maude: mixfix surface-syntax printer (11 tests, 207 total)

lib/maude/pretty.sx — mau/term->maude renders internal prefix terms back
in Maude mixfix syntax driven by op forms; mau/red->maude / mau/rew->maude
reduce-then-render. Output now reads as idiomatic Maude.

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

lib/maude/pretty.sx

@@ -0,0 +1,82 @@
+;; lib/maude/pretty.sx — mixfix surface-syntax printer.
+;;
+;; term->str renders the internal prefix form (`_+_(s_(X), 0)`); this renders
+;; terms back in Maude mixfix surface syntax (`((s X) + 0)`), driven by the
+;; operator forms in the module signature. Fully parenthesised — unambiguous
+;; rather than minimal. Constants and unknown ops fall back to prefix form.
+
+(define
+  mau/render-forms
+  (fn
+    (m)
+    (let
+      ((tbl {}))
+      (for-each
+        (fn
+          (op)
+          (dict-set! tbl (get op :name) (mau/op-form (get op :name))))
+        (mau/module-ops m))
+      tbl)))
+
+(define
+  mau/render-args
+  (fn
+    (forms args)
+    (cond
+      ((empty? args) "")
+      ((empty? (rest args)) (mau/render-term forms (first args)))
+      (else
+        (str
+          (mau/render-term forms (first args))
+          ", "
+          (mau/render-args forms (rest args)))))))
+
+(define
+  mau/render-term
+  (fn
+    (forms t)
+    (cond
+      ((mau/var? t) (mau/vname t))
+      ((mau/app? t)
+        (let
+          ((form (get forms (mau/op t))) (args (mau/args t)))
+          (cond
+            ((empty? args) (mau/op t))
+            ((and form (= (get form :kind) "infix") (= (len args) 2))
+              (str
+                "("
+                (mau/render-term forms (nth args 0))
+                " "
+                (get form :token)
+                " "
+                (mau/render-term forms (nth args 1))
+                ")"))
+            ((and form (= (get form :kind) "prefix") (= (len args) 1))
+              (str
+                "("
+                (get form :token)
+                " "
+                (mau/render-term forms (first args))
+                ")"))
+            ((and form (= (get form :kind) "postfix") (= (len args) 1))
+              (str
+                "("
+                (mau/render-term forms (first args))
+                " "
+                (get form :token)
+                ")"))
+            (else (str (mau/op t) "(" (mau/render-args forms args) ")")))))
+      (else (str t)))))
+
+(define
+  mau/term->maude
+  (fn (m t) (mau/render-term (mau/render-forms m) t)))
+
+;; reduce / rewrite then render in surface syntax
+(define
+  mau/red->maude
+  (fn (m src) (mau/term->maude m (mau/creduce-term m src))))
+
+(define
+  mau/rew->maude
+  (fn (m src) (mau/term->maude m (mau/rewrite-term m src))))