From 282a3d3d06aaf2b85484a05d32f13cf0534d5c4d Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Fri, 8 May 2026 10:04:59 +0000
Subject: [PATCH] datalog: dl-eval-magic single-call magic-sets entry (206/206)

Symmetric to dl-eval but routes single-positive-literal queries
through dl-magic-query for goal-directed evaluation. Multi-literal
query bodies fall back to standard dl-query (magic-sets is wired
for single goals only).

  (dl-eval-magic source-string "?- ancestor(a, X).")

1 new api test.
---
 lib/datalog/api.sx          | 29 +++++++++++++++++++++++++++++
 lib/datalog/scoreboard.json |  8 ++++----
 lib/datalog/scoreboard.md   |  4 ++--
 lib/datalog/tests/api.sx    | 10 ++++++++++
 4 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/lib/datalog/api.sx b/lib/datalog/api.sx
index 872b2017..72cb9dfd 100644
--- a/lib/datalog/api.sx
+++ b/lib/datalog/api.sx
@@ -169,6 +169,35 @@
         (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)))))))))
+
 (define
   dl-rule-head-rels
   (fn
diff --git a/lib/datalog/scoreboard.json b/lib/datalog/scoreboard.json
index 9c238632..203984a5 100644
--- a/lib/datalog/scoreboard.json
+++ b/lib/datalog/scoreboard.json
@@ -1,8 +1,8 @@
 {
   "lang": "datalog",
-  "total_passed": 205,
+  "total_passed": 206,
   "total_failed": 0,
-  "total": 205,
+  "total": 206,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
@@ -12,9 +12,9 @@
     {"name":"semi_naive","passed":8,"failed":0,"total":8},
     {"name":"negation","passed":10,"failed":0,"total":10},
     {"name":"aggregates","passed":18,"failed":0,"total":18},
-    {"name":"api","passed":14,"failed":0,"total":14},
+    {"name":"api","passed":15,"failed":0,"total":15},
     {"name":"magic","passed":21,"failed":0,"total":21},
     {"name":"demo","passed":18,"failed":0,"total":18}
   ],
-  "generated": "2026-05-08T10:02:51+00:00"
+  "generated": "2026-05-08T10:04:46+00:00"
 }
diff --git a/lib/datalog/scoreboard.md b/lib/datalog/scoreboard.md
index 3ad41dc4..8af1890b 100644
--- a/lib/datalog/scoreboard.md
+++ b/lib/datalog/scoreboard.md
@@ -1,6 +1,6 @@
 # datalog scoreboard
 
-**205 / 205 passing** (0 failure(s)).
+**206 / 206 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -12,6 +12,6 @@
 | semi_naive | 8 | 8 | ok |
 | negation | 10 | 10 | ok |
 | aggregates | 18 | 18 | ok |
-| api | 14 | 14 | ok |
+| api | 15 | 15 | ok |
 | magic | 21 | 21 | ok |
 | demo | 18 | 18 | ok |
diff --git a/lib/datalog/tests/api.sx b/lib/datalog/tests/api.sx
index 0431ed1f..809946df 100644
--- a/lib/datalog/tests/api.sx
+++ b/lib/datalog/tests/api.sx
@@ -213,6 +213,16 @@
           "?- p(X), q(X).")
         (list {:X 2} {:X 3}))
 
+      ;; 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)}))
+
       ;; Comprehensive integration: recursion + stratified negation
       ;; + aggregation + comparison composed in a single program.
       ;; (Uses _Anything as a regular var instead of `_` so the