datalog: dl-eval source + query convenience (181/181)

Single-call entry: dl-eval source-string query-string parses
both, builds a db via dl-program, saturates implicitly, runs
the query (extracted from the parsed `?- ...` clause), and
returns the substitution list.

Most user-friendly path:
  (dl-eval "parent(a, b). ..." "?- ancestor(a, X).")

2 new api tests cover ancestor and multi-goal usage.

lib/datalog/api.sx

@@ -149,6 +149,26 @@
         (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)))))))
+
 (define
   dl-rule-head-rels
   (fn

lib/datalog/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "datalog",
-  "total_passed": 179,
+  "total_passed": 181,
   "total_failed": 0,
-  "total": 179,
+  "total": 181,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
@@ -12,8 +12,8 @@
     {"name":"semi_naive","passed":8,"failed":0,"total":8},
     {"name":"negation","passed":10,"failed":0,"total":10},
     {"name":"aggregates","passed":16,"failed":0,"total":16},
-    {"name":"api","passed":11,"failed":0,"total":11},
+    {"name":"api","passed":13,"failed":0,"total":13},
     {"name":"demo","passed":18,"failed":0,"total":18}
   ],
-  "generated": "2026-05-08T09:38:47+00:00"
+  "generated": "2026-05-08T09:40:51+00:00"
 }

lib/datalog/scoreboard.md

@@ -1,6 +1,6 @@
 # datalog scoreboard
 
-**179 / 179 passing** (0 failure(s)).
+**181 / 181 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -12,5 +12,5 @@
 | semi_naive | 8 | 8 | ok |
 | negation | 10 | 10 | ok |
 | aggregates | 16 | 16 | ok |
-| api | 11 | 11 | ok |
+| api | 13 | 13 | ok |
 | demo | 18 | 18 | ok |

lib/datalog/tests/api.sx

@@ -198,6 +198,21 @@
           (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-rule-from-list with no arrow → fact-style.
       (dl-api-test-set! "no arrow → fact-like rule"
         (let

plans/datalog-on-sx.md

@@ -284,6 +284,11 @@ large graphs.
 
 _Newest first._
 
+- 2026-05-08 — Convenience: `dl-eval source query-source`. Parses
+  both strings, builds a db, saturates, runs the query, returns
+  the substitution list. Single-call user-friendly entry. 2 new
+  api tests cover ancestor and multi-goal queries.
+
 - 2026-05-08 — Phase 6 stub: `dl-set-strategy! db strategy` and
   `dl-get-strategy db` user-facing hooks. Default `:semi-naive`;
   `:magic` is accepted but the actual transformation is deferred,