12 +0,0 @@
-let euler6 n =
-  let sum = ref 0 in
-  let sum_sq = ref 0 in
-  for i = 1 to n do
-    sum := !sum + i;
-    sum_sq := !sum_sq + i * i
-  done;
-  !sum * !sum - !sum_sq
-
-;;
-
-euler6 100

lib/ocaml/baseline/euler7.ml

@@ -1,22 +0,0 @@
-let nth_prime n =
-  let count = ref 0 in
-  let i = ref 1 in
-  let result = ref 0 in
-  while !count < n do
-    i := !i + 1;
-    let p = ref true in
-    let j = ref 2 in
-    while !j * !j <= !i && !p do
-      if !i mod !j = 0 then p := false;
-      j := !j + 1
-    done;
-    if !p then begin
-      count := !count + 1;
-      if !count = n then result := !i
-    end
-  done;
-  !result
-
-;;
-
-nth_prime 100

lib/ocaml/baseline/euler9.ml

@@ -1,17 +0,0 @@
-let euler9 () =
-  let result = ref 0 in
-  for a = 1 to 333 do
-    let num = 500000 - 1000 * a in
-    let den = 1000 - a in
-    if num mod den = 0 then begin
-      let b = num / den in
-      if b > a then
-        let c = 1000 - a - b in
-        if c > b then result := a * b * c
-    end
-  done;
-  !result
-
-;;
-
-euler9 ()

lib/ocaml/baseline/exception_handle.ml

@@ -1,17 +0,0 @@
-(* Baseline: exception declaration + raise + try-with *)
-exception NegArg of int ;;
-let safe_sqrt n =
-  if n < 0 then raise (NegArg n)
-  else
-    begin
-      let rec find_sqrt i =
-        if i * i > n then i - 1
-        else find_sqrt (i + 1)
-      in find_sqrt 0
-    end ;;
-let result =
-  try
-    safe_sqrt 16
-  with
-  | NegArg _ -> 0 ;;
-result

lib/ocaml/baseline/exception_user.ml

@@ -1,16 +0,0 @@
-exception Negative of int
-
-let safe_sqrt n =
-  if n < 0 then raise (Negative n)
-  else
-    let g = ref 1 in
-    while !g * !g < n do g := !g + 1 done;
-    !g
-
-let try_sqrt n =
-  try safe_sqrt n with
-  | Negative x -> -x
-
-;;
-
-try_sqrt 16 + try_sqrt 25 + try_sqrt (-7) + try_sqrt 100

lib/ocaml/baseline/expected.json

@@ -1,207 +0,0 @@
-{
-  "abundant.ml": 21,
-  "activity_select.ml": 4,
-  "ackermann.ml": 125,
-  "adler32.ml": 300286872,
-  "anagram_check.ml": 2,
-  "anagram_groups.ml": 3,
-  "anagrams.ml": 3,
-  "atm.ml": 120,
-  "bag.ml": 3,
-  "bowling.ml": 167,
-  "bf_full.ml": 6,
-  "bisect.ml": 141,
-  "bigint_add.ml": 28,
-  "binary_heap.ml": 123456789,
-  "bipartite.ml": 4,
-  "bits.ml": 21,
-  "balance.ml": 3,
-  "bracket_match.ml": 5,
-  "base_n.ml": 17,
-  "bfs.ml": 6,
-  "bfs_grid.ml": 8,
-  "btree.ml": 39,
-  "brainfuck.ml": 75,
-  "bs_bounds.ml": 3211,
-  "bs_rotated.ml": -66,
-  "bsearch.ml": 7,
-  "caesar.ml": 215,
-  "calc.ml": 13,
-  "catalan.ml": 42,
-  "closures.ml": 315,
-  "combinations.ml": 126,
-  "convex_hull.ml": 5,
-  "coin_change.ml": 6,
-  "coin_min.ml": 6,
-  "count_bits.ml": 319,
-  "count_change.ml": 406,
-  "count_paths_dag.ml": 3,
-  "count_inversions.ml": 12,
-  "count_palindromes.ml": 9,
-  "count_subarrays_k.ml": 7,
-  "csv.ml": 10,
-  "daily_temperatures.ml": 10,
-  "egg_drop.ml": 8,
-  "dijkstra.ml": 7,
-  "dp_word_break.ml": 4,
-  "distinct_subseq.ml": 3,
-  "exception_handle.ml": 4,
-  "exception_user.ml": 26,
-  "euler1.ml": 233168,
-  "euler16.ml": 26,
-  "euler10.ml": 1060,
-  "euler14.ml": 97,
-  "euler2.ml": 4613732,
-  "euler21_small.ml": 504,
-  "euler25.ml": 55,
-  "euler28.ml": 261,
-  "euler29_small.ml": 15,
-  "euler30_cube.ml": 1301,
-  "euler34_small.ml": 145,
-  "euler36.ml": 1772,
-  "euler40_small.ml": 15,
-  "euler3.ml": 29,
-  "euler4_small.ml": 9009,
-  "euler5.ml": 232792560,
-  "euler6.ml": 25164150,
-  "euler7.ml": 541,
-  "euler9.ml": 31875000,
-  "expr_eval.ml": 16,
-  "expr_simp.ml": 22,
-  "factorial.ml": 3628800,
-  "fenwick_tree.ml": 228,
-  "fib_doubling.ml": 102334155,
-  "fib_mod.ml": 391360,
-  "fraction.ml": 7,
-  "frequency.ml": 5,
-  "gas_station.ml": 3,
-  "gcd_lcm.ml": 60,
-  "gray_code.ml": 136,
-  "grep_count.ml": 3,
-  "grid_paths.ml": 210,
-  "group_consec.ml": 53,
-  "hailstone.ml": 111,
-  "harshad.ml": 33,
-  "hamming.ml": 4,
-  "hanoi.ml": 1023,
-  "hist.ml": 75,
-  "house_robber.ml": 22,
-  "histogram_area.ml": 10,
-  "huffman.ml": 224,
-  "int_sqrt.ml": 1027,
-  "interval_overlap.ml": 6,
-  "is_prime.ml": 25,
-  "island_count.ml": 5,
-  "fizz_classifier.ml": 540,
-  "fizzbuzz.ml": 57,
-  "flatten_tree.ml": 28,
-  "flood_fill.ml": 7,
-  "floyd_cycle.ml": 8,
-  "floyd_warshall.ml": 9,
-  "lis.ml": 6,
-  "list_ops.ml": 30,
-  "lps_dp.ml": 7,
-  "lru_cache.ml": 499,
-  "luhn.ml": 2,
-  "magic_square.ml": 65,
-  "mat_mul.ml": 621,
-  "matrix_power.ml": 832040,
-  "max_path_tree.ml": 11,
-  "max_product3.ml": 300,
-  "max_run.ml": 5,
-  "mod_inverse.ml": 27,
-  "josephus.ml": 11,
-  "json_pretty.ml": 24,
-  "kadane.ml": 6,
-  "kmp.ml": 5,
-  "kth_two.ml": 8,
-  "knapsack.ml": 36,
-  "lambda_calc.ml": 7,
-  "lcs.ml": 4,
-  "majority_vote.ml": 4,
-  "manacher.ml": 7,
-  "lev_iter.ml": 16,
-  "levenshtein.ml": 11,
-  "memo_fib.ml": 75025,
-  "mortgage.ml": 1073,
-  "mst_kruskal.ml": 11,
-  "merge_intervals.ml": 12,
-  "min_meeting_rooms.ml": 4,
-  "merge_sort.ml": 44,
-  "merge_two.ml": 441,
-  "min_cost_path.ml": 12,
-  "min_jumps.ml": 4,
-  "min_subarr_target.ml": 2,
-  "module_use.ml": 3,
-  "monotonic.ml": 4,
-  "newton_sqrt.ml": 1414,
-  "next_greater.ml": 153,
-  "next_permutation.ml": 119,
-  "number_words.ml": 106,
-  "mutable_record.ml": 10,
-  "option_match.ml": 5,
-  "palindrome.ml": 4,
-  "palindrome_part.ml": 1,
-  "palindrome_sum.ml": 49500,
-  "paren_depth.ml": 7,
-  "partition.ml": 3025,
-  "partition_count.ml": 176,
-  "pancake_sort.ml": 910,
-  "pascal.ml": 252,
-  "peano.ml": 30,
-  "perfect.ml": 3,
-  "permutations_gen.ml": 12,
-  "pi_leibniz.ml": 314,
-  "prefix_sum.ml": 66,
-  "pretty_table.ml": 64,
-  "poly_stack.ml": 5,
-  "polygon_area.ml": 32,
-  "pow_mod.ml": 738639,
-  "powerset_target.ml": 20,
-  "prime_factors.ml": 17,
-  "pythagorean.ml": 16,
-  "queens.ml": 2,
-  "quickselect.ml": 5,
-  "quicksort.ml": 44,
-  "radix_sort.ml": 802002,
-  "roman.ml": 44,
-  "rolling_hash.ml": 6,
-  "regex_simple.ml": 7,
-  "reverse_int.ml": 54329,
-  "rpn.ml": 9,
-  "run_decode.ml": 21,
-  "run_length.ml": 11,
-  "safe_div.ml": 20,
-  "segment_tree.ml": 4232,
-  "shuffle.ml": 55,
-  "simpson_int.ml": 10000,
-  "stable_unique.ml": 46,
-  "stock_two.ml": 6,
-  "subseq_check.ml": 3,
-  "tail_factorial.ml": 479001600,
-  "task_scheduler.ml": 7,
-  "tarjan_scc.ml": 4,
-  "subset_sum.ml": 8,
-  "tic_tac_toe.ml": 1,
-  "topo_dfs.ml": 24135,
-  "topo_sort.ml": 6,
-  "wildcard_match.ml": 6,
-  "word_freq.ml": 8,
-  "xor_cipher.ml": 601,
-  "zerosafe.ml": 28,
-  "zigzag.ml": 55,
-  "zip_unzip.ml": 1000,
-  "sieve.ml": 15,
-  "sum_squares.ml": 385,
-  "tree_depth.ml": 4,
-  "trapping_rain.ml": 6,
-  "triangle.ml": 11,
-  "trie.ml": 6,
-  "triangle_div.ml": 120,
-  "twosum.ml": 5,
-  "union_find.ml": 4,
-  "unique_paths_obs.ml": 3,
-  "unique_set.ml": 9,
-  "validate.ml": 417,
-  "word_count.ml": 3
-}

lib/ocaml/baseline/expr_eval.ml

@@ -1,19 +0,0 @@
-(* Baseline: a tiny expression evaluator using ADTs + match *)
-type expr =
-  | Lit of int
-  | Add of expr * expr
-  | Mul of expr * expr
-  | Neg of expr
-;;
-
-let rec eval e =
-  match e with
-  | Lit n -> n
-  | Add (a, b) -> eval a + eval b
-  | Mul (a, b) -> eval a * eval b
-  | Neg x -> 0 - eval x
-;;
-
-(* (1 + 2) * (3 + 4) - 5 = 21 - 5 = 16 *)
-eval
-  (Add (Mul (Add (Lit 1, Lit 2), Add (Lit 3, Lit 4)), Neg (Lit 5)))

lib/ocaml/baseline/expr_simp.ml

@@ -1,33 +0,0 @@
-type expr =
-  | Num of int
-  | Add of expr * expr
-  | Mul of expr * expr
-
-let rec simp e =
-  match e with
-  | Num n -> Num n
-  | Add (a, b) ->
-    (match (simp a, simp b) with
-     | (Num 0, x) -> x
-     | (x, Num 0) -> x
-     | (Num n, Num m) -> Num (n + m)
-     | (a', b') -> Add (a', b'))
-  | Mul (a, b) ->
-    (match (simp a, simp b) with
-     | (Num 0, _) -> Num 0
-     | (_, Num 0) -> Num 0
-     | (Num 1, x) -> x
-     | (x, Num 1) -> x
-     | (Num n, Num m) -> Num (n * m)
-     | (a', b') -> Mul (a', b'))
-
-let rec eval e =
-  match e with
-  | Num n -> n
-  | Add (a, b) -> eval a + eval b
-  | Mul (a, b) -> eval a * eval b
-
-;;
-
-let e = Add (Mul (Num 3, Num 5), Add (Num 0, Mul (Num 1, Num 7))) in
-eval (simp e)

lib/ocaml/baseline/factorial.ml

@@ -1,4 +0,0 @@
-(* Baseline: factorial via let-rec *)
-let rec fact n =
-  if n = 0 then 1 else n * fact (n - 1) ;;
-fact 10

lib/ocaml/baseline/fenwick_tree.ml

@@ -1,33 +0,0 @@
-let n = 8
-
-let bit = Array.make (n + 1) 0
-
-let lowbit i =
-  let r = ref 1 in
-  while !r * 2 <= i && i mod (!r * 2) = 0 do
-    r := !r * 2
-  done;
-  !r
-
-let rec update i delta =
-  if i <= n then begin
-    bit.(i) <- bit.(i) + delta;
-    update (i + lowbit i) delta
-  end
-
-let rec prefix_sum i =
-  if i <= 0 then 0
-  else bit.(i) + prefix_sum (i - lowbit i)
-
-let range_sum l r = prefix_sum r - prefix_sum (l - 1)
-
-;;
-
-let a = [| 1; 3; 5; 7; 9; 11; 13; 15 |] in
-for i = 0 to n - 1 do
-  update (i + 1) a.(i)
-done;
-let total = prefix_sum n in
-update 1 100;
-let after = prefix_sum n in
-total + after

lib/ocaml/baseline/fib_doubling.ml

@@ -1,14 +0,0 @@
-let rec fib_pair n =
-  if n = 0 then (0, 1)
-  else
-    let (a, b) = fib_pair (n / 2) in
-    let c = a * (2 * b - a) in
-    let d = a * a + b * b in
-    if n mod 2 = 0 then (c, d)
-    else (d, c + d)
-
-let fib n = let (f, _) = fib_pair n in f
-
-;;
-
-fib 40