artdag: maude-bridge dag<->term adapter + 14 round-trip tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/artdag/maude-bridge.sx

@@ -0,0 +1,118 @@
+; lib/artdag/maude-bridge.sx — adapter between an artdag effect DAG and maude terms.
+; A node {:op :inputs :params :commutative} <-> a maude (mau/app op (args...)).
+; Inputs become argument subterms (recursively from the DAG). A trailing
+; "artdag:meta" subterm carries the params (a write-to-string token) and the
+; commutativity flag, so the encoding is lossless and dag->term->dag is the
+; identity on canonical (content-id) form. Commutative ops map to maude AC
+; operators in the optimizer module, so input order is irrelevant there —
+; mirroring the content-id's order-insensitivity for commutative nodes.
+;
+; maude (lib/maude) is a READ-ONLY consumed substrate: mau/app, mau/const,
+; mau/op, mau/args, mau/app? are its term constructors/accessors.
+
+; ---- list helpers (no host last/but-last) ----
+
+(define
+  artdag/mb-last
+  (fn
+    (xs)
+    (if (empty? (rest xs)) (first xs) (artdag/mb-last (rest xs)))))
+
+(define
+  artdag/mb-but-last
+  (fn
+    (xs)
+    (if
+      (empty? (rest xs))
+      (list)
+      (cons (first xs) (artdag/mb-but-last (rest xs))))))
+
+; ---- params <-> token ----
+; params are keyword-keyed dicts; write-to-string/read round-trips them
+; (key order may differ but the dicts compare structurally equal).
+
+(define artdag/mb-meta-op "artdag:meta")
+
+(define artdag/params->token (fn (params) (write-to-string params)))
+
+(define artdag/token->params (fn (token) (read (open-input-string token))))
+
+(define
+  artdag/mb-meta-term
+  (fn
+    (params commutative)
+    (mau/app
+      artdag/mb-meta-op
+      (list
+        (mau/const (artdag/params->token params))
+        (mau/const (if commutative "c" "n"))))))
+
+(define
+  artdag/mb-meta-term?
+  (fn (t) (and (mau/app? t) (= (mau/op t) artdag/mb-meta-op))))
+
+; ---- dag -> term ----
+
+(define
+  artdag/node->term
+  (fn
+    (node input-terms)
+    (mau/app
+      (artdag/node-op node)
+      (concat
+        input-terms
+        (list
+          (artdag/mb-meta-term
+            (artdag/node-params node)
+            (get node :commutative)))))))
+
+(define
+  artdag/dag->term
+  (fn
+    (dag id)
+    (let
+      ((node (artdag/dag-get dag id)))
+      (artdag/node->term
+        node
+        (map (fn (in) (artdag/dag->term dag in)) (artdag/node-inputs node))))))
+
+; ---- term -> dag ----
+; build-entries with synthesized local names; artdag/build recomputes content-ids
+; (which are name-independent), so the reconstructed dag is identical on canonical
+; form. Shared subterms re-collapse to one node/id during build's dedup.
+
+(define artdag/term-meta (fn (t) (artdag/mb-last (mau/args t))))
+
+(define artdag/term-input-terms (fn (t) (artdag/mb-but-last (mau/args t))))
+
+(define
+  artdag/term-params
+  (fn
+    (t)
+    (artdag/token->params (mau/op (first (mau/args (artdag/term-meta t)))))))
+
+(define
+  artdag/term-commutative
+  (fn
+    (t)
+    (= "c" (mau/op (nth (mau/args (artdag/term-meta t)) 1)))))
+
+(define
+  artdag/term->build
+  (fn
+    (t counter acc)
+    (let
+      ((built (reduce (fn (st child) (let ((r (artdag/term->build child (get st :counter) (get st :acc)))) {:counter (get r :counter) :acc (get r :acc) :names (concat (get st :names) (list (get r :name)))})) {:counter counter :acc acc :names (list)} (artdag/term-input-terms t))))
+      (let ((my-name (str "mb" (get built :counter)))) {:name my-name :counter (+ (get built :counter) 1) :acc (concat (get built :acc) (list (list my-name (mau/op t) (get built :names) (artdag/term-params t) (artdag/term-commutative t))))}))))
+
+(define
+  artdag/term->entries
+  (fn (t) (get (artdag/term->build t 0 (list)) :acc)))
+
+(define artdag/term->dag (fn (t) (artdag/build (artdag/term->entries t))))
+
+; ---- round-trip convenience ----
+
+(define
+  artdag/mb-roundtrip
+  (fn (dag id) (artdag/term->dag (artdag/dag->term dag id))))